Bryans M, Valenzano M C, Stamato T D
Lankenau Medical Research Center, Wynnewood, PA 19096, USA.
Mutat Res. 1999 Jan 26;433(1):53-8. doi: 10.1016/s0921-8777(98)00063-9.
XR-1 is a CHO mutant cell line defective in double strand break repair and V(D)J recombination. These defects are due to a deletion of the XRCC4 gene which encodes a 38-kDa nuclear phosphoprotein. Recent studies have shown that XRCC4 interacts with and enhances the activity of DNA ligase IV in vitro. In this study we investigate the effect of the absence of XRCC4 on the level of DNA ligase IV in XR-1 cells. Western blot analysis indicates that levels of DNA ligase IV protein are almost undetectable in these cells, however, introduction of the XRCC4 cDNA into XR-1 resulted in a return to wild type levels of the protein. Furthermore, analysis of DNA ligase IV mRNA showed equivalent levels in both XR-1 and XRCC4 transfected XR-1 indicating that the altered level of DNA ligase IV is not due to a change in the expression of the gene. These data strongly suggest that an important function of XRCC4 is to stabilize the DNA ligase IV protein.
XR-1是一种在双链断裂修复和V(D)J重组方面存在缺陷的中国仓鼠卵巢（CHO）突变细胞系。这些缺陷是由于编码一种38 kDa核磷蛋白的XRCC4基因缺失所致。最近的研究表明，XRCC4在体外与DNA连接酶IV相互作用并增强其活性。在本研究中，我们调查了XRCC4缺失对XR-1细胞中DNA连接酶IV水平的影响。蛋白质免疫印迹分析表明，在这些细胞中几乎检测不到DNA连接酶IV蛋白的水平，然而，将XRCC4 cDNA导入XR-1细胞后，该蛋白水平恢复到了野生型水平。此外，对DNA连接酶IV mRNA的分析表明，XR-1细胞和转染了XRCC4的XR-1细胞中的mRNA水平相当，这表明DNA连接酶IV水平的改变并非由于该基因表达的变化。这些数据强烈表明，XRCC4的一个重要功能是稳定DNA连接酶IV蛋白。
