Department of Molecular Genetics, University of Toronto, Toronto, Canada.
J Cell Sci. 2012 Jan 1;125(Pt 1):133-43. doi: 10.1242/jcs.089938. Epub 2012 Jan 16.
Mini-chromosome maintenance complex-binding protein (MCM-BP) was discovered as a protein that is strongly associated with human MCM proteins, known to be crucial for DNA replication in providing DNA helicase activity. The Xenopus MCM-BP homologue appears to play a role in unloading MCM complexes from chromatin after DNA synthesis; however, the importance of MCM-BP and its functional contribution to human cells has been unclear. Here we show that depletion of MCM-BP by sustained expression of short hairpin RNA (shRNA) results in highly abnormal nuclear morphology and centrosome amplification. The abnormal nuclear morphology was not seen with depletion of other MCM proteins and was rescued with shRNA-resistant MCM-BP. MCM-BP depletion was also found to result in transient activation of the G2 checkpoint, slowed progression through G2 and increased replication protein A foci, indicative of replication stress. In addition, MCM-BP depletion led to increased cellular levels of MCM proteins throughout the cell cycle including soluble MCM pools. The results suggest that MCM-BP makes multiple contributions to human cells that are not limited to unloading of the MCM complex.
微小染色体维持复合物结合蛋白（MCM-BP）最初是作为一种与人类 MCM 蛋白强烈相关的蛋白而被发现的，已知其在提供 DNA 解旋酶活性方面对于 DNA 复制至关重要。爪蟾 MCM-BP 同源物似乎在 DNA 合成后从染色质上卸载 MCM 复合物中发挥作用；然而，MCM-BP 的重要性及其对人类细胞的功能贡献尚不清楚。在这里，我们通过持续表达短发夹 RNA（shRNA）表明，MCM-BP 的耗竭会导致高度异常的核形态和中心体扩增。其他 MCM 蛋白的耗竭不会导致异常核形态，而具有 shRNA 抗性的 MCM-BP 则可以挽救该异常核形态。MCM-BP 的耗竭还导致 G2 检查点的短暂激活、G2 期进展缓慢以及复制蛋白 A 焦点增加，表明存在复制应激。此外，MCM-BP 的耗竭还导致整个细胞周期中细胞内 MCM 蛋白水平增加，包括可溶性 MCM 池。结果表明，MCM-BP 对人类细胞有多种贡献，而不仅仅是卸载 MCM 复合物。
