Kim Seong-Tae
Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, 300 Chunchundong, Jangangu, Suwon, Kyonggido 440-746, Republic of Korea.
Biochem Biophys Res Commun. 2005 May 27;331(1):247-52. doi: 10.1016/j.bbrc.2005.03.162.
The Mre11-Rad50-Nbs1 protein complex has been known to be involved in a variety of DNA metabolic events that involve DNA double-strand breaks (DSBs). The phosphorylation of Mre11 is increased in response to ionizing radiation, which suggests that phosphorylation of Mre11 may be an important regulatory mechanism of this complex. Mre11-phosphorylating kinase activities were observed in Chk2 immunoprecipitates and HeLa nuclear extracts. Through the tandem affinity tagging system and conventional chromatography, this kinase was purified and identified as protein kinase CK2. CK2 phosphorylates Mre11 in vitro. In vitro kinase assay with a series of truncated Mre11 proteins as substrates for CK2 and site-directed mutagenesis showed that serine 649 of Mre11 is mainly phosphorylated by CK2 in vitro. In vivo labeling and phosphopeptide mapping analysis revealed that this phosphorylation occurs in vivo. These data implicate CK2 as a potential upstream regulator of Mre11 function.
已知Mre11-Rad50-Nbs1蛋白复合物参与多种涉及DNA双链断裂（DSB）的DNA代谢事件。Mre11的磷酸化在电离辐射后增加，这表明Mre11的磷酸化可能是该复合物的重要调节机制。在Chk2免疫沉淀物和HeLa细胞核提取物中观察到Mre11磷酸化激酶活性。通过串联亲和标签系统和传统色谱法，纯化了该激酶并鉴定为蛋白激酶CK2。CK2在体外使Mre11磷酸化。以一系列截短的Mre11蛋白作为CK2的底物进行体外激酶测定和定点诱变表明，Mre11的丝氨酸649在体外主要被CK2磷酸化。体内标记和磷酸肽图谱分析表明这种磷酸化发生在体内。这些数据表明CK2可能是Mre11功能的潜在上游调节因子。
