Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA.
Mol Cell. 2011 Mar 4;41(5):543-53. doi: 10.1016/j.molcel.2011.02.006.
Eukaryotic cells license far more origins than are actually used for DNA replication, thereby generating a large number of dormant origins. Accumulating evidence suggests that such origins play a role in chromosome stability and tumor suppression, though the underlying mechanism is largely unknown. Here, we show that a loss of dormant origins results in an increased number of stalled replication forks, even in unchallenged S phase in primary mouse fibroblasts derived from embryos homozygous for the Mcm4(Chaos3) allele. We found that this allele reduces the stability of the MCM2-7 complex, but confers normal helicase activity in vitro. Despite the activation of multiple fork recovery pathways, replication intermediates in these cells persist into M phase, increasing the number of abnormal anaphase cells with lagging chromosomes and/or acentric fragments. These findings suggest that dormant origins constitute a major pathway for stalled fork recovery, contributing to faithful chromosome segregation and tumor suppression.
真核细胞许可的复制起始点远远超过实际用于 DNA 复制的起始点，从而产生了大量休眠的复制起始点。越来越多的证据表明，这些起始点在染色体稳定性和肿瘤抑制中发挥作用，尽管其潜在机制在很大程度上尚不清楚。在这里，我们表明休眠起始点的丢失会导致更多停滞的复制叉，即使在源自 Mcm4(Chaos3)等位基因纯合胚胎的原代小鼠成纤维细胞中未受到挑战的 S 期也是如此。我们发现，该等位基因降低了 MCM2-7 复合物的稳定性，但在体外赋予了正常的解旋酶活性。尽管激活了多种叉恢复途径，但这些细胞中的复制中间体仍然存在于 M 期，增加了具有滞后染色体和/或无着丝粒片段的异常后期细胞的数量。这些发现表明休眠的复制起始点是停滞叉恢复的主要途径，有助于忠实的染色体分离和肿瘤抑制。
