Rsp5 WW Domains Interact Directly with the Carboxyl-terminal Domain of RNA Polymerase II

Abstract

RSP5 is an essential gene inSaccharomyces cerevisiae and was recently shown to form a physical and functional complex with RNA polymerase II (RNA pol II). The amino-terminal half of Rsp5 consists of four domains: a C2 domain, which binds membrane phospholipids; and three WW domains, which are protein interaction modules that bind proline-rich ligands. The carboxyl-terminal half of Rsp5 contains a HECT (homologous to E6-AP carboxyl terminus) domain that catalytically ligates ubiquitin to proteins and functionally classifies Rsp5 as an E3 ubiquitin-protein ligase. The C2 and WW domains are presumed to act as membrane localization and substrate recognition modules, respectively. We report that the second (and possibly third) Rsp5 WW domain mediates binding to the carboxyl-terminal domain (CTD) of the RNA pol II large subunit. The CTD comprises a heptamer (YSPTSPS) repeated 26 times and a PXY core that is critical for interaction with a specific group of WW domains. An analysis of synthetic peptides revealed a minimal CTD sequence that is sufficient to bind to the second Rsp5 WW domain (Rsp5 WW2) in vitro and in yeast two-hybrid assays. Furthermore, we found that specific “imperfect” CTD repeats can form a complex with Rsp5 WW2. In addition, we have shown that phosphorylation of this minimal CTD sequence on serine, threonine and tyrosine residues acts as a negative regulator of the Rsp5 WW2-CTD interaction. In view of the recent data pertaining to phosphorylation-driven interactions between the RNA pol II CTD and the WW domain of Ess1/Pin1, we suggest that CTD dephosphorylation may be a prerequisite for targeted RNA pol II degradation. RSP5 is an essential gene inSaccharomyces cerevisiae and was recently shown to form a physical and functional complex with RNA polymerase II (RNA pol II). The amino-terminal half of Rsp5 consists of four domains: a C2 domain, which binds membrane phospholipids; and three WW domains, which are protein interaction modules that bind proline-rich ligands. The carboxyl-terminal half of Rsp5 contains a HECT (homologous to E6-AP carboxyl terminus) domain that catalytically ligates ubiquitin to proteins and functionally classifies Rsp5 as an E3 ubiquitin-protein ligase. The C2 and WW domains are presumed to act as membrane localization and substrate recognition modules, respectively. We report that the second (and possibly third) Rsp5 WW domain mediates binding to the carboxyl-terminal domain (CTD) of the RNA pol II large subunit. The CTD comprises a heptamer (YSPTSPS) repeated 26 times and a PXY core that is critical for interaction with a specific group of WW domains. An analysis of synthetic peptides revealed a minimal CTD sequence that is sufficient to bind to the second Rsp5 WW domain (Rsp5 WW2) in vitro and in yeast two-hybrid assays. Furthermore, we found that specific “imperfect” CTD repeats can form a complex with Rsp5 WW2. In addition, we have shown that phosphorylation of this minimal CTD sequence on serine, threonine and tyrosine residues acts as a negative regulator of the Rsp5 WW2-CTD interaction. In view of the recent data pertaining to phosphorylation-driven interactions between the RNA pol II CTD and the WW domain of Ess1/Pin1, we suggest that CTD dephosphorylation may be a prerequisite for targeted RNA pol II degradation. RNA polymerase II carboxyl-terminal domain glutathioneS-transferase phosphate-buffered saline Yes kinase-associated protein small peptides synthesized on devivatized membranes RSP5 (reversion of Sptphenotype) is an essential gene in the yeastSaccharomyces cerevisiae. The gene was originally isolated in a screen for suppressors of SPT3 mutations (1.Eisenmann D.M. Arndt K.M. Ricupero S.L. Rooney J.W. Winston F. Genes Dev. 1992; 6: 1319-1331Crossref PubMed Scopus (189) Google Scholar).SPT3 is part of the multicomponent protein named SAGA (Spt-Ada-Gcn5acetyltransferase), which has been implicated in at least two facets of RNA pol II1activity. These include the function of the TATA box-binding protein Spt15 and the activity of Gcn5 histone acetyltransferase (1.Eisenmann D.M. Arndt K.M. Ricupero S.L. Rooney J.W. Winston F. Genes Dev. 1992; 6: 1319-1331Crossref PubMed Scopus (189) Google Scholar, 2.Roberts S.M. Winston F. Genetics. 