Matsumoto T, Ohtani-Fujita N, Sowa Y, Bai F, Nikaido T, Tamaki T, Sakai T
Department of Preventive Medicine, Kyoto Prefectural University of Medicine.
Jpn J Cancer Res. 1998 Jun;89(6):626-33. doi: 10.1111/j.1349-7006.1998.tb03264.x.
A universal inhibitor of cyclin-dependent kinases, WAF1/Cip1 can dephosphorylate the RB gene product to arrest the cell cycle at the G1 phase. Here we show that the mRNA level and the promoter activities of the RB and WAF1/Cip1 genes exhibit cell cycle-dependent change when cells are released from either serum-starvation or the confluent cell state with serum. RB expression and promoter activity are elevated at middle to late G1. In contrast, the mRNA and promoter activity of the WAF1/Cip1 gene increase at early G1. These results suggest that the RB and WAF1/Cip1 expression and promoter activities depend not only on serum, but also on the cell cycle progression itself. Moreover, we identified the responsive region for serum-released cell cycle progression in the RB promoter and mapped it to the region between -4 and -182 relative to the initiating codon of the RB gene. The region in the WAF1/Cip1 promoter responsible for the serum-released cell cycle progression mapped not to the p53 binding site, but to the 374 base-pair region between -1770 and -1396 from the transcription start site.
细胞周期蛋白依赖性激酶的通用抑制剂WAF1/Cip1可使RB基因产物去磷酸化，从而将细胞周期阻滞在G1期。我们在此表明，当细胞从血清饥饿状态或血清存在下的汇合细胞状态中释放时，RB和WAF1/Cip1基因的mRNA水平及启动子活性呈现出细胞周期依赖性变化。RB的表达及启动子活性在G1期中期至后期升高。相比之下，WAF1/Cip1基因的mRNA及启动子活性在G1期早期增加。这些结果表明，RB和WAF1/Cip1的表达及启动子活性不仅取决于血清，还取决于细胞周期进程本身。此外，我们在RB启动子中鉴定出了对血清释放的细胞周期进程有反应的区域，并将其定位到相对于RB基因起始密码子的-4至-182区域。WAF1/Cip1启动子中负责血清释放的细胞周期进程的区域并非定位到p53结合位点，而是定位到转录起始位点-1770至-1396之间的374个碱基对区域。
