Questo lavoro è stato sostenuto da una sovvenzione FAPESP (15/06477-9).

1. Preparazione dell'estratto totale di lievito
<ol><li>Crescono le cellule di lievito esprimendo uno dei fattori di splicing fusi al TAP tag9 in 1 L YNB-glu media (Yeast Nitrogen Basis integrato con glucosio 2% m/v) con gli aminoacidi o le basi nucleiche appropriate, in questo caso adenina (20 μg/mL), leucina (30 μg/mL), triptofano (30 μg/mL), fino a OD600 = 1,0.</li>
	<li>Raccogliere le cellule dalla coltura da 1 L centrifugando in tre flaconi di centrifuga da 500 mL a 17.000 x g per 10 minuti a 4 °C e lavare due volte con 10 ml di acqua sterile fredda.</li>
	<li>Risospesso le cellule di lievito raccolte in 1/10 del volume cellulare del tampone freddo A (10 mmol L-1 HEPES pH = 7,9, 1,5 mmol L-1 MgCl2, 50 mmol L-1 KCl, 5% v / v glicerolo, 0,5 mmol L-1 DTT, edTA-free Protease Inhibitor Cocktail).</li>
	<li>Congelare piccole gocce di sospensione cellulare in azoto liquido. Le piccole gocce possono essere ottenute pipettando la soluzione cellulare rinsosciata e facendo cadere 50 μL direttamente nell'azoto liquido. ATTENZIONE: L'azoto liquido può causare lesioni a contatto con la pelle o gli occhi. Maneggiare utilizzando attrezzature di sicurezza appropriate. NOTA: il protocollo può essere messo in pausa qui. Le gocce congelate di sospensione cellulare possono essere conservate a -80 °C.</li>
	<li>Preparare i lasati di cellule di lievito macinando in un dispositivo Ball Mill attraverso sei cicli a 20 Hz / s per 3 minuti. NOTA: Dopo ogni ciclo, immergere il contenitore che ospita le celle congelate in azoto liquido per evitare la fusione. Il protocollo può essere messo in pausa qui. Gli estratti congelati possono essere conservati a -80 °C. Gli estratti di splicing del lievito possono anche essere preparati utilizzando omogeneizzatori per lisato sferoplasti10,o utilizzando mortaio e pestello11,12.</li>
	<li>Sciogliere l'estratto mettendo i tubi che li contengono in acqua a temperatura ambiente, agitando di tanto in tanto.</li>
	<li>Centrifugare estratti a 45.000 x g per 1 ora a 4 °C.</li>
	<li>Quantificare il contenuto proteico del surnatante eliminato con il metodo BCA13.</li>
	<li>Preparare aliquote degli estratti, congelarli rapidamente in azoto liquido e conservarli a -80 °C. NOTA: il protocollo può essere messo in pausa qui.</li>
</ol>2. Preparazione del gradiente di glicerolo
<ol><li>Preparare due soluzioni di glicerolo nel tampone A, una contenente il 10% v/v e l'altra contenente il 30% di glicerolo v/v.</li>
	<li>Aggiungere l'agente reticolante glutaraldeide allo 0,1% v/v nella soluzione di glicerolo al 30% v/v e mescolare per omogeneizzare. ATTENZIONE: Maneggiare la glutaraldeide all'interno della cappa aspirante utilizzando appositi dispositivi di sicurezza.</li>
	<li>Aggiungere 6 mL della soluzione fredda di glicerolo al 10% v/v sul fondo del tubo della centrifuga da 12 mL (14 x 89 mm).</li>
	<li>Aggiungere 6 mL della soluzione fredda di glicerolo al 30% v/v integrata con glutaraldeide con una siringa attaccata a un ago lungo fornito con il dispositivo Gradient Master nella parte inferiore del tubo, appena sotto la soluzione di glicerolo al 10% v/v. NOTA: In alternativa, la soluzione di glicerolo al 10% v/v può essere accuratamente pipettata sulla parte superiore della soluzione di glicerolo/glutaraldeide al 30% v/v.</li>
	<li>Utilizzare il dispositivo Master sfumatura per generare una sfumatura di densità continua. NOTA: nel dispositivo Gradient Master, i tubi vengono inseriti in un rack appropriato e ruotati brevemente, seguendo le raccomandazioni del produttore per determinare i parametri (tempo/angolo/velocità). In questo lavoro abbiamo usato: 2:25 min/81.5°/11 rpm.</li>
	<li>Aggiungere con attenzione 200 μL di un cuscino di glicerolo/tampone al 7% v/v sulla parte superiore poco prima dell'aggiunta degli estratti cellulari. NOTA: La concentrazione di glicerolo del cuscino deve essere inferiore alla soluzione di glicerolo meno concentrata utilizzata per creare il gradiente lineare.</li>
</ol>3. Centrifugazione degli estratti
<ol><li>Caricare circa 2 mg di proteine totali sulla parte superiore di ogni 12 mL gradiente lineare di glicerolo 10%-30% glutaraldeide con cuscino.</li>
	<li>Posizionare i tubi in un rotore a benna oscillante pre-raffreddato. NOTA: Maneggiare delicatamente i tubi per evitare la miscelazione prima dell'ultracentrifugazione.</li>
	<li>Centrifuga a 194.000 x g per 16 ore a 4 °C.</li>
	<li>Aliquotare ogni tubo da 12 mL in ventiquattro frazioni da 500 μL utilizzando un EconoSystem adattato o mediante pipettaggio attento. NOTA: un EconoSystem adattato è costituito da una pompa peristaltica, dal rilevatore UV e dal collettore di frazioni collegato al dispositivo di perforazione del tubo. Il profilo di sedimentazione può essere monitorato mediante la misurazione dell'assorbanza a 280 nm.</li>
	<li>Utilizzare una soluzione di glicerolo al 40% v/v attraverso la pompa peristaltica per spingere il gradiente del glicerolo del 10%-30% dal tubo al collettore di frazione. NOTA: il protocollo può essere messo in pausa qui. Conservare le frazioni a -80 °C fino all'uso.</li>
	<li>Caricare 50 μL di ogni frazione direttamente sulle membrane di nitrocellulosa su un dispositivo dot blot o slot blot. Rileva la proteina mediante immunoblot utilizzando anticorpi contro CBP (1:6.000, per rilevare la porzione CBP del tag TAP) e IgG anti-coniglio coniugato con perossidasi di rafano (1:15.000) come anticorpo secondario.</li>
</ol>

