p21waf1 can block cells at two points in the cell cycle, but does not interfere with processive DNA-replication or stress-activated kinases
p21waf1 can block cells at two points in the cell cycle, but does not interfere with processive DNA-replication or stress-activated kinases
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DOI：
10.1038/sj.onc.1201558
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发表时间：
1998-01-29
期刊：
影响因子：
8
通讯作者：
Rijksen, G
中科院分区：
文献类型：
--
作者：
Medema, RH;Klompmaker, R;Rijksen, G
p21(waf1) 已被证明可以介导 DNA 损伤剂诱导的 p53 依赖性生长停滞，p21(waf1) 的多种功能可能参与这种生长停滞。首先，p21(waf1) 是细胞周期蛋白依赖性激酶 (CDK) 的有效抑制剂。此外，p21(waf1) 可以与增殖细胞核抗原 (PCNA) 相互作用，从而抑制体外 DNA 复制。最后，据报道 p21(waf1) 可以抑制应激激活蛋白激酶 (SAPK)。为了研究 p21(waf1) 的这些多重功能，我们建立了 U2OS 衍生细胞系，其中 p21(waf1) 的表达可以通过培养基中四环素的浓度来调节。我们观察到诱导 p21(waf1) 表达后细胞生长几乎完全但可逆的抑制。 p21(waf1) 强烈抑制 [H-3] 胸苷掺入和 CDK2 活性。 p21(waf1) 诱导后，细胞积累了 2N 或 4N DNA 含量，表明 G1 和 G2 中的事件可以被 p21(waf1) 抑制。事实上，在 p21(waf1) 诱导后，与细胞周期蛋白 B 相关的激酶活性显着降低，尽管细胞周期蛋白 B 继续表达。相反，p21(waf1) 似乎并没有抑制 PCNA 在正在进行的 DNA 复制中的功能，因为表达高水平 p21(waf1) 的细胞显然在 S 期正常进展。此外，SAPK 的活性并未受到高水平 p21(waf1) 的显着影响。我们的结论是，至少在这些 U2OS 衍生细胞中，p21(waf1) 在 G1 和 G2 中充当 CDK 活性的抑制剂，但不是 PCNA 或 SAPK 的抑制剂。
p21(waf1) has been shown to mediate the p53-dependent growth arrest induced by DNA-damaging agents, Several functions have been ascribed to p21(waf1) that could be involved in this growth arrest, For one, p21(waf1) is an efficient inhibitor of cyclin-dependent kinases (CDKs). Also, p21(waf1) can interact with proliferating cell nuclear antigen (PCNA), and as such inhibit in vitro DNA-replication. Finally, p21(waf1) has been reported to inhibit stress-activated protein kinases (SAPKs). In order to study these multiple functions of p21(waf1) we have established U2OS-derived cell lines, in which the expression of p21(waf1) can be regulated by the concentration of tetracycline in the culture medium, We observed a virtually complete, but reversible inhibition of cell growth upon induction of p21(waf1)-expression. Both [H-3]thymidine-incorporation and CDK2-activity were strongly inhibited by p21(waf1). Upon induction of p21(waf1) cells accumulated with a 2N or 4N DNA content suggesting events in G1 and G2 can be inhibited by p21(waf1). Indeed, kinase activity associated with cyclin B was reduced dramatically upon induction of p21(waf1), although cyclin B continues to be expressed, In contrast, p21(waf1) does not seem to inhibit the function of PCNA in ongoing DNA replication, since cells expressing high levels of p21(waf1) apparently progressed normally through S-phase. Also, the activity of SAPKs was not substantially affected by the high levels of p21(waf1). We conclude that, at least in these U2OS-derived cells, p21(waf1) functions as an inhibitor of CDK-activity in G1 and G2, but not as an inhibitor of PCNA or SAPKs.