Parviz F, Hall D D, Markwardt D D, Heideman W
School of Pharmacy, University of Wisconsin, Madison, Wisconsin 53706, USA.
J Bacteriol. 1998 Sep;180(17):4508-15. doi: 10.1128/JB.180.17.4508-4515.1998.
In Saccharomyces cerevisiae, the transition from the G1 phase of the mitotic cycle into S phase is controlled by a set of G1 cyclins that regulate the activity of the protein kinase encoded by CDC28. Yeast cells regulate progress through the G1/S boundary in response to nutrients, moving quickly through G1 in glucose medium and more slowly in poorer medium. We have examined connections between glucose and the level of the message encoding Cln3, a G1 cyclin. We found that glucose positively regulates CLN3 mRNA levels through a set of repeated AAGAAAAA (A2GA5) elements within the CLN3 promoter. Mutations in these sequences reduce both transcriptional activation and specific interaction between CLN3 promoter elements and proteins in yeast extracts. Creation of five point mutations, replacing the G's within these repeats with T's, in the CLN3 promoter substantially reduces CLN3 expression in glucose medium and inhibits the ability of the cells to maintain a constant size when shifted into glucose.
在酿酒酵母中，有丝分裂周期从G1期向S期的转变由一组G1细胞周期蛋白控制，这些蛋白调节由CDC28编码的蛋白激酶的活性。酵母细胞根据营养物质来调节通过G1/S边界的进程，在葡萄糖培养基中快速通过G1期，而在营养较差的培养基中则较慢。我们研究了葡萄糖与编码G1细胞周期蛋白Cln3的信使水平之间的联系。我们发现，葡萄糖通过CLN3启动子内一组重复的AAGAAAAA（A2GA5）元件正向调节CLN3 mRNA水平。这些序列中的突变会降低转录激活以及CLN3启动子元件与酵母提取物中蛋白质之间的特异性相互作用。在CLN3启动子中创建五个点突变，将这些重复序列中的G替换为T，会显著降低葡萄糖培养基中CLN3的表达，并抑制细胞在转移到葡萄糖中时维持恒定大小的能力。
