Mck1 defines a key S-phase checkpoint effector in response to various degrees of replication threats
Mck1 defines a key S-phase checkpoint effector in response to various degrees of replication threats
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Mck1定义了一个关键的S阶段检查点效应器，以应对不同程度的复制威胁
DOI：
10.1371/journal.pgen.1008136
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发表时间：
2019
期刊：
影响因子：
4.5
通讯作者：
Lou Huiqiang
中科院分区：
文献类型：
--
作者：
Li Xiaoli;Jin Xuejiao;Sharma Sushma;Liu Xiaojing;Zhang Jiaxin;Niu Yanling;Li Jiani;Li Zhen;Zhang Jingjing;Cao Qinhong;Hou Wenya;Du Li-Lin;Liu Beidong;Lou Huiqiang
S期检查点在调节核糖核苷酸还原酶(RNR)活性以维持dNTP池中发挥重要作用。真核细胞如何对不同水平的复制威胁做出适当的反应仍然是个谜。在这里，我们已经确定了保守的GSK-3激酶Mck1与Dun1合作调节这一过程。删除mk1使dun1Δ对羟基脲(HU)敏感，这使人想起mec1Δ或rAD53Δ。Mck1作为RND53下游的一种蛋白，不像Dun1那样参与RNR的翻译后调节，但Mck1可以通过磷酸化从RNR2/3/4的启动子中释放Crt1抑制因子。同时，Rnr2抑制剂Hug1被诱导微调dNTP水平。当细胞受到更严重的威胁时，Mck1可以抑制HUG1的转录。重要的是，只有联合缺失HUG1和CRT1，才能显著提高dNTP水平，并使致死剂量的HU攻击的McK1ΔDun1Δ或Mec1Δ细胞存活。这些发现揭示了Mck1和Dun1在S阶段的检查点途径中的分工，以微调dNTP的动态平衡。作者摘要四种dNTP的适量和平衡对于所有细胞正确地一代一代地复制和传递遗传物质至关重要。真核生物已经开发出一种警报和反应系统来应对这种干扰。在这里，我们发现了一个二级效应器分支。它被上游的监视激酶级联激活，从而诱导产生dNTP的酶的表达。它还可以减少这些酶的抑制物，根据威胁的程度进一步提高它们的活性。这些发现表明了一个多层次的反应系统来保证dNTP的供应，这对于在各种环境挑战下保持遗传稳定是必不可少的。
The S-phase checkpoint plays an essential role in regulation of the ribonucleotide reductase (RNR) activity to maintain the dNTP pools. How eukaryotic cells respond appropriately to different levels of replication threats remains elusive. Here, we have identified that a conserved GSK-3 kinase Mck1 cooperates with Dun1 in regulating this process. Deleting MCK1 sensitizes dun1Δ to hydroxyurea (HU) reminiscent of mec1Δ or rad53Δ. As a kinase at the downstream of Rad53, Mck1 does not participate in the post-translational regulation of RNR as Dun1 does, but Mck1 can release the Crt1 repressor from the promoters of RNR2/3/4 by phosphorylation. Meanwhile, Hug1, an Rnr2 inhibitor, is induced to fine-tune the dNTP levels. When cells suffer a more severe threat, Mck1 