<ol>
	<li>Kastner, B., Will, C. L., Stark, H., L&#252;hrmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+insights+into+nuclear+pre-mRNA+splicing+in+higher+eukaryotes.">Structural insights into nuclear pre-mRNA splicing in higher eukaryotes.</a> Cold Spring Harbor Perspectives in Biology. 11 (11), 032417 (2019).</li><li>Yan, C., Wan, R., Shi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanisms+of+pre-mRNA+splicing+through+structural+biology+of+the+spliceosome.">Molecular mechanisms of pre-mRNA splicing through structural biology of the spliceosome.</a> Cold Spring Harbor Perspectives in Biology. 11 (1), 032409 (2019).</li><li>Cordin, O., Hahn, D., Beggs, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure,+function+and+regulation+of+spliceosomal+RNA+helicases.">Structure, function and regulation of spliceosomal RNA helicases.</a> Current Opinion in Cell Biology. 24, 431-438 (2012).</li><li>Kastner, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GraFix:+sample+preparation+for+single-particle+electron+cryomicroscopy.">GraFix: sample preparation for single-particle electron cryomicroscopy.</a> Nature Methods. 5 (1), 53-55 (2008).</li><li>Stark, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grafix:+stabilization+of+fragile+macromolecular+complexes+for+single+particle+cryo-EM.">Grafix: stabilization of fragile macromolecular complexes for single particle cryo-EM.</a> Methods in Enzymology. 481, 109-126 (2010).</li><li>Yan, C., Wan, R., Bai, R., Huang, G., Shi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+of+a+yeast+activated+spliceosome+at+3.5+&#197;+resolution.">Structure of a yeast activated spliceosome at 3.5 &#197; resolution.</a> Science. 353 (6302), 895-904 (2016).</li><li>Ohi, M. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomics+analysis+revelas+stable+multiprotein+complexes+in+both+fission+and+budding+yeasts+containing+Myb-related+Cdc5p/Cef1p,+novel+pre-mRNA+splicing+factors,+and+snRNAs.">Proteomics analysis revelas stable multiprotein complexes in both fission and budding yeasts containing Myb-related Cdc5p/Cef1p, novel pre-mRNA splicing factors, and snRNAs.</a> Molecular and Cellular Biology. 22 (7), 2011-2024 (2002).</li><li>Lourenco, R. F., Leme, A. F. P., Oliveira, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+analysis+of+yeast+mutant+RNA+exosome+complexes.">Proteomic analysis of yeast mutant RNA exosome complexes.</a> Journal of Proteome Research. 12 (12), 5912-5922 (2013).</li><li>Rigaut, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+generic+protein+purification+method+for+protein+complex+characterizatioin+and+proteome+exploration.">A generic protein purification method for protein complex characterizatioin and proteome exploration.</a> Nature Biotechnology. 17, 1030-1032 (1999).</li><li>Cheng, S. C., Newman, A., Lin, R. J., McFarland, G. D., Abelson, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+fractionation+of+yeast+splicing+extract.">Preparation and fractionation of yeast splicing extract.</a> Methods in Enzymology. 181, 89-96 (1990).</li><li>Umen, J. G., Guthrie, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+role+for+a+U5+snRNP+protein+in+3'+splice+site+selection.">A novel role for a U5 snRNP protein in 3' splice site selection.</a> Genes &amp; Development. 9, 855-868 (1995).</li><li>Dunn, E. A., Rader, S. D., Hertel, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+yeast+whole+cell+splicing+extract.">Preparation of yeast whole cell splicing extract.</a> Spliceosomal Pre-mRNA Splicing: Methods and Protocols. Methods in Molecular Biology. 1126, 123-135 (2014).</li><li>Hill, H. D., Straka, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+determination+using+bicinchoninic+acid+in+the+presence+of+sulfhydryl+reagents.">Protein determination using bicinchoninic acid in the presence of sulfhydryl reagents.</a> Analalytical Biochemistry. 170 (1), 203-208 (1988).</li><li>Cepeda, L. 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Gli autori non hanno conflitti di interesse.