1997; 147: 451-465Crossref PubMed Google Scholar). Moreover, Rsp5 was recently shown to form a physical and functional complex with RNA pol II (3.Huibregtse J.M. Yang J.C. Beaudenon S.L. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 3656-3661Crossref PubMed Scopus (180) Google Scholar, 4.Wang G. Yang J. Huibregtse J.M. Mol. Cell. Biol. 1999; 19: 342-352Crossref PubMed Scopus (146) Google Scholar). In addition to its interaction with RNA pol II, Rsp5 possesses multiple and diverse substrates, suggesting that Rsp5 affects a wide range of cellular processes. For example, RSP5 is known to down-regulate the activity of several plasma membrane-associated proteins, including Fur4 uracil permease, Gap1 amino acid permease, and the integral membrane protein proton ATPase (5.Hein C. Springael J.Y. Volland C. Haguenauer-Tsapis R. Andre B. Mol. Microbiol. 1995; 18: 77-87Crossref PubMed Scopus (297) Google Scholar, 6.Galan J.M. Moreau V. Andre B. Volland C. Haguenauer-Tsapis R. J. Biol. Chem. 1996; 271: 10946-10952Abstract Full Text Full Text PDF PubMed Scopus (264) Google Scholar, 7.de la Fuente N. Maldonado A.M. Portillo F. FEBS Lett. 1997; 411: 308-312Crossref PubMed Scopus (34) Google Scholar, 8.Springael J.Y. Andre B. Mol. Biol. Cell. 1998; 9: 1253-1263Crossref PubMed Scopus (186) Google Scholar). Rsp5 was recently proposed to be a component of a complex regulating an early stage of endocytosis (9.Wendland B. Emr S.D. Riezman H. Curr. Opin. Cell Biol. 1998; 10: 513-522Crossref PubMed Scopus (150) Google Scholar). Mutations in RSP5 have also been shown to regulate stability of a minichromosome (10.Uesono Y. Fujita A. Toh-e A. Kikuchi Y. Gene (Amst.). 1994; 143: 135-138Crossref PubMed Scopus (42) Google Scholar) and the cytoplasmic/mitochondrial distribution of Mod5, an enzyme that modifies tRNA (11.Zoladek T. Tobiasz A. Vaduva G. Boguta M. Martin N.C. Hopper A.K. Genetics. 1997; 145: 595-603Crossref PubMed Google Scholar). In addition, Rsp5-mediated ubiquitination has been implicated in mitochondrial inheritance (12.Fisk H.A. Yaffe M.P. J. Cell Biol. 1999; 145: 1199-1208Crossref PubMed Scopus (158) Google Scholar). The primary structure of Rsp5 reveals a multidomain topology (Fig.1). The amino-terminal half of Rsp5 consists of four domains: a C2 domain, which may bind membrane phospholipids and inositol phosphates in a calcium-regulated manner; and three WW domains (WW1, WW2, and WW3), which are protein interaction modules that bind proline-rich ligands. The carboxyl-terminal half of Rsp5 contains a HECT (homologous to E6-APcarboxyl terminus) domain (13.Huibregtse J.M. Scheffner M. Beaudenon S. Howley P.M. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 2563-2567Crossref PubMed Scopus (695) Google Scholar). The HECT domain encodes an E3 ubiquitin-protein ligase activity, which ligates ubiquitin in the process of targeted protein degradation (14.Ciechanover A. EMBO J. 1998; 17: 7151-7160Crossref PubMed Scopus (1180) Google Scholar). Presumably, the C2 and WW domains act as membrane localization and substrate recognition modules for Rsp5, respectively (3.Huibregtse J.M. Yang J.C. Beaudenon S.L. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 3656-3661Crossref PubMed Scopus (180) Google Scholar, 15.Plant P.J. Yeger H. Staub O. Howard P. Rotin D. J. Biol. Chem. 1997; 272: 32329-32336Abstract Full Text Full Text PDF PubMed Scopus (158) Google Scholar, 16.Springael J.Y. De Craene J.O. Andre B. Biochem. Biophys. Res. Commun. 1999; 257: 561-566Crossref PubMed Scopus (47) Google Scholar). The WW domain is a small protein interaction module composed of 40 amino acids that fold into a three-stranded, anti-parallel β-sheet, which constitutes a hydrophobic pocket for binding proline-rich ligands (17.Bork P. Sudol M. Trends Biochem. Sci. 1994; 19: 531-533Abstract Full Text PDF PubMed Scopus (346) Google Scholar, 18.Chen H.I. Sudol M. