Ganter B, Tan S, Richmond T J
Institut für Molekularbiologie und Biophysik, ETH-Hönggerberg, Zürich, Switzerland.
J Mol Biol. 1993 Dec 20;234(4):975-87. doi: 10.1006/jmbi.1993.1652.
Dimethyl sulfate, DNase I and micrococcal nuclease DNA cleavage were combined with the ligation-mediated polymerase chain reaction to obtain high resolution maps of the promoter regions for two cell-type-specific genes: the a-specific STE2 gene and the alpha-specific STE3 gene. We find that MCM1 binds in vivo in a-cells to a 16 bp P-box sequence located in the STE2 UAS. In alpha-cells, the footprint pattern is extended relative to a-cells, consistent with the additional binding of MAT alpha 2 to the sequences flanking each end of the P-box. A nucleosome was found adjacent to the P-box of the transcriptionally repressed a-specific STE2 UAS in alpha-cells, positioned so that the nucleosome overlaps the TATA-box. In contrast, such well-positioned nucleosomes were not found for the transcriptionally active STE2 UAS in a-cells, where instead the TATA box appears to be bound to the general transcription factor TFIID. These observations support the hypothesis that MAT alpha 2 repression of a-specific genes is mediated by nucleosomes, perhaps by exclusion of TFIID from the TATA-box.
将硫酸二甲酯、脱氧核糖核酸酶I和微球菌核酸酶DNA切割与连接介导的聚合酶链反应相结合，以获得两个细胞类型特异性基因启动子区域的高分辨率图谱：a特异性STE2基因和α特异性STE3基因。我们发现，MCM1在体内与位于STE2上游激活序列（UAS）中的一个16bp的P盒序列结合于a细胞中。在α细胞中，足迹模式相对于a细胞有所扩展，这与MATα2与P盒两端侧翼序列的额外结合一致。在α细胞中，发现一个核小体与转录抑制的a特异性STE2 UAS的P盒相邻，其位置使得核小体与TATA盒重叠。相比之下，在a细胞中具有转录活性的STE2 UAS未发现如此定位的核小体，在a细胞中TATA盒似乎与通用转录因子TFIID结合。这些观察结果支持这样的假设，即MATα2对a特异性基因的抑制是由核小体介导的，可能是通过将TFIID排除在TATA盒之外。
