Identification of a member of a DNA-dependent ATPase family that causes interference with silencing.
DNA in eukaryotic cells is packed in tandem repeats of nucleosomes or higher-order chromatin structures, which present obstacles to many cellular processes that require protein-DNA interactions, such as transcription, DNA repair, and recombination. To find proteins that are involved in increasing the accessibility of specific DNA regions in yeast, we used a genetic approach that exploited transcriptional silencing normally occurring at HML and HMR loci. The silencing is mediated by cis-acting silencer elements and is thought to require the formation of a special chromatin structure that prevents accessibility to the silenced DNA. A previously uncharacterized gene, termed DIS1, was isolated from a screen for genes that interfere with silencing when overexpressed. DIS1 encodes a protein with conserved motifs that are present in a family of DNA-dependent ATPases, the SWI2/SNF2-like proteins. Overproduction of N-terminal half of DIS1 protein interfered specifically with ectopic silencing used in the screen as well as HMR E silencing. Two-hybrid studies revealed a specific interaction between the N terminus of DIS1 and the C-terminal half of SIR4, a protein essential for silencing. Cells with a dis1 knockout mutation had significantly lower mating-type switching rate. These results suggest that DIS1 may contribute to making the silenced DNA template at HM loci more accessible during the mating-type switching process.
Zhang
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Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA. zxz1@cgl.ucsf.edu
Buchman
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AR
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D004265:DNA Helicases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D014157:Transcription Factors; D000251:Adenosine Triphosphatases; C499333:SNF2 protein, S cerevisiae; C506745:ULS1 protein, S cerevisiae; D004265:DNA Helicases