title: The mitotic Clb cyclins are required to alleviate HIR-mediated repression of the yeast histone genes at the G1/S transition.
abstract: The histone genes are an important group of cell cycle regulated genes whose transcription is activated during the G1/S transition and repressed in early G1, late S, and G2/M. The HIR complex, comprised of Hir1, Hir2, Hir3 and Hpc2, regulates three of the four histone gene loci. While relief of repression at the G1/S boundary involves the HIR complex, as well as other cofactors, the mechanism by which this derepression occurs remains unknown. To better understand how transcriptional repression contributes to periodic expression in the cell cycle, we sought to identify the cell cycle signals required to alleviate HIR-mediated repression of the histone genes. By measuring histone gene transcription in strains with various combinations of clb mutations, we found that the mitotic Clb1/Clb2 cyclins are required to alleviate Hir-mediated repression during the G1/S transition and that Clb2 physically interacts with the HIR complex. While the HIR complex regulates histone gene transcription in combination with two other histone H3/H4 chaperones, Asf1 and Rtt106, our data demonstrate that the mitotic Clb cyclins are necessary to specifically alleviate the repressive action of the HIR complex itself in order to allow proper expression of the histone genes in late G1/early S phase.
authors: Department of Pathology and Laboratory Medicine, University of Kansas Medical School, Kansas City, KS, USA.
authors: Amit Dipak
authors: AD
authors: Amin
authors: Dessislava K
authors: DK
authors: Dimova
authors: Monica E
authors: ME
authors: Ferreira
authors: Nidhi
authors: N
authors: Vishnoi
authors: Leandria C
authors: LC
authors: Hancock
authors: Mary Ann
authors: MA
authors: Osley
authors: Philippe
authors: P
authors: Prochasson
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D019926:Cyclin B / Q000235:genetics* / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D059585:G1 Phase Cell Cycle Checkpoints; D015966:Gene Expression Regulation, Fungal; D006657:Histones / Q000235:genetics* / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000235:genetics; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: C109731:ASF1 protein, S cerevisiae; C080443:CDC4 protein, S cerevisiae; C068264:CLB1 protein, S cerevisiae; C093749:CLB2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D016213:Cyclins; D004268:DNA-Binding Proteins; D044783:F-Box Proteins; C078808:HIR1 protein, S cerevisiae; C078809:HIR2 protein, S cerevisiae; D006657:Histones; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D012097:Repressor Proteins; C505157:Rtt106 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D044767:Ubiquitin-Protein Ligases