Autoregulatory mechanisms of phosphorylation of checkpoint kinase 1.
Autoregulatory mechanisms of phosphorylation of checkpoint kinase 1.
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DOI：
10.1158/0008-5472.can-12-0523
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发表时间：
2012-08-01
期刊：
影响因子：
11.2
通讯作者：
Zhang Y
中科院分区：
文献类型：
--
作者：
Wang J;Han X;Zhang Y
Chk1, a serine/threonine protein kinase, is centrally involved in cell cycle checkpoints and cellular response to DNA damage. Phosphorylation of Chk1 at two Ser/Gln (SQ) sites, Ser-317 and Ser-345, by the upstream kinase ATR is critical for checkpoint activation. However, the precise molecular mechanisms controlling Chk1 phosphorylation and subsequent checkpoint activation are not well understood. Here, we report unique auto-regulatory mechanisms that control protein phosphorylation of human Chk1, as well as checkpoint activation and cell viability. Phosphorylation of Ser-317 is a prerequisite, but not sufficient, for maximal phosphorylation at Ser-345. The amino (N)- terminal kinase domain of Chk1 prevents Chk1 phosphorylation at the carboxyl (C) terminus by ATR in the absence of DNA damage. Loss of the inhibitory effect imposed by the N-terminus causes constitutive phosphorylation of Chk1 by ATR under normal growth conditions, which in turn triggers artificial checkpoints that suppress the S phase progression. Using mutagenesis, we identified two point mutations that render Chk1 constitutively active. Unexpectedly, we found that expression of the constitutively active mutant form of Chk1 inhibited cancer cell proliferation, representing a novel strategy in suppressing tumor growth. Together, these studies revealed unique regulatory mechanisms of Chk1 phosphorylation and its implications in cancer therapy.
