Thon G, Klar A J
NCI-Frederick Cancer Research and Development Center, ABL-Basic Research Program, Laboratory of Eukaryotic Gene Expression, Maryland 21702-1201.
Genetics. 1992 Jun;131(2):287-96. doi: 10.1093/genetics/131.2.287.
The mat2-P and mat3-M loci of fission yeast contain respectively the plus (P) and minus (M) mating-type information in a transcriptionally silent state. That information is transposed from the mat2 or mat3 donor locus via recombination into the expressed mating-type locus (mat1) resulting in switching of the cellular mating type. We have identified a gene, named clr1 (for cryptic loci regulator), whose mutations allow expression of the mat2 and mat3 loci. clr1 mutants undergo aberrant haploid meiosis, indicative of transcription of the silent genes. Production of mRNA from mat3 is detectable in clr1 mutants. Furthermore, the ura4 gene inserted near mat3, weakly expressed in wild-type cells, is derepressed in clr1 mutants. The clr1 mutations also permit meiotic recombination in the 15-kb mat2-mat3 interval, where recombination is normally inhibited. The clr1 locus is in the right arm of chromosome II. We suggest that clr1 regulates silencing of the mat2 and mat3 loci, and participates in establishing the "cold spot" for recombination by organizing the chromatin structure of the mating-type region.
裂殖酵母的mat2 - P和mat3 - M基因座分别以转录沉默状态包含正（P）型和负（M）型交配型信息。该信息通过重组从mat2或mat3供体基因座转移到表达的交配型基因座（mat1），导致细胞交配型的转换。我们鉴定出一个名为clr1（隐秘基因座调节因子）的基因，其突变会使mat2和mat3基因座得以表达。clr1突变体经历异常的单倍体减数分裂，这表明沉默基因发生了转录。在clr1突变体中可检测到来自mat3的mRNA产生。此外，插入mat3附近的ura4基因在野生型细胞中表达较弱，在clr1突变体中则被去抑制。clr1突变还允许在15kb的mat2 - mat3区间内进行减数分裂重组，而该区间的重组通常受到抑制。clr1基因座位于染色体II的右臂。我们认为clr1调节mat2和mat3基因座的沉默，并通过组织交配型区域的染色质结构参与建立重组的“冷点”。
