title: Transcription regulation of the rRNA gene by a multifunctional nucleolar protein, B23/nucleophosmin, through its histone chaperone activity.
abstract: It is well established that the transcription rate of the rRNA gene is closely associated with profound alterations in the cell growth rate. Regulation of rRNA gene transcription is likely to be dependent on the dynamic conversion of the chromatin structure. Previously, we identified B23/nucleophosmin, a multifunctional nucleolar phosphoprotein, as a component of template activating factor III that remodels the chromatin-like structure of the adenovirus genome complexed with viral basic proteins. It has also been shown that B23 has histone chaperone activity. Here, we examined the effect of B23 on rRNA gene transcription. B23 was found to be associated with the rRNA gene chromatin. Small-interfering-RNA-mediated down-regulation of the B23 expression level resulted in reduction of the transcription rate of the rRNA gene. We constructed a B23 mutant termed B23DeltaC, which lacks the domain essential for the histone chaperone activity and inhibited the histone binding activity of B23 in a dominant-negative manner. Expression of B23DeltaC decreased rRNA gene transcription and the rate of cell proliferation. These results suggest that B23 is involved in the transcription regulation of the rRNA gene as a nucleolar histone chaperone.
authors.affiliation: Department of Infection Biology, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Murano
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Okuwaki
authors.forename: Miharu
authors.initials: M
authors.lastname: Hisaoka
authors.forename: Kyosuke
authors.initials: K
authors.lastname: Nagata
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D049109:Cell Proliferation; D042002:Chromatin Assembly and Disassembly; D018076:DNA, Complementary / Q000235:genetics; D017353:Gene Deletion; D016158:Genes, p53; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000090243:Nucleophosmin; D012335:RNA, Ribosomal / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D006657:Histones; D018832:Molecular Chaperones; C000716967:NPM1 protein, human; C000715570:Npm1 protein, mouse; D009687:Nuclear Proteins; D012335:RNA, Ribosomal; D034741:RNA, Small Interfering; D000090243:Nucleophosmin