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 7819-7823Crossref PubMed Scopus (485) Google Scholar, 19.Macias M.J. Hyvonen M. Baraldi E. Schultz J. Sudol M. Saraste M. Oschkinat H. Nature. 1996; 382: 646-649Crossref PubMed Scopus (360) Google Scholar). The WW domain is named after two conserved tryptophan residues spaced 20–22 amino acids apart (20.Sudol M. Prog. Biophys. Mol. Biol. 1996; 65: PubMed Scopus Google Scholar). on binding the WW domains can be into two and three M.P. Sudol M. J. PubMed Scopus Google Scholar). WW domains, the and WW domains, bind proteins with H.I. Sudol M. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 7819-7823Crossref PubMed Scopus (485) Google S. H. Sudol M. Biol. Chem. 1999; PubMed Scopus Google Scholar). the of the binding to WW domains, H.I. A. H. E. S. J.W. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar) and 1998; PubMed Scopus Google Scholar, G. J.M. D.M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar) have shown that in a this can be specific amino acids as and The for WW domain binding the PXY core and II WW domains, WW domains of and proteins, bind to N. H. G. F. T. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, P. EMBO J. 1997; PubMed Scopus Google Scholar). the three of WW domains, and bind proline-rich M.P. Sudol M. J. PubMed Scopus Google A. M. S. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar, M. S. Y. M. Mol. 1999; PubMed Scopus Google Scholar). WW domains shown to with threonine the binding of WW domains to ligands was shown to be P.J. M. 1999; PubMed Scopus Google Scholar, J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). The RNA pol II large is the component of the for of of Biophys. 1995; PubMed Scopus Google Scholar). The yeast of RNA pol II in its a heptamer sequence (YSPTSPS) repeated times and four times An of the CTD sequence revealed a PXY core the repeated heptamer S.L. G. Huibregtse J.M. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar). The CTD has for phosphorylation CTD and and dephosphorylation CTD Biophys. 1995; PubMed Scopus Google Scholar). In addition to a known function of the CTD is the to M. H. P. Genes Dev. 1998; PubMed Scopus Google Scholar). is on the and functional of the WW domain as a protein interaction and module M. 1998; 17: PubMed Scopus Google Scholar). the of cerevisiae we that we protein ligands binding to yeast WW domains on of binding we to a interaction between Rsp5 WW domains and the RNA pol II CTD the PXY was found to be a minimal core that with WW domains 1998; PubMed Scopus Google Scholar, H.I. A. H. E. S. J.W. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, G. J.M. D.M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). for ligands was to and to the for yeast WW domain, including the three Rsp5 WW domains. the binding the yeast data was for proteins the in an to ligands for and of WW and with the Rsp5 WW domains revealed a interaction with RNA pol II, and this interaction was We report that Rsp5 (and possibly mediates binding to the CTD of RNA pol We to a minimal CTD that is sufficient to bind to Rsp5 in vitro and in the yeast two-hybrid In addition, we have shown that phosphorylation of the minimal CTD sequence on serine, and tyrosine residues may act as a negative regulator of the Rsp5 WW2-CTD interaction. In view of the recent data pertaining to phosphorylation-driven interactions between the RNA pol II CTD and the J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google we suggest that CTD dephosphorylation may be a prerequisite for targeted RNA pol II degradation. The Rsp5 WW domains and the CTD of RNA polymerase II and into to The and of are as enzyme and The and and H.I. A. H. E. S. J.W. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, N. H. G. F. T. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, Sudol M. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). The with enzyme and for into the of the domains in to the the WW domains polymerase the and of the RNA pol II the proteins isolated as with and of E. S.L. J. Cell Biol. 1997; PubMed Scopus Google Scholar). a CTD with and a CTD with M. R. M. O. S.L. