a Division of Molecular and Cellular Biology , National Institute for Child Health and Human Development , National Institutes of Health , Bethesda , MD 20892.
Cell Cycle. 2018;17(6):739-748. doi: 10.1080/15384101.2018.1442630. Epub 2018 Apr 5.
RCC1 associates to chromatin dynamically within mitosis and catalyzes Ran-GTP production. Exogenous RCC1 disrupts kinetochore structure in Xenopus egg extracts (XEEs), but the molecular basis of this disruption remains unknown. We have investigated this question, utilizing replicated chromosomes that possess paired sister kinetochores. We find that exogenous RCC1 evicts a specific subset of inner KT proteins including Shugoshin-1 (Sgo1) and the chromosome passenger complex (CPC). We generated RCC1 mutants that separate its enzymatic activity and chromatin binding. Strikingly, Sgo1 and CPC eviction depended only on RCC1's chromatin affinity but not its capacity to produce Ran-GTP. RCC1 similarly released Sgo1 and CPC from synthetic kinetochores assembled on CENP-A nucleosome arrays. Together, our findings indicate RCC1 regulates kinetochores at the metaphase-anaphase transition through Ran-GTP-independent displacement of Sgo1 and CPC.
RCC1 在有丝分裂过程中动态地与染色质结合，并催化 Ran-GTP 的产生。外源性 RCC1 会破坏爪蟾卵提取物（XEE）中的动粒结构，但这种破坏的分子基础尚不清楚。我们利用具有配对姐妹动粒的复制染色体研究了这个问题。我们发现外源性 RCC1 会驱逐特定的一组内动粒蛋白，包括 Shugoshin-1（Sgo1）和染色体乘客复合物（CPC）。我们生成了分离其酶活性和染色质结合的 RCC1 突变体。引人注目的是，Sgo1 和 CPC 的驱逐仅取决于 RCC1 的染色质亲和力，而不取决于其产生 Ran-GTP 的能力。RCC1 同样可以从组装在 CENP-A 核小体阵列上的合成动粒上释放 Sgo1 和 CPC。总之，我们的发现表明，RCC1 通过 Ran-GTP 独立的 Sgo1 和 CPC 置换来调节有丝分裂中期-后期转换中的动粒。
