Jamil Sarwat, Mojtabavi Shadi, Hojabrpour Payman, Cheah Stefanie, Duronio Vincent
Department of Medicine, University of British Columbia and Vancouver Coastal Health Research Institute, Vancouver, BC, V6H 3Z6 Canada.
Mol Biol Cell. 2008 Aug;19(8):3212-20. doi: 10.1091/mbc.e07-11-1171. Epub 2008 May 21.
Here we report a novel role for myeloid cell leukemia 1 (Mcl-1), a Bcl-2 family member, in regulating phosphorylation and activation of DNA damage checkpoint kinase, Chk1. Increased expression of nuclear Mcl-1 and/or a previously reported short nuclear form of Mcl-1, snMcl-1, was observed in response to treatment with low concentrations of etoposide or low doses of UV irradiation. We showed that after etoposide treatment, Mcl-1 could coimmunoprecipitate with the regulatory kinase, Chk1. Chk1 is a known regulator of DNA damage response, and its phosphorylation is associated with activation of the kinase. Transient transfection with Mcl-1 resulted in an increase in the expression of phospho-Ser345 Chk1, in the absence of any evidence of DNA damage, and accumulation of cells in G2. Importantly, knockdown of Mcl-1 expression abolished Chk1 phosphorylation in response to DNA damage. Mcl-1 could induce Chk1 phosphorylation in ATM-negative (ataxia telangectasia mutated) cells, but this response was lost in ATR (AT mutated and Rad3 related)-defective cells. Low levels of UV treatment also caused transient increases in Mcl-1 levels and an ATR-dependent phosphorylation of Chk1. Together, our results strongly support an essential regulatory role for Mcl-1, perhaps acting as an adaptor protein, in controlling the ATR-mediated regulation of Chk1 phosphorylation.
我们在此报告Bcl-2家族成员髓样细胞白血病1（Mcl-1）在调节DNA损伤检查点激酶Chk1的磷酸化和激活方面的新作用。在用低浓度依托泊苷或低剂量紫外线照射处理后，观察到核Mcl-1和/或先前报道的Mcl-1短核形式snMcl-1的表达增加。我们发现，依托泊苷处理后，Mcl-1可与调节激酶Chk1进行共免疫沉淀。Chk1是已知的DNA损伤反应调节因子，其磷酸化与激酶的激活相关。在没有任何DNA损伤证据的情况下，用Mcl-1进行瞬时转染导致磷酸化的Ser345 Chk1表达增加，并且细胞在G2期积累。重要的是，敲低Mcl-1表达可消除DNA损伤时Chk1的磷酸化。Mcl-1可在ATM阴性（共济失调毛细血管扩张突变）细胞中诱导Chk1磷酸化，但在ATR（AT突变和Rad3相关）缺陷细胞中这种反应消失。低水平的紫外线处理也会导致Mcl-1水平短暂升高以及Chk1的ATR依赖性磷酸化。总之，我们的结果有力地支持了Mcl-1在控制ATR介导的Chk1磷酸化调节中起重要调节作用，可能作为衔接蛋白发挥作用。
