title: Rsp5 WW domains interact directly with the carboxyl-terminal domain of RNA polymerase II.
abstract: RSP5 is an essential gene in Saccharomyces 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, New York University/Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: A
authors.initials: A
authors.lastname: Chang
authors.forename: S
authors.initials: S
authors.lastname: Cheang
authors.forename: X
authors.initials: X
authors.lastname: Espanel
authors.forename: M
authors.initials: M
authors.lastname: Sudol
mesh_terms: D020650:Combinatorial Chemistry Techniques; D016208:Databases, Factual; D056827:Endosomal Sorting Complexes Required for Transport; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D019151:Peptide Library; D010766:Phosphorylation; D011485:Protein Binding; D012319:RNA Polymerase II / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D005656:Fungal Proteins; D010446:Peptide Fragments; D019151:Peptide Library; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D012319:RNA Polymerase II; C469287:RSP5 protein, S cerevisiae