Inner nuclear membrane protein Lem2 facilitates Rad3-mediated checkpoint signaling under replication stress induced by nucleotide depletion in fission yeast.
Inner nuclear membrane protein Lem2 facilitates Rad3-mediated checkpoint signaling under replication stress induced by nucleotide depletion in fission yeast.
复制标题
在裂殖酵母中核苷酸耗尽诱导的复制应激下，内核膜蛋白 Lem2 促进 Rad3 介导的检查点信号传导。
DOI：
10.1016/j.cellsig.2015.12.009
复制
发表时间：
2016
影响因子：
4.8
通讯作者：
Xu,Yong-Jie
中科院分区：
文献类型：
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作者：
Xu,Yong-Jie
DNA复制检查点是一条高度保守的细胞信号通路，对维持真核生物基因组的完整性至关重要。当DNA复制受到干扰时，它就会被激活。在裂殖酵母中，扰动的复制叉会激活传感器激酶Rad3(ATR/Mec1)，后者与介体mRc1和9-1-1检查点钳协同工作，使效应蛋白激酶CDs1(Chk2/Rad53)磷酸化。CDS1的磷酸化促进了该激酶的自动激活。被激活的CDS1从叉子扩散出去，并在复制压力下刺激大多数检查点反应。虽然这个信号通路在分裂酵母中已经被很好地理解了，但是这个信号是如何被启动并因此被调控的仍然不完全清楚。先前的研究表明，Flem2+的缺失会使细胞对核糖核苷酸还原酶抑制剂羟基脲敏感。然而，其潜在的机制仍未得到很好的理解。这项研究表明，在羟基脲存在的情况下，Lem2促进了Rad3介导的CDS1激活的检查点信号。如果没有Lem2，所有已知的对复制检查点信号至关重要的Rad3依赖的磷酸化都会严重受损，这可能会导致在这个突变体中观察到异常的有丝分裂和药物敏感性。有趣的是，突变体对DNA损伤不是很敏感，DNA损伤检查点基本上保持完整，这表明Lem2的主要功能是促进检查点信号转导，以响应复制压力。由于Lem2是一种内核膜蛋白，这些结果也表明复制检查点可能在核内受到空间调控，这是以前未知的机制。
DNA replication checkpoint is a highly conserved cellular signaling pathway critical for maintaining genome integrity in eukaryotes. It is activated when DNA replication is perturbed. In Schizosaccharomyces pombe, perturbed replication forks activate the sensor kinase Rad3 (ATR/Mec1), which works cooperatively with mediator Mrc1 and the 9-1-1 checkpoint clamp to phosphorylate the effector kinase Cds1 (CHK2/Rad53). Phosphorylation of Cds1 promotes autoactivation of the kinase. Activated Cds1 diffuses away from the forks and stimulates most of the checkpoint responses under replication stress. Although this signaling pathway has been well understood in fission yeast, how the signaling is initiated and thus regulated remains incompletely understood. Previous studies have shown that deletion oflem2+sensitizes cells to the inhibitor of ribonucleotide reductase, hydroxyurea. However, the underlying mechanism is still not well understood. This study shows that in the presence of hydroxyurea, Lem2 facilitates Rad3-mediated checkpoint signaling for Cds1 activation. Without Lem2, all known Rad3-dependent phosphorylations critical for replication checkpoint signaling are seriously compromised, which likely causes the aberrant mitosis and drug sensitivity observed in this mutant. Interestingly, the mutant is not very sensitive to DNA damage and the DNA damage checkpoint remains largely intact, suggesting that the main function of Lem2 is to facilitate checkpoint signaling in response to replication stress. Since Lem2 is an inner nuclear membrane protein, these results also suggest that the replication checkpoint may be spatially regulated inside the nucleus, a previously unknown mechanism.