Le interazioni proteina-proteina e acidi ribonucleici-proteina possono essere stabilizzate utilizzando agenti reticolanti. È importante che il complesso risultante sia stabile per resistere all'ultracentrifugazione sul gradiente di glicerolo. Inoltre, le condizioni del buffer dovrebbero consentire l'interazione, ma essere abbastanza rigorose da evitare binding non specifici. Negli esperimenti qui mostrati, abbiamo utilizzato una soluzione tampone già stabilita per le reazioni di splicing in vitro15</s...

Lo splicing è un processo altamente dinamico che richiede il legame e il rilascio di una moltitudine di fattori in modo coordinato. Questi fattori di splicing includono proteine leganti l'RNA, ATPasi, elicasi, protein chinasi e fosfatasi, ubiquitina ligases, tra gli altri1,2,3; e per consentire i riarrangiamenti molecolari, alcuni di questi fattori si legano molto transitoriamente ai sottocomplessi dello spliceosoma, rendendo molto impegnativo l'isolamento e l'identificazione di questi complessi intermedi RNP.
Qui, abbiamo usato il metodo Grafix4,5 per stabilizzare l'interazione del fattore di splicing del lievito Cwc24 con il complesso diatto B6 per consentire l'identificazione di altri fattori legati contemporaneamente a quel sottocomplesso e determinare se l'ubiquitina ligasi Prp19 svolge un ruolo nel legame o nel rilascio di Cwc24 al complesso Nineteen (NTC) e all'estremità 5' dell'intron prima dell'attivazione e della prima reazione di transesterificazione prende luogo. Il vantaggio di esporre le macromolecole ad una concentrazione crescente del reticolante lungo il gradiente glicerolo è che evita i collegamenti incrociati inter-complessi4,5e quindi, la formazione di aggregati.
Questo metodo è stato utilizzato come complemento ai saggi di coimmunoprecipitazione e pull-down proteici, che, pur consentendo l'isolamento di grandi complessi, potrebbero non essere affidabili per mantenere interazioni transitorie all'interno di grandi complessidinamici 7,8. L'uso di reagenti di fissazione nel gradiente del glicerolo stabilizza il legame di tali fattori, consentendo la conferma delle interazioni di proteine specifiche con sottocomplessi di splicing. Poiché il reticolante scelto era chimicamente irreversibile, le proteine presenti nelle frazioni recuperate sono state analizzate mediante dot blot dopo la centrifugazione a gradiente.

