BRCA1-associated exclusion of 53BP1 from DNA damage sites underlies temporal control of DNA repair
BRCA1-associated exclusion of 53BP1 from DNA damage sites underlies temporal control of DNA repair
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DOI：
10.1242/jcs.105353
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发表时间：
2012-08-01
影响因子：
4
通讯作者：
Jackson, Stephen P.
中科院分区：
文献类型：
--
作者：
Chapman, J. Ross;Sossick, Alex J.;Jackson, Stephen P.
辐射后，许多 DNA 损伤响应蛋白迅速重新分布成显微镜可见的亚核聚集体，称为电离辐射诱导灶 (IRIF)。受损染色质上蛋白质的富集实际上与 DNA 修复有何关系仍不清楚。在这里，我们使用超分辨率显微镜以亚衍射极限分辨率检查单个 IRIF 内 BRCA1 和 53BP1 蛋白的空间分布，产生前所未有的细节增加，这是传统显微镜以前无法看到的。与 53BP1 通过非同源末端连接促进 DNA 双链断裂修复的作用一致，IRIF 中的 53BP1 富集在 G0/G1 细胞周期阶段最为突出，在该阶段富集于致密的球状结构。相比之下，当细胞过渡到 S 期时，BRCA1 被招募到 IRIF 的核心，这与 53BP1 被排除在焦点外围相关，导致 53BP1 在 DNA 损伤位点的占据总体减少。我们的数据表明，BRCA1 相关的 IRIF 核心对应于与同源重组修复相关的染色质区域，并且 IRIF 中 BRCA1 的富集代表了 DNA 修复程序中的时间转换。我们认为，BRCA1 通过抑制其与损伤位点附近染色质的相互作用来拮抗 S 期 53BP1 依赖性 DNA 修复。此外，BRCA1 缺陷细胞表现出的基因组不稳定性可能是由于在 S 期未能有效地将 53BP1 从这些区域排除而导致的。
Following irradiation, numerous DNA-damage-responsive proteins rapidly redistribute into microscopically visible subnuclear aggregates, termed ionising-radiation-induced foci (IRIF). How the enrichment of proteins on damaged chromatin actually relates to DNA repair remains unclear. Here, we use super-resolution microscopy to examine the spatial distribution of BRCA1 and 53BP1 proteins within single IRIF at subdiffraction-limit resolution, yielding an unprecedented increase in detail that was not previously apparent by conventional microscopy. Consistent with a role for 53BP1 in promoting DNA double-strand break repair by non-homologous end joining, 53BP1 enrichment in IRIF is most prominent in the G0/G1 cell cycle phases, where it is enriched in dense globular structures. By contrast, as cells transition through S phase, the recruitment of BRCA1 into the core of IRIF is associated with an exclusion of 53BP1 to the focal periphery, leading to an overall reduction of 53BP1 occupancy at DNA damage sites. Our data suggest that the BRCA1-associated IRIF core corresponds to chromatin regions associated with repair by homologous recombination, and the enrichment of BRCA1 in IRIF represents a temporal switch in the DNA repair program. We propose that BRCA1 antagonises 53BP1-dependent DNA repair in S phase by inhibiting its interaction with chromatin proximal to damage sites. Furthermore, the genomic instability exhibited by BRCA1-deficient cells might result from a failure to efficiently exclude 53BP1 from such regions during S phase.