title: Nuclear actin and myosin I are required for RNA polymerase I transcription.
abstract: The presence of actin and nuclear myosin I (NMI) in the nucleus suggests a role for these motor proteins in nuclear functions. We have investigated the role of actin and nuclear myosin I (NMI) in the transcription of ribosomal RNA genes (rDNA). Both proteins are associated with rDNA and are required for RNA polymerase I (Pol I) transcription. Microinjection of antibodies against actin or NMI, as well as short interfering RNA-mediated depletion of NMI, decreased Pol I transcription in vivo, whereas overexpression of NMI augmented pre-rRNA synthesis. In vitro, recombinant NMI activated Pol I transcription, and antibodies to NMI or actin inhibited Pol I transcription both on naked DNA and pre-assembled chromatin templates. Whereas actin associated with Pol I, NMI bound to Pol I through the transcription-initiation factor TIF-IA. The association with Pol I requires phosphorylation of TIF-IA at Ser 649 by RSK kinase, indicating a role for NMI in the growth-dependent regulation of rRNA synthesis.
authors.affiliation: Department of Cell Ultrastructure and Molecular Biology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague 14220, Czech Republic.
authors.forename: Vlada V
authors.initials: VV
authors.lastname: Philimonenko
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: Sebastian
authors.initials: S
authors.lastname: Iben
authors.forename: Hana
authors.initials: H
authors.lastname: Dingová
authors.forename: Katarína
authors.initials: K
authors.lastname: Kyselá
authors.forename: Michal
authors.initials: M
authors.lastname: Kahle
authors.forename: Hanswalter
authors.initials: H
authors.lastname: Zentgraf
authors.forename: Wilma A
authors.initials: WA
authors.lastname: Hofmann
authors.forename: Primal
authors.initials: P
authors.lastname: de Lanerolle
authors.forename: Pavel
authors.initials: P
authors.lastname: Hozák
authors.forename: Ingrid
authors.initials: I
authors.lastname: Grummt
mesh_terms: D000199:Actins / Q000378:metabolism*; D000906:Antibodies / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000235:genetics; D006801:Humans; D024461:Myosin Type I / Q000378:metabolism*; D035463:Pol1 Transcription Initiation Complex Proteins; D011485:Protein Binding / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012318:RNA Polymerase I / Q000096:biosynthesis* / Q000235:genetics; D012335:RNA, Ribosomal / Q000096:biosynthesis* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases; D012694:Serine / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D000199:Actins; D000906:Antibodies; D004275:DNA, Ribosomal; D035463:Pol1 Transcription Initiation Complex Proteins; D012335:RNA, Ribosomal; C428423:RRN3 protein, human; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D012694:Serine; D011494:Protein Kinases; D019893:Ribosomal Protein S6 Kinases; D012318:RNA Polymerase I; D024461:Myosin Type I