<table><tbody><tr><td>Anti-Calmodulin Binding Protein Epitope</td><td>Millipore</td><td>07-482</td><td></td></tr><tr><td>ECL anti-Rabbit IgG</td><td>GE Healthcare</td><td>NA934</td><td></td></tr><tr><td>EconoSystem</td><td>Bio-Rad</td><td>1-800-424-6723</td><td>Parts of the EconoSystem used: peristaltic pump, the UV detector and the fraction collector</td></tr><tr><td>EDTA-free Protease Inhibitor Cocktail</td><td>Roche</td><td>11873580001</td><td></td></tr><tr><td>Fraction Recovery System</td><td>Beckman Coulter</td><td>270-331580</td><td>Tube-perforating device that was connected to the parts of the EconoSystem</td></tr><tr><td>Gradient Master Model 107ip</td><td>Biocomp</td><td>107-201M</td><td></td></tr><tr><td>Mixer Mill MM 200</td><td>Retsch</td><td>207460001</td><td>Ball Mill device</td></tr><tr><td>Rotor F12-6x500Lex</td><td>Thermo Scientific</td><td>096-062375</td><td></td></tr><tr><td>Sorvall RC 6 Plus Centrifuge</td><td>Thermo Scientific</td><td>36-101-0816</td><td></td></tr><tr><td>Swinging Bucket Rotor P40ST</td><td>Hitachi</td><td></td><td></td></tr><tr><td>Ultracentrifuge CP 80 NX</td><td>Hitachi</td><td>901069</td><td></td></tr><tr><td>Ultra-Clear Centrifuge Tubes (14 x 89 mm)</td><td>Beckman Coulter</td><td>344059</td><td></td></tr></tbody></table>

utilization of grafix for the detection of transient interactors of saccharomyces cerevisiae spliceosome subcomplexes

Lo splicing pre-mRNA è un processo molto dinamico che coinvolge molti riarrangiamenti molecolari dei sottocomplessi dello spliceosoma durante l'assemblaggio, l'elaborazione dell'RNA e il rilascio dei componenti complessi. La centrifugazione a gradiente di glicerolo è stata utilizzata per la separazione di complessi proteici o RNP (RiboNucleoProtein) per studi funzionali e strutturali. Qui, descriviamo l'utilizzo di Grafix (Gradient Fixation), che è stato sviluppato per la prima volta per purificare e stabilizzare i complessi macromolecolari per la microscopia crioeletnica a singola particella, per identificare le interazioni tra i fattori di splicing che si legano transitoriamente al complesso spliceosoma. Questo metodo si basa sulla centrifugazione di campioni in una concentrazione crescente di un reagente di fissazione per stabilizzare i complessi. Dopo la centrifugazione degli estratti totali di lievito caricati su gradienti di glicerolo, le frazioni recuperate vengono analizzate mediante dot blot per l'identificazione dei sotto-complessi spliceosomiali e la determinazione della presenza di singoli fattori di splicing.

Per analizzare il profilo di sedimentazione di Cwc24-TAP e determinare se il metodo Grafix fosse efficace per stabilizzare il suo legame ai sottocomplessi di splicing, abbiamo separato estratti di lievito totali di cellule che esprimono Cwc24-TAP attraverso centrifugazione su gradienti di glicerolo, in presenza o assenza di glutaraldeide come agente reticolante. Campioni di ventiquattro frazioni da 500 μL sono stati poi analizzati mediante slot blot con anticorpo contro la porzione CBP del tag TAP. I risultati mostrano ...

Watch this Scientific Journal Video about Utilization of Grafix for the Detection of Transient Interactors of Saccharomyces cerevisiae Spliceosome Subcomplexes at JoVE.com

Utilization of Grafix for the Detection of Transient Interactors of Saccharomyces cerevisiae Spliceosome Subcomplexes

Qui, descriviamo l'utilizzo di Grafix (Gradient Fixation), una centrifugazione a gradiente di glicerolo in presenza di un reticolante, per identificare le interazioni tra fattori di splicing che si legano transitoriamente al complesso spliceosoma.

Utilizzo di Grafix per la rilevazione di interattori transitori di sottocomplessi di saccharomyces cerevisiae spliceosomi

Pre-mRNA splicing is a very dynamic process that involves many molecular rearrangements of the spliceosome subcomplexes during assembly, RNA processing, ...

utilization-grafix-for-detection-transient-interactors-saccharomyces

Universidad San Sebastian

Research

JoVE Journal

Biochemistry

Utilization of Grafix for the Detection of Transient Interactors of Saccharomyces cerevisiae Spliceosome Subcomplexes

3.5K Views.  University of Sao Paulo. Qui, descriviamo l'utilizzo di Grafix (Gradient Fixation), una centrifugazione a gradiente di glicerolo in presenza di un reticolante, per identificare le interazioni tra fattori di splicing che si legano transitoriamente al complesso spliceosoma.

