title: The SCFDia2 ubiquitin E3 ligase ubiquitylates Sir4 and functions in transcriptional silencing.
abstract: In budding yeast, transcriptional silencing, which is important to regulate gene expression and maintain genome integrity, requires silent information regulator (Sir) proteins. In addition, Rtt106, a histone chaperone involved in nucleosome assembly, functions in transcriptional silencing. However, how transcriptional silencing is regulated during mitotic cell division is not well understood. We show that cells lacking Dia2, a component of the SCF(Dia2) E3 ubiquitin ligase involved in DNA replication, display defects in silencing at the telomere and HMR locus and that the F-box and C-terminal regions of Dia2, two regions important for Dia2's ubiquitylation activity, are required for proper transcriptional silencing at these loci. In addition, we show that Sir proteins are mislocalized in dia2Δ mutant cells. Mutations in Dia2 and Rtt106 result in a synergistic loss of silencing at the HMR locus and significant elevation of Sir4 proteins at the HMR locus, suggesting that silencing defects in dia2Δ mutant cells are due, at least in part, to the altered levels of Sir4 at silent chromatin. Supporting this idea, we show that SCF(Dia2) ubiquitylates Sir4 in vitro and in vivo. Furthermore, Sir4 binding to silent chromatin is dynamically regulated during the cell cycle, and this regulation is lost in dia2Δ mutant cells. These results demonstrate that the SCF(Dia2) complex is involved in transcriptional silencing, ubiquitylates Sir4, and regulates transcriptional silencing during the cell cycle.
authors: Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First Street SW, MN 55905, USA.
authors: Rebecca J
authors: RJ
authors: Burgess
authors: Hui
authors: H
authors: Zhou
authors: Junhong
authors: J
authors: Han
authors: Qing
authors: Q
authors: Li
authors: Zhiguo
authors: Z
authors: Zhang
mesh_terms: D004261:DNA Replication / Q000235:genetics*; D044783:F-Box Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D006570:Heterochromatin / Q000235:genetics; D008938:Mitosis / Q000235:genetics; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009707:Nucleosomes / Q000235:genetics; D016196:S Phase / Q000235:genetics; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D016615:Telomere / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D054875:Ubiquitination / Q000235:genetics*
chemical_list: C495983:Dia2 protein, S cerevisiae; D044783:F-Box Proteins; D006570:Heterochromatin; D018832:Molecular Chaperones; D009707:Nucleosomes; C505157:Rtt106 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D044843:SKP Cullin F-Box Protein Ligases