Kanazawa S, Fujiwara Y, Mizuno K
Department of Orthopedic Surgery, Kobe University School of Medicine.
Kobe J Med Sci. 1994 Dec;40(5-6):165-74.
Normal human diploid TIG-1 fibroblasts underwent replicative senescence around 64-68 population doubling levels (PDL) by the irreversible serum-unresponsive G1-growth arrest. Repression of growth-promoting genes was searched in this study. The RT-PCR and Western blot analyses have shown that in senescent TIG-1 cells at PDL64-67, cdk2 and cyclin E were selectively repressed at the mRNA and protein levels even after serum stimulation, and cdc2 and cyclin A were less repressed than cdk2 and cyclin E. Such a specific lack of cdk2 and cyclin E proteins correlated with unphosphorylation of the retinoblastoma gene product (pRB) in senescent cells. Transcription factor E2F1 was also completely repressed at the mRNA and protein levels in senescent TIG-1 cells. Middle-passage cells exhibited active expressions of all the above genes and pRB phosphorylation. Therefore, the present results have indicated the selective repressions of cdk2, cyclin E and E2F1 in senescent cells.
正常人类二倍体TIG-1成纤维细胞在约64-68个群体倍增水平（PDL）时通过不可逆的血清无反应性G1期生长停滞进入复制性衰老。本研究旨在探寻促进生长基因的抑制情况。逆转录-聚合酶链反应（RT-PCR）和蛋白质免疫印迹分析表明，在PDL64-67的衰老TIG-1细胞中，即使在血清刺激后，细胞周期蛋白依赖性激酶2（cdk2）和细胞周期蛋白E在mRNA和蛋白质水平上也被选择性抑制，而细胞周期蛋白依赖性激酶2（cdc2）和细胞周期蛋白A的抑制程度低于cdk2和细胞周期蛋白E。衰老细胞中cdk2和细胞周期蛋白E蛋白的这种特异性缺乏与视网膜母细胞瘤基因产物（pRB）的去磷酸化相关。转录因子E2F1在衰老的TIG-1细胞的mRNA和蛋白质水平上也被完全抑制。中期传代细胞表现出上述所有基因的活跃表达和pRB磷酸化。因此，目前的结果表明衰老细胞中cdk,2、细胞周期蛋白E和E2F1受到选择性抑制。
