Bjerling Pernilla, Ekwall Karl, Egel Richard, Thon Geneviève
Department of Biosciences, Karolinska Institutet, Sodertorn University College, 141 89 Huddinge, Sweden.
Nucleic Acids Res. 2004 Aug 18;32(15):4421-8. doi: 10.1093/nar/gkh780. Print 2004.
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.
mat1、mat2-P和mat3-M。mat1表达并决定细胞的交配型。mat2-P和mat3-M是两个存储盒，位于一个17 kb的异染色质区域，其特征与哺乳动物异染色质相同。在筛选沉默mat2-P-mat3-M区域所需因子的过程中，获得了swi6+、clr1+、clr2+、clr3+、clr4+和clr6+基因的突变。swi6+编码一种色域蛋白，clr3+和clr6+编码组蛋白脱乙酰酶，clr4+编码一种组蛋白甲基转移酶。在这里，我们描述clr2+的克隆和特征。clr2+基因编码一种62 kDa的蛋白质，没有明显的序列同源物。clr2+的缺失不仅影响交配型区域的转录抑制，还影响着丝粒沉默以及插入rDNA重复序列中的PolII转录基因的沉默。使用染色质免疫沉淀，我们表明Clr2是交配型区域组蛋白低乙酰化所必需的，这表明Clr2在组蛋白脱乙酰酶上游起作用以促进转录沉默。