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). We two to an in of protein interactions contains the domain and a for proteins of the domain and a gene of The contains the domain and also contains for We the multiple of and that we to the the second Rsp5 WW domain into and the the minimal CTD into The named and For we two synthesized The two at the of the to into and the for of and named of the proteins was after to at and the for an at The was and the was in and and The was into and at to of the of the protein was the The in the of for with and with and in of and The for and proteins on a the for at the to the of the the was with for and the was The the Rsp5 WW domains have a and protein phosphorylation between and the WW The proteins with and with and and and The for with of of protein and of The in a with and and with with in The proteins on as with WW domain of Rsp5, we for binding the of the H. S. Sudol M. Biol. Chem. 1997; PubMed Scopus Google Scholar). we two and the amino acid and the of the consists of three of Rsp5 WW domain in of for to bind the WW domains and the protein The of and for The for Rsp5 WW domain to the yeast data for proteins the binding The and specific data in II, the to and to The PXY the the J. Mol. Biol. PubMed Scopus Google data for yeast proteins the data pol of and protein data data protein enzyme pol II, in ubiquitination data of RNA pol in endocytosis regulator for for for data and regulator of complex protein protein protein data ligase of complex of complex for of protein acid at the the For the data PXY was with the to and to The data and with the for and For data the of including an and the function of the are in the respectively. For the specific data sequence for Rsp5 WW domains was to the yeast data The and the proteins, proteins For and we the and protein in a at the the For the data PXY was with the to and to The data and with the for and For data the of including an and the function of the are in the respectively. For the specific data sequence for Rsp5 WW domains was to the yeast data The and the proteins, proteins For and we the and protein yeast in The with and in protein and with The into An of was and the was for and on for two the at for at The to and the of yeast Rsp5 WW2, in binding and for a of at was with binding and the binding proteins in and the for proteins binding to WW domains. The on and The membranes in and and for at with WW domains in the binding the at least three times with and to The proteins on the to the was for at least at with The with WW domains CTD and as peptides synthesized on membranes as R. R. Scopus Google Scholar, B. B. R. Lett. Scopus Google Scholar). membrane was with and in The membranes for at for at and three times for at H.I. A. H. E. S. J.W. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, H. S. Sudol M. Biol. Chem. 1997; PubMed Scopus Google Scholar). The two yeast and into S. O. Nature. PubMed Scopus Google Scholar). For on and for on the was and with and on and was on and and for its to We to ligands for WW domain of Rsp5 and the we the sequence for ligands to WW domain and proteins in the yeast The of for Rsp5 WW domain are in The sequence for Rsp5 WW domain is as WW2, and The binding for WW domain is a the three Rsp5 WW domains to two and and to the sequence the These two the a with the 1998; PubMed Scopus Google Scholar, H.I. A. H. E. S. J.W. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, G. J.M. D.M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google of peptides Rsp5 WW three Rsp5 WW domains (WW1, WW2, and to screen two for The Rsp5 WW2, and are in respectively. The the and The reveals the sequence The the of binding of the to the WW domain, as and For WW domain, a sequence of was and is in the of in a The three Rsp5 WW domains (WW1, WW2, and to screen two for The Rsp5 WW2, and are in respectively. The the and The reveals the sequence The the of binding of the to the WW domain, as and For WW domain, a sequence of was and is in the of of the yeast data the the ligands in The proteins are in diverse as and amino acid The also the proteins of We the specific data in of II with a data of the yeast for PXY and for and in