title: Multiple protein-protein interactions by RNA polymerase I-associated factor PAF49 and role of PAF49 in rRNA transcription.
abstract: We previously demonstrated the critical role of RNA polymerase I (Pol I)-associated factor PAF53 in mammalian rRNA transcription. Here, we report the isolation and characterization of another Pol I-associated factor, PAF49. Mouse PAF49 shows striking homology to the human nucleolar protein ASE-1, so that they are considered orthologues. PAF49 and PAF53 were copurified with a subpopulation of Pol I during purification from cell extracts. Physical association of PAF49 with Pol I was confirmed by a coimmunoprecipitation assay. PAF49 was shown to interact with PAF53 through its N-terminal segment. This region of PAF49 also served as the target for TAF(I)48, the 48-kDa subunit of selectivity factor SL1. Concomitant with this interaction, the other components of SL1 also coimmunoprecipitated with PAF49. Specific transcription from the mouse rRNA promoter in vitro was severely impaired by anti-PAF49 antibody, which was overcome by addition of recombinant PAF49 protein. Moreover, overexpression of a deletion mutant of PAF49 significantly reduced pre-rRNA synthesis in vivo. Immunolocalization analysis revealed that PAF49 accumulated in the nucleolus of growing cells but dispersed to nucleoplasm in growth-arrested cells. These results strongly suggest that PAF49/ASE-1 plays an important role in rRNA transcription.
authors.affiliation: Department of Biochemistry, Saitama Medical School, Iruma-gun, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Mika
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Hanada
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Nogi
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Matsuyama
authors.forename: Masami
authors.initials: M
authors.lastname: Muramatsu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism; D012318:RNA Polymerase I / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D014158:Transcription, Genetic
chemical_list: D002352:Carrier Proteins; D009687:Nuclear Proteins; C488429:PAF49 protein, mouse; C099638:POLR1E protein, human; C484388:Paf53 protein, mouse; D035463:Pol1 Transcription Initiation Complex Proteins; D012335:RNA, Ribosomal; C091131:TAF1A protein, human; D014157:Transcription Factors; D012318:RNA Polymerase I