Video: Utilization of Grafix for the Detection of Transient Interactors of Saccharomyces cerevisiae Spliceosome Subcomplexes

Single Molecule Fluorescence In Situ Hybridization (smFISH) Analysis in Budding Yeast Vegetative Growth and Meiosis

Single molecule fluorescence in situ hybridization (smFISH) is a powerful technique to study gene expression in single cells due to its ability to detect and count individual RNA molecules. Complementary to deep sequencing-based methods, smFISH provides information about the cell-to-cell variation in transcript abundance and the subcellular localization of a given RNA. Recently, we have used smFISH to study the expression of the gene&#160;NDC80&#160;during meiosis in budding yeast, in which two transcript isoforms exist and the short transcript isoform has its entire sequence shared with the long isoform. To confidently identify each transcript isoform, we optimized known smFISH protocols and obtained high consistency and quality of smFISH data for the samples acquired during budding yeast meiosis. Here, we describe this optimized protocol, the criteria that we use to determine whether high quality of smFISH data is obtained, and some tips for implementing this protocol in&#160;other yeast strains and growth conditions.

Single Molecule Fluorescence In Situ Hybridization smFISH Analysis in Budding Yeast Vegetative Growth and Meiosis

This single molecule fluorescence in situ hybridization protocol is optimized to quantify the number of RNA molecules in budding yeast during vegetative growth and meiosis.

Singola molecola l'ibridazione In Situ (smFISH) analisi in crescita vegetativa lievito germogliante e meiosi

Single molecule fluorescence in situ hybridization (smFISH) is a powerful technique to study gene expression in single cells due to its ability to detect ...

Ricerca

Genetica

A Deep-sequencing-assisted, Spontaneous Suppressor Screen in the Fission Yeast Schizosaccharomyces pombe

A genetic screen for mutant alleles that suppress phenotypic defects caused by a mutation is a powerful approach to identify genes that belong to closely related biochemical pathways. Previous methods such as the Synthetic Genetic Array (SGA) analysis, and random mutagenesis techniques using ultraviolet (UV) or chemicals like ethyl methanesulfonate (EMS) or N-ethyl-N- nitrosourea (ENU), have been widely used but are often costly and laborious. Also, these mutagen-based screening methods are frequently associated with severe side effects on the organism, inducing multiple mutations that add to the complexity of isolating the suppressors. Here, we present a simple and effective protocol to identify suppressor mutations in mutants which confer a growth defect in Schizosaccharomyces pombe. The fitness of cells with a growth deficiency in standard rich liquid media or synthetic liquid media can be monitored for recovery using an automated 96-well plate reader over an extended period. Once a cell acquires a suppressor mutation in the culture, its descendants outcompete those of the parental cells. The recovered cells that have a competitive growth advantage over the parental cells can then be isolated and backcrossed with the parental cells. The suppressor mutations are then identified using whole-genome sequencing. Using this approach, we have successfully isolated multiple suppressors that alleviate the severe growth defects caused by loss of Elf1, an AAA+ family ATPase that is important in nuclear mRNA transport and maintenance of genomic stability. There are currently over 400 genes in S. pombe with mutants conferring a growth defect. As many of these genes are uncharacterized, we propose that our method will hasten the identification of novel functional interactions with this user-friendly, high-throughput approach.

A Deep-sequencing-assisted, Spontaneous Suppressor Screen in the Fission Yeast Schizosaccharomyces pombe

We present a simple suppressor screen protocol in fission yeast. This method is efficient, mutagen-free, and&#160; selective&#160; for&#160; mutations that&#160; often&#160; occur at&#160; &#160;a&#160; single&#160; genomic&#160; locus.&#160; The protocol is suitable for isolating suppressors that alleviate growth defects in liquid culture that are caused by a mutation or a drug.

Una schermata di soppressore Deep-sequenziamento-assistita, spontanea nel lievito a fissione Schizosaccharomyces pombe

A genetic screen for mutant alleles that suppress phenotypic defects caused by a mutation is a powerful approach to identify genes that belong to closely ...

Identification of protein complexes with quantitative proteomics in S. cerevisiae

