A novel type of silencing factor, Clr2, is necessary for transcriptional silencing at various chromosomal locations in the fission yeast Schizosaccharomyces pombe.
The mating-type region of the fission yeast Schizosaccharomyces pombe comprises three loci: mat1, mat2-P and mat3-M. mat1 is expressed and determines the mating type of the cell. mat2-P and mat3-M are two storage cassettes located in a 17 kb heterochromatic region with features identical to those of mammalian heterochromatin. Mutations in the swi6+, clr1+, clr2+, clr3+, clr4+ and clr6+ genes were obtained in screens for factors necessary for silencing the mat2-P-mat3-M region. swi6+ encodes a chromodomain protein, clr3+ and clr6+ histone deacetylases, and clr4+ a histone methyltransferase. Here, we describe the cloning and characterization of clr2+. The clr2+ gene encodes a 62 kDa protein with no obvious sequence homologs. Deletion of clr2+ not only affects transcriptional repression in the mating-type region, but also centromeric silencing and silencing of a PolII-transcribed gene inserted in the rDNA repeats. Using chromatin immunoprecipitation, we show that Clr2 is necessary for histone hypoacetylation in the mating-type region, suggesting that Clr2 acts upstream of histone deacetylases to promote transcriptional silencing.
Bjerling
Pernilla
P
Department of Biosciences, Karolinska Institutet, Sodertorn University College, 141 89 Huddinge, Sweden. Pernilla.Bjerling@imbim.uu.se
Ekwall
Karl
K
Egel
Richard
R
Thon
Geneviève
G
D000107:Acetylation; D015825:Chromosomes, Fungal; D003001:Cloning, Molecular; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D006657:Histones / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics* / Q000502:physiology*; D017384:Sequence Deletion; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology*; D014158:Transcription, Genetic
C488801:Clr2 protein, S pombe; D006657:Histones; D012097:Repressor Proteins; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors