title: Rpb4 subunit functions mainly in mRNA synthesis by RNA polymerase II.
abstract: RNA polymerase II (Pol II) is the central enzyme that carries out eukaryotic mRNA transcription and consists of a 10-subunit catalytic core and a subcomplex of subunits Rpb4 and Rpb7 (Rpb4/7). Rpb4/7 has been proposed to dissociate from Pol II, enter the cytoplasm, and function there in mRNA translation and degradation. Here we provide evidence that Rpb4 mainly functions in nuclear mRNA synthesis by Pol II, as well as evidence arguing against an important cytoplasmic role in mRNA degradation. We used metabolic RNA labeling and comparative Dynamic Transcriptome Analysis to show that Rpb4 deletion in Saccharomyces cerevisiae causes a drastic defect in mRNA synthesis that is compensated by down-regulation of mRNA degradation, resulting in mRNA level buffering. Deletion of Rpb4 can be rescued by covalent fusion of Rpb4 to the Pol II core subunit Rpb2, which largely restores mRNA synthesis and degradation defects caused by Rpb4 deletion. Thus, Rpb4 is a bona fide Pol II core subunit that functions mainly in mRNA synthesis.
authors.affiliation: From the Gene Center Munich and Department of Biochemistry, Center for Integrated Protein Science (CIPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schulz
authors.affiliation: From the Gene Center Munich and Department of Biochemistry, Center for Integrated Protein Science (CIPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich and.
authors.forename: Nicole
authors.initials: N
authors.lastname: Pirkl
authors.affiliation: From the Gene Center Munich and Department of Biochemistry, Center for Integrated Protein Science (CIPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich and.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Lehmann
authors.affiliation: From the Gene Center Munich and Department of Biochemistry, Center for Integrated Protein Science (CIPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich and the Department of Molecular Biology, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany pcramer@mpibpc.mpg.de.
authors.forename: Patrick
authors.initials: P
authors.lastname: Cramer
mesh_terms: D017353:Gene Deletion; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability / Q000502:physiology*; D012331:RNA, Fungal / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D012319:RNA Polymerase II; C423309:RPB4 protein, S cerevisiae; C470553:RPB7 protein, S cerevisiae
keywords: RNA Metabolism; RNA Polymerase II; RNA Turnover; Transcription; mRNA Decay; mRNA Degradation