Roles of 53BP1 in progression of apoptosis

P53结合蛋白-1(53BP1)促进DNA双链断裂的非同源末端连接修复。在这项研究中，我们研究了53BP1和p53在凋亡细胞中的功能相互作用。我们发现53BP1以caspase依赖的方式被切割成53BP1的片段。在野生型和突变型p53的细胞中都观察到53BP1的裂解。部分53BP1片段定位于凋亡细胞表面，提示53BP1在巨噬细胞清除凋亡细胞中的作用。53BP1的下调减少了几个P53靶基因的转录。然而，这些基因中p53与启动子的结合不受53BP1下调的影响，提示53BP1通过调节靶基因中p53对启动子的修饰来调节p53的转录活性。

p53 binding protein-1 (53BP1) facilitates non-homologous end joining repair of DNA double-strand breaks. In this study, we examined functional interaction between 53BP1 and p53 in apoptotic cells. We found that 53BP1 is cleaved into a fragment of 53BP1 in a caspase-dependent manner. 53BP1 cleavage is observed in both cells with wild-type and mutant p53. Some of the 53BP1 fragments are localized on the surface of apoptotic cells, suggesting a role of 53BP1 in elimination of apoptotic cells by a macrophage. Downregulation of 53BP1 reduces transcription of several p53 target genes. However, binding of p53 on the promoter in these genes is not affected by 53BP1 downregulation, suggesting that 53BP1 regulates transcriptional activity of p53 by regulating modification of p53 on the promoter in the target genes.