Lipids are the building blocks of cellular membranes that function as barriers and in compartmentalization of cellular processes, and recently, as important intracellular signalling molecules. However, unlike proteins, lipids are small hydrophobic molecules that traffic primarily by poorly described nonvesicular routes, which are hypothesized to occur at membrane contact sites (MCSs). MCSs are regions where the endoplasmic reticulum (ER) makes direct physical contact with a partnering organelle, e.g., plasma membrane (PM). The ER portion of ER-PM MCSs is enriched in lipid-synthesizing enzymes, suggesting that lipid synthesis is directed to these sites and implying that MCSs are important for lipid traffic. Yeast is an ideal model to study ER-PM MCSs because of their abundance, with over 1000 contacts per cell, and their conserved nature in all eukaryotes. Uncovering the proteins that constitute MCSs is critical to understanding how lipids traffic is accomplished in cells, and how they act as signaling molecules. We have found that an ER called Scs2p localize to ER-PM MCSs and is important for their formation. We are focused on uncovering the molecular partners of Scs2p. Identification of protein complexes traditionally relies on first resolving purified protein samples by gel electrophoresis, followed by in-gel digestion of protein bands and analysis of peptides by mass spectrometry. This often limits the study to a small subset of proteins. Also, protein complexes are exposed to denaturing or non-physiological conditions during the procedure. To circumvent these problems, we have implemented a large-scale quantitative proteomics technique to extract unbiased and quantified data. We use stable isotope labeling with amino acids in cell culture (SILAC) to incorporate staple isotope nuclei in proteins in an untagged control strain. Equal volumes of tagged culture and untagged, SILAC-labeled culture are mixed together and lysed by grinding in liquid nitrogen. We then carry out an affinity purification procedure to pull down protein complexes. Finally, we precipitate the protein sample, which is ready for analysis by high-performance liquid chromatography/ tandem mass spectrometry. Most importantly, proteins in the control strain are labeled by the heavy isotope and will produce a mass/ charge shift that can be quantified against the unlabeled proteins in the bait strain. Therefore, contaminants, or unspecific binding can be easily eliminated. By using this approach, we have identified several novel proteins that localize to ER-PM MCSs. Here we present a detailed description of our approach. 

Here we describe a new quantitative proteomics technique for identifying protein complexes in Saccharomyces cerevisiae. In this study, we have used the SILAC method together with affinity purification followed by tandem mass spectrometry to identify with high specificity the binding partners of an ER protein, Scs2p.

L&#39;identificazione di complessi proteici con la proteomica quantitativa in S. cerevisiae

Lipids are the building blocks of cellular membranes that function as barriers and in compartmentalization of cellular processes, and recently, as ...

Biologia

ACT1-CUP1 Assays Determine the Substrate-Specific Sensitivities of Spliceosomal Mutants in Budding Yeast

Mutations introduced in the spliceosome or its substrate have significantly contributed to our understanding of the intricacies of spliceosomal function. Whether disease-related or functionally selected, many of these mutations have been studied using growth assays in the model organism Saccharomyces cerevisiae (yeast). The splicing-specific copper growth assay, or ACT1-CUP1 assay, provides a comprehensive analysis of mutation at the phenotypic level. The ACT1-CUP1 assay utilizes reporters that confer copper tolerance when correctly spliced. Thus, in the presence of copper, changes in yeast viability correlate to changes in mRNA production through splicing. In a typical experiment, the yeast spliceosome is challenged with different non-consensus splicing reporters and the splicing factor mutation of interest to detect any synergetic or antithetical impact on splicing. Here a full description of copper plate preparation, plating of yeast cells, and data evaluation are given. A selection of complimentary experiments is described, highlighting the versatility of the ACT1-CUP1 reporters. The ACT1-CUP1 assay is a handy tool in the splicing toolbox thanks to the direct read-out of mutational effect(s) and the comparative possibilities from the continuing use in the field.

The ACT1-CUP1 assay, a copper growth assay, provides a quick readout of precursor messenger RNA (pre-mRNA) splicing and the impact mutant splicing factors have on spliceosomal function. This study provides a protocol and highlights the customization possible to address the splicing question of interest.

I saggi ACT1-CUP1 determinano le sensibilità specifiche del substrato dei mutanti spliceosomi nel lievito in erba

Mutations introduced in the spliceosome or its substrate have significantly contributed to our understanding of the intricacies of spliceosomal function. ...

Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae

DNA damage, including DNA double-stranded breaks and inter-strand cross-links, incurred during the S and G2 phases of the cell cycle can be repaired by homologous recombination (HR). In addition, HR represents an important mechanism of replication fork rescue following stalling or collapse. The regulation of the many reversible and irreversible steps of this complex pathway promotes its fidelity. The physical analysis of the recombination intermediates formed during HR enables the characterization of these controls by various nucleoprotein factors and their interactors. Though there are well-established methods to assay specific events and intermediates in the recombination pathway, the detection of D-loop formation and extension, two critical steps in this pathway, has proved challenging until recently. Here, efficient methods for detecting key events in the HR pathway, namely DNA double-stranded break formation, D-loop formation, D-loop extension, and the formation of products via break-induced replication (BIR) in Saccharomyces cerevisiae are described. These assays detect their relevant recombination intermediates and products with high sensitivity and are independent of cellular viability. The detection of D-loops, D-loop extension, and the BIR product is based on proximity ligation. Together, these assays allow for the study of the kinetics of HR at the population level to finely address the functions of HR proteins and regulators at significant steps in the pathway.

Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae

The D-loop capture (DLC) and D-loop extension (DLE) assays utilize the principle of proximity ligation together with quantitative PCR to quantify D-loop formation, D-loop extension, and product formation at the site of an inducible double-stranded break in Saccharomyces cerevisiae.

Individuazione di intermedi di ricombinazione omologhi tramite legatura di prossimità e PCR quantitativa in Saccharomyces cerevisiae

DNA damage, including DNA double-stranded breaks and inter-strand cross-links, incurred during the S and G2 phases of the cell cycle can be repaired by ...

Complementation of Splicing Activity by a Galectin-3 - U1 snRNP Complex on Beads

Classic depletion-reconstitution experiments indicate that galectin-3 is a required splicing factor in nuclear extracts. The mechanism of incorporation of galectin-3 into the splicing pathway is addressed in this paper. Sedimentation of HeLa cell nuclear extracts on 12%-32% glycerol gradients yields fractions enriched in an endogenous ~10S particle that contains galectin-3 and U1 snRNP. We now describe a protocol to deplete nuclear extracts of U1 snRNP with concomitant loss of splicing activity. Splicing activity in the U1-depleted extract can be reconstituted by the galectin-3 - U1 snRNP particle trapped on agarose beads covalently coupled with anti-galectin-3 antibodies. The results indicate that the galectin-3 - U1 snRNP - pre-mRNA ternary complex is a functional E complex leading to intermediates and products of the splicing reaction and that galectin-3 enters the splicing pathway through its association with U1 snRNP. The scheme of using complexes affinity- or immuno-selected on beads to reconstitute splicing activity in extracts depleted of a specific splicing factor may be generally applicable to other systems.

This article describes the experimental procedures for (a) depletion of U1 snRNP from nuclear extracts, with concomitant loss of splicing activity; and (b) reconstitution of splicing activity in the U1-depleted extract by galectin-3 - U1 snRNP particles bound to beads covalently coupled with anti-galectin-3 antibodies.

Complementazione dell'attività di splicing da parte di un complesso snRNP Galectin-3 - U1 su perline

Classic depletion-reconstitution experiments indicate that galectin-3 is a required splicing factor in nuclear extracts. The mechanism of incorporation of ...

Biochimica

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for using FISH to quantify the number of mRNAs in single yeast cells. Cells can be grown in any condition of interest and then fixed and made permeable. Subsequently, multiple single-stranded deoxyoligonucleotides conjugated to fluorescent dyes are used to label and visualize mRNAs. Diffraction-limited fluorescence from single mRNA molecules is quantified using a spot-detection algorithm to identify and count the number of mRNAs per cell. While the more standard quantification methods of northern blots, RT-PCR and gene expression microarrays provide information on average mRNAs in the bulk population, FISH facilitates both the counting and localization of these mRNAs in single cells at single-molecule resolution.

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

This protocol describes an experimental procedure for performing Fluorescence in situ Hybridization (FISH) for counting mRNAs in single cells at single-molecule resolution.

Visualizzazione e l&#39;analisi di molecole di mRNA mediante fluorescenza<em&gt; In Situ</em&gt; Ibridazione in<em&gt; Saccharomyces cerevisiae</em

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for ...

Rapid Identification of Chemical Genetic Interactions in Saccharomyces cerevisiae

Determining the mode of action of bioactive chemicals is of interest to a broad range of academic, pharmaceutical, and industrial scientists. Saccharomyces cerevisiae, or budding yeast, is a model eukaryote for which a complete collection of ~6,000 gene deletion mutants and hypomorphic essential gene mutants are commercially available. These collections of mutants can be used to systematically detect chemical-gene interactions, i.e. genes necessary to tolerate a chemical. This information, in turn, reports on the likely mode of action of the compound. Here we describe a protocol for the rapid identification of chemical-genetic interactions in budding yeast. We demonstrate the method using the chemotherapeutic agent 5-fluorouracil (5-FU), which has a well-defined mechanism of action. Our results show that the nuclear TRAMP RNA exosome and DNA repair enzymes are needed for proliferation in the presence of 5-FU, which is consistent with previous microarray based bar-coding chemical genetic approaches and the knowledge that 5-FU adversely affects both RNA and DNA metabolism. The required validation protocols of these high-throughput screens are also described.