The ligands in in data in The that are data screen for in II we to binding proteins yeast proteins of Rsp5 WW domains, we a protein of in with RSP5 and In addition, two protein in with Rsp5 on the of the proteins and data a interaction between Rsp5 and RNA pol II G. Yang J. Huibregtse J.M. Mol. Cell. Biol. 1999; 19: 342-352Crossref PubMed Scopus (146) Google we that the protein was RNA pol We the and with specific for the large of RNA pol II and that the which at was RNA pol II is RNA polymerase was of and with that the CTD of RNA polymerase The the the binding the protein interaction between WW domains of Rsp5 and the yeast RNA pol II we proteins of yeast RNA pol II found in and and a found in to and with Rsp5 WW and the that was to bind WW domains H.I. Sudol M. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 7819-7823Crossref PubMed Scopus (485) Google H. S. Sudol M. Biol. Chem. 1997; PubMed Scopus Google Scholar). contains a and was shown to bind to N. H. G. F. T. Sudol M. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). The CTD contains 26 heptamer repeats of the yeast We that Rsp5 WW domain to and and bind to the Rsp5 WW domain to the yeast CTD we a of Rsp5 WW domains and with the yeast we that WW domain the to bind the CTD and found that Rsp5 to the yeast CTD Rsp5 was to RNA pol II yeast and to with the we on the of the specific binding in the The amino acid residues of the CTD are as In an to the minimal that with Rsp5 WW2, we synthesized CTD peptides on membranes and the of a the amino carboxyl the with on we have as the CTD that binds Rsp5 WW2. a CTD was also to with Rsp5 WW2. membranes with the of peptides and with and proteins, binding was the amino acid residues in the interaction between the minimal CTD and Rsp5 WW2, we the minimal CTD binding with the peptides are synthesized the carboxyl was to the to an and for to the tyrosine tyrosine and with binding and that the and threonine and in binding was threonine was with and The on binding was was with The data that the amino acid residues for an interaction between the minimal CTD binding and Rsp5 These data the minimal PXY core shown in and revealed the of amino acid we CTD phosphorylation binding to Rsp5 WW2. We synthesized peptides of the CTD on membranes serine, The Rsp5 WW domains and for the In this we that Rsp5 the minimal CTD at specific of the CTD binding of Rsp5 in of an amino-terminal the minimal CTD binding is minimal on of threonine and the interaction with the peptides and and and phosphorylation of tyrosine tyrosine threonine and binding and of and CTD repeats on was and with the and and CTD repeats synthesized on membranes as These are and serine, tyrosine was with a amino acid the membrane was a to the of We repeated the with CTD peptides at multiple including phosphorylation in residues the and the phosphorylation in the We also of multiple CTD of the CTD was have shown that phosphorylation can regulate binding between the CTD and Rsp5 II phosphorylation binding Rsp5 may have a for binding the CTD on Rsp5 WW2, and II, and the CTD contains repeats as we to serine, and tyrosine residues on repeats to the of Rsp5 to bind of the CTD we a binding Rsp5 WW2, for a CTD with an at for a minimal CTD We that repeats may have for binding Rsp5 We synthesized CTD in and on membranes and with Rsp5 WW2. We that phosphorylation of repeats a negative on binding to Rsp5 with the repeats For the we that amino acid can binding at of the minimal CTD which also to of the PXY core binding For example, in two repeats in which an was binding of Rsp5 for the and a of with binding with the with in and was and with and respectively the interaction of Rsp5 with a CTD at threonine was as with the binding of Rsp5 to an with and In CTD repeats interactions with Rsp5 with the Rsp5 and the minimal RNA pol II CTD into as with the domain and the domain to be for protein interaction in the yeast two-hybrid pol II on and and to a was to we that vitro binding we for Rsp5 and the minimal CTD can also in yeast We have the binding between Rsp5 WW domains and the CTD of RNA pol The second WW domain of Rsp5 was to the RNA pol II yeast and bind to Furthermore, we have the minimal of the CTD peptides that can the Rsp5 WW2-CTD interaction in vitro and in yeast the of of the minimal CTD the CTD repeats as for binding Rsp5 WW domains. In addition, we that the phosphorylation of the CTD residues has an negative on binding to Rsp5 WW2. RNA pol II and proteins have been shown to with Rsp5 and (3.Huibregtse J.M. Yang J.C. Beaudenon S.L. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 3656-3661Crossref PubMed Scopus (180) Google Scholar, 4.Wang G. Yang J. Huibregtse J.M. Mol. Cell. Biol. 1999; 19: 342-352Crossref PubMed Scopus (146) Google Scholar, S.L. G. Huibregtse J.M. Mol. Cell. Biol. 1999; 19: PubMed Scopus Google Scholar, H. D. Toh-e A. Kikuchi Y. Gene (Amst.). 1998; PubMed Scopus Google Scholar, H. T. Y. Kikuchi Y. Mol. Cell. Biol. 1996; PubMed Google Scholar). the membrane we that peptides the times CTD peptides a PXY Rsp5 was in yeast RNA pol II was the protein that was We a protein between and the of that of RNA pol II and are in be for is that the of CTD repeats may a that Rsp5 WW domains into a large and complex with the RNA pol II The of the PXY with the structure of the CTD for complex The analysis of CTD in an a minimal CTD that binds Rsp5 the of the CTD with revealed a that to Rsp5 as as the minimal CTD the and peptides in the negative for is to is that the of residues the PXY core in this into a to the minimal CTD and the PXY core for is that CTD repeats can a of amino acids and specific amino acid residues of the are A. J. Mol. Biol. PubMed Scopus Google Scholar). we have an CTD sequence as the minimal for binding Rsp5 in we are the structure of Rsp5 in the CTD as as to at the complex of Rsp5 with the CTD was two The yeast two-hybrid the of Rsp5 to form a complex with the of CTD in In addition, we an structure of Rsp5 in complex with the CTD structure the in the complex of the WW domain with the M.J. Hyvonen M. Baraldi E. Schultz J. Sudol M. Saraste M. Oschkinat H. Nature. 1996; 382: 646-649Crossref PubMed Scopus (360) Google Scholar). A. M. and M. J. has the of RNA pol II CTD phosphorylation with activity H. H. O. D. Genes Dev. 1999; PubMed Scopus Google Scholar). In RNA pol II are in the with RNA pol II in at Curr. Opin. Cell Biol. 1999; PubMed Scopus Google Scholar). The RNA pol II with a CTD the and to Biophys. 1995; PubMed Scopus Google Scholar, D. J.W. Curr. Opin. Cell Biol. 1999; PubMed Scopus Google Scholar). CTD phosphorylation and dephosphorylation can its and the proteins that with the CTD and the RNA pol II M. H. P. Genes Dev. 1998; PubMed Scopus Google Scholar). the stage of the CTD with proteins in CTD the proteins that with the CTD are in O. F. C. B. Biochem. Cell Biol. 1999; PubMed Scopus Google Scholar, D. Curr. Opin. Cell Biol. 1999; PubMed Scopus Google Scholar). of the of data is that the CTD may an interaction with Rsp5 ubiquitin to RNA pol II for degradation in the on we two CTD may a dephosphorylation of the Rsp5 WW domains to form a complex with the CTD at CTD may specific CTD possibly and the of Rsp5 WW domains to form a complex with the The and is several that a form of RNA pol II with the CTD is targeted ubiquitin R. S.L. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar, A. Proc. Natl. Acad. Sci. U. S. A. 1999; PubMed Scopus Google Scholar, B. J. S.L. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus (189) Google Scholar). In several have shown that which contains an and a WW domain, is to with the RNA pol II CTD and to regulate activity several which include the of the and of RNA pol J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar, A. S. M. J. Cell Sci. 1999; Google J. B. A. H. G. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). A. H. M. E. P. T. and J. P. for Y. C. B. G. R. M. M. E. J. and S. D. for the CTD its WW domain, an The CTD of RNA pol II has an to form with two WW proteins, Rsp5 and which and RNA pol II in of functional of in yeast Rsp5 with specific mutations that the stability of RNA pol II of We for to the carboxyl-terminal domain of RNA pol II, for the and in of yeast and for in of yeast We also on the D. A. S. J. B. A. M. R. and E.