Grand R J, Ibrahim A P, Taylor A M, Milner A E, Gregory C D, Gallimore P H, Turnell A S
CRC Institute for Cancer Studies, University of Birmingham, Edgbaston, United Kingdom.
Virology. 1998 May 10;244(2):330-42. doi: 10.1006/viro.1998.9102.
It has previously been shown that following viral infection, Ad5 E1A induces cell cycle progression of quiescent rodent cells, leading to DNA synthesis and mitosis. Here we have examined the effect of Ad12 E1A on the cell cycle characteristics of human cells. Human tumor (A549, KB, and HeLa) cells were infected with Ad12 d/620, a mutant virus which has a lesion in the E1B gene and essentially expresses only E1A. These infected cells progressed from being largely in G1 into S phase, where they arrested. Even up to 96 h postinfection (p.i.) the cells remained blocked in S phase. DNA synthesis did, however, proceed in Ad12 d/620-infected cells, giving rise to multiple copies of cellular DNA. Similar results were obtained when primary human skin fibroblasts were infected, although the polyploidy was less marked. The expression of cyclins A, B1, and E in the tumor cells increased appreciably in response to E1A. In contrast, there was a dramatic reduction in the levels of cyclin D1 and D3. Increases in cyclin D1 expression could be detected at very late times p.i. In those cell lines expressing low levels of cdc2 and cdk2 an appreciable increase in expression was seen soon after Ad12 E1A could be detected. The elevated levels of cyclins A, B1, and E were associated with increased protein kinase activity directed against histone H1. An increase in cyclin D1-associated kinase activity against Rb1 was also observed at late times. This deregulation of the cell cycle was not solely dependent on E1A inactivation of Rb, since similar effects were seen in Ad12 d/620-infected retinoblastoma (Y-79) cells, implicating p107 and p130 in E1A-mediated changes in cell cycle progression. We propose that the E1A-induced levels of cyclins A, B1, and E by Ad12 E1A in human cells may lead to an uncoupling of S phase from cell cycle progression.
先前的研究表明，病毒感染后，腺病毒5型E1A可诱导静止的啮齿动物细胞进入细胞周期进程，从而导致DNA合成和有丝分裂。在此，我们研究了腺病毒12型E1A对人细胞周期特征的影响。人肿瘤（A549、KB和HeLa）细胞用腺病毒12 d/620感染，该突变病毒在E1B基因中有损伤，基本上只表达E1A。这些被感染的细胞从主要处于G1期进入S期，然后在S期停滞。即使在感染后96小时，细胞仍停滞在S期。然而，在腺病毒12 d/620感染的细胞中DNA合成仍在进行，产生了多拷贝的细胞DNA。当原代人皮肤成纤维细胞被感染时也得到了类似的结果，尽管多倍体现象不太明显。肿瘤细胞中细胞周期蛋白A、B1和E的表达因E1A而明显增加。相反，细胞周期蛋白D1和D3的水平显著降低。在感染后很晚的时间才能检测到细胞周期蛋白D1表达的增加。在那些表达低水平cdc2和cdk2的细胞系中，在检测到腺病毒12 E1A后不久，就可见表达明显增加。细胞周期蛋白A、B1和E水平的升高与针对组蛋白H1的蛋白激酶活性增加有关。在后期还观察到细胞周期蛋白D1相关激酶针对Rb1的活性增加。细胞周期的这种失调并不完全依赖于E1A对Rb的失活，因为在腺病毒12 d/620感染的视网膜母细胞瘤（Y-79）细胞中也观察到类似的效应，这表明p107和p130参与了E1A介导的细胞周期进程变化。我们提出，腺病毒12 E1A在人细胞中诱导的细胞周期蛋白A、B1和E水平可能导致S期与细胞周期进程解偶联。