Rapid Identification of Chemical Genetic Interactions in Saccharomyces cerevisiae

Here we present a cost-effective method for defining chemical-genetic interactions in budding yeast. The approach is built on fundamental techniques in yeast molecular biology and is well suited for the mechanistic interrogation of small to medium collections of chemicals and other media environments.

Rapida identificazione dei chimici genetici Interactions in<em&gt; Saccharomyces cerevisiae</em

Determining the mode of action of bioactive chemicals is of interest to a broad range of academic, pharmaceutical, and industrial scientists. ...

Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells

Rapid responses involving fast redistribution of messenger(m)RNA and alterations of mRNA translation are pertinent to ongoing homeostatic adjustments of the cells. These adjustments are critical to eukaryotic cell survivability and &#39;damage control&#39; during fluctuating nutrient and salinity levels, temperature, and various chemical and radiation stresses. Due to the highly dynamic nature of the RNA-level responses, and the instability of many of the RNA:RNA and RNA:protein intermediates, obtaining a meaningful snapshot of the cytoplasmic RNA state is only possible with a limited number of methods. Transcriptome-wide, RNA-seq-based ribosome profiling-type experiments are among the most informative sources of data for the control of translation. However, absence of a uniform RNA and RNA:protein intermediate stabilization can lead to different biases, particularly in the fast-paced cellular response pathways. In this article, we provide a detailed protocol of rapid fixation applicable to eukaryotic cells of different permeability, to aid in RNA and RNA:protein intermediate stabilization. We further provide examples of isolation of the stabilized RNA:protein complexes based on their co-sedimentation with ribosomal and poly(ribo)somal fractions. The separated stabilized material can be subsequently used as part of ribosome profiling-type experiments, such as in Translation Complex Profile sequencing (TCP-seq) approach and its derivatives. Versatility of the TCP-seq-style methods has now been demonstrated by the applications in a variety of organisms and cell types. The stabilized complexes can also be additionally affinity-purified and imaged using electron microscopy, separated into different poly(ribo)somal fractions and subjected to RNA sequencing, owing to the ease of the crosslink reversal. Therefore, methods based on snap-chilling and formaldehyde fixation, followed by the sedimentation-based or other type of RNA:protein complex enrichment, can be of particular interest in investigating finer details of rapid RNA:protein complex dynamics in live cells.

Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells

We present a technique to rapidly stabilize translational (protein biosynthesis) complexes with formaldehyde crosslinking in live yeast and mammalian cells. The approach enables dissecting transient intermediates and dynamic RNA:protein interactions. The crosslinked complexes can be used in multiple downstream applications such as in deep sequencing-based profiling methods, microscopy, and mass-spectrometry.

Rapida fissazione in vivo e isolamento dei complessi traslazionali dalle cellule eucariotiche

Rapid responses involving fast redistribution of messenger(m)RNA and alterations of mRNA translation are pertinent to ongoing homeostatic adjustments of ...

Global Identification of Co-Translational Interaction Networks by Selective Ribosome Profiling

In recent years, it has become evident that ribosomes not only decode our mRNA but also guide the emergence of the polypeptide chain into the crowded cellular environment. Ribosomes provide the platform for spatially and kinetically controlled binding of membrane-targeting factors, modifying enzymes, and folding chaperones. Even the assembly into high-order oligomeric complexes, as well as protein-protein network formation steps, were recently discovered to be coordinated with synthesis.
Here, we describe Selective Ribosome Profiling, a method developed to capture co-translational interactions in vivo. We will detail the various affinity purification steps required for capturing ribosome-nascent-chain complexes together with co-translational interactors, as well as the mRNA extraction, size exclusion, reverse transcription, deep-sequencing, and big-data analysis steps, required to decipher co-translational interactions in near-codon resolution.

Co-translational interactions play a crucial role in nascent-chain modifications, targeting, folding, and assembly pathways. Here, we describe Selective Ribosome Profiling, a method for in vivo, direct analysis of these interactions in the model eukaryote Saccharomyces cerevisiae.

Identificazione globale delle reti di interazione co-traslazionale mediante profilazione selettiva dei ribosomi

In recent years, it has become evident that ribosomes not only decode our mRNA but also guide the emergence of the polypeptide chain into the crowded ...

Utilizzo di Grafix per la rilevazione di interattori transitori di sottocomplessi di saccharomyces cerevisiae spliceosomi

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