“关键DNA损伤反应蛋白”53BP1通过在一个双链断裂点上与染色质结合来发挥作用。以前的研究显示，53BP1在由RNF168所促进的一次“泛素化”事件后发挥作用，尽管其向断裂点上的吸收过去被认为只取决于组蛋白H4K20的甲基化。Daniel Durocher及其同事现在发现，53BP1的吸收涉及H4K20me2和组蛋白H2AK15“泛素化”的识别。该“泛素”标记以及H2A的周围环境是由53BP1的一个他们称之为“取决于泛素化的吸收主题”的区域读出的。（生物谷Bioon.com）
生物谷推荐英文摘要：
Nature doi:10.1038/nature12318
53BP1 is a reader of the DNA-damage-induced H2A Lys 15 ubiquitin mark
Amélie Fradet-Turcotte,Marella D. Canny,Cristina Escribano-Díaz,Alexandre Orthwein, Charles C. Y. Leung,Hao Huang, Marie-Claude Landry, Julianne Kitevski-LeBlanc,Sylvie M. Noordermeer,Frank Sicheri & Daniel Durocher
53BP1 (also called TP53BP1) is a chromatin-associated factor that promotes immunoglobulin class switching and DNA double-strand-break (DSB) repair by non-homologous end joining. To accomplish its function in DNA repair, 53BP1 accumulates at DSB sites downstream of the RNF168 ubiquitin ligase. How ubiquitin recruits 53BP1 to break sites remains unknown as its relocalization involves recognition of histone H4 Lys20 (H4K20) methylation by its Tudor domain. Here we elucidate how vertebrate 53BP1 is recruited to the chromatin that flanks DSB sites. We show that 53BP1 recognizes mononucleosomes containing dimethylated H4K20 (H4K20me2) and H2A ubiquitinated on Lys15 (H2AK15ub), the latter being a product of RNF168 action on chromatin. 53BP1 binds to nucleosomes minimally as a dimer using its previously characterized methyl-lysine-binding Tudor domain and a carboxy-terminal extension, termed the ubiquitination-dependent recruitment (UDR) motif, which interacts with the epitope formed by H2AK15ub and its surrounding residues on the H2A tail. 53BP1 is therefore a bivalent histone modification reader that recognizes a histone ‘code’ produced by DSB signalling.
