Departament de Biologia Cel·lular, Immunologia i Neurociències, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.
Cell Cycle. 2012 Oct 1;11(19):3627-37. doi: 10.4161/cc.21917. Epub 2012 Aug 30.
Accurate DNA replication is crucial for the maintenance of genome integrity. To this aim, cells have evolved complex surveillance mechanisms to prevent mitotic entry in the presence of partially replicated DNA. ATR and Chk1 are key elements in the signal transduction pathways of DNA replication checkpoint; however, other kinases also make significant contributions. We show here that the stress kinases p38 and JNK are activated when DNA replication is blocked, and that their activity allows S/M, but not G 2/M, checkpoint maintenance when Chk1 is inhibited. Activation of both kinases by DNA replication inhibition is not mediated by the caffeine-sensitive kinases ATR or ATM. Phosphorylation of MKK3/6 and MKK4, p38 and JNK upstream kinases was also observed upon DNA replication inhibition. Using a genetic approach, we dissected the p38 pathway and showed that both p38α and p38β isoforms collaborate to inhibit mitotic entry. We further defined MKK3/6 and MK2/3 as the key upstream and downstream elements in the p38 signaling cascade after replication arrest. Accordingly, we found that the stress signaling pathways collaborate with Chk1 to keep cyclin B1/Cdk1 complexes inactive when DNA replication is inhibited, thereby preventing cell cycle progression when DNA replication is stalled. Our results show a complex response to replication stress, where multiple pathways are activated and fulfill overlapping roles to prevent mitotic entry with unreplicated DNA.
准确的 DNA 复制对于维持基因组完整性至关重要。为此，细胞进化出了复杂的监控机制，以防止在 DNA 部分复制的情况下进入有丝分裂。ATR 和 Chk1 是 DNA 复制检查点信号转导途径中的关键要素；然而，其他激酶也做出了重要贡献。我们在这里表明，当 DNA 复制受阻时，应激激酶 p38 和 JNK 被激活，并且当 Chk1 被抑制时，它们的活性允许 S/M，但不允许 G2/M 检查点维持。ATR 和 ATM 这两种咖啡因敏感激酶并不介导 DNA 复制抑制对这两种激酶的激活。还观察到 DNA 复制抑制后 MKK3/6 和 MKK4、p38 和 JNK 上游激酶的磷酸化。通过遗传方法，我们剖析了 p38 途径，并表明 p38α 和 p38β 同工型协同抑制有丝分裂进入。我们进一步定义 MKK3/6 和 MK2/3 为复制后抑制时 p38 信号级联中的关键上游和下游元件。因此，我们发现应激信号通路与 Chk1 合作，在 DNA 复制受阻时使细胞周期蛋白 B1/Cdk1 复合物保持失活，从而防止在 DNA 复制停滞时细胞周期进程。我们的研究结果表明，细胞对复制应激有一个复杂的反应，其中多个途径被激活并发挥重叠作用，以防止在存在未复制 DNA 的情况下进入有丝分裂。
