Weiss K, Simpson R T
Department of Biochemistry and Molecular Biology and Center for Gene Regulation, Penn State University, University Park 16802, USA.
EMBO J. 1997 Jul 16;16(14):4352-60. doi: 10.1093/emboj/16.14.4352.
Switching of mating type in Saccharomyces cerevisiae is directional; MAT alpha cells recombine to transfer information from HMRa while MATa cells switch using the silent cassette at HML alpha. Genetic analysis recently has defined a 700 bp recombination enhancer approximately 29 kb from the left end of chromosome III that is necessary for directionality. The chromatin structure of this region differs strikingly in a- and alpha-cells. Mat alpha2p organizes a 3.7 kb chromatin domain that opposes interaction of trans-acting proteins with the enhancer. In a-cells lacking the alpha2 repressor, two footprinted regions flank an approximately 100 bp section having a unique DNA structure. This structural signature probably reflects interactions of proteins that result in directional mating type switching.
酿酒酵母中交配型的转换是有方向性的；MATα细胞通过重组从HMRa转移信息，而MATa细胞则利用HMLα处的沉默盒进行转换。近期的遗传分析确定了一个位于第三条染色体左端约29 kb处的700 bp重组增强子，它是方向性所必需的。该区域的染色质结构在a细胞和α细胞中显著不同。Matα2p组织了一个3.7 kb的染色质结构域，该结构域阻碍反式作用蛋白与增强子的相互作用。在缺乏α2阻遏物的a细胞中，两个足迹区域位于一个具有独特DNA结构的约100 bp片段两侧。这种结构特征可能反映了导致方向性交配型转换的蛋白质相互作用。
