Rad3 is the orthologue of ATR and the sensor kinase of the DNA replication checkpoint in Schizosaccharomyces pombe. Under replication stress, it initiates checkpoint signaling at the forks necessary for maintaining genome stability and cell survival. To better understand the checkpoint initiation process, we have carried out a genetic screen in fission yeast by random mutation of the genome, looking for mutants defective in response to the replication stress induced by hydroxyurea. In addition to the previously reported mutant with a C-to-Y change at position 307 encoded by tel2 (tel2-C307Y mutant) (Y.-J. Xu, S. Khan, A. C. Didier, M. Wozniak, et al., Mol Cell Biol 39:e00175-19, 2019, https://doi.org/10.1128/MCB.00175-19), this screen has identified six mutations in rqh1 encoding a RecQ DNA helicase. Surprisingly, these rqh1 mutations, except for a start codon mutation, are all in the helicase domain, indicating that the helicase activity of Rqh1 plays an important role in the replication checkpoint. In support of this notion, integration of two helicase-inactive mutations or deletion of rqh1 generated a similar Rad3 signaling defect, and heterologous expression of human RECQ1, BLM, and RECQ4 restored the Rad3 signaling and partially rescued a rqh1 helicase mutant. Therefore, the replication checkpoint function of Rqh1 is highly conserved, and mutations in the helicase domain of these human enzymes may cause the checkpoint defect and contribute to the cancer predisposition syndromes.

中文翻译：

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RecQ DNA解旋酶Rqh1在裂变酵母的DNA复制检查点途径中促进Rad3ATR激酶信号传导。

Rad3是粟酒裂殖酵母（Schizosaccharomyces pombe）中ATR的直向同源物和DNA复制检查点的传感器激酶。在复制压力下，它在维持基因组稳定性和细胞存活所必需的叉处启动检查点信号传导。为了更好地了解检查点的启动过程，我们通过基因组的随机突变在裂变酵母中进行了基因筛选，寻找对羟基脲诱导的复制应激有缺陷的突变体。除了先前报道的突变体之外，它在tel2（tel2-C307Y（Y.-J.Xu，S.Khan，AC Didier，M.Wozniak，et al。，Mol Cell Biol 39：e00175-19，2019，https://doi.org/10.1128/MCB.00175- 19），此筛选已在rqh1中识别出编码RecQ DNA解旋酶的六个突变。出乎意料的是，这些rqh1突变（除了起始密码子突变）都在解旋酶结构域中，这表明Rqh1的解旋酶活性在复制检查点中起着重要作用。为了支持该观点，两个解旋酶失活突变的整合或rqh1的缺失产生了类似的Rad3信号缺陷，人RECQ1，BLM和RECQ4的异源表达恢复了Rad3信号并部分拯救了rqh1解旋酶突变体。因此，Rqh1的复制检查点功能是高度保守的，并且这些人类酶的解旋酶结构域中的突变可能导致检查点缺陷，并导致癌症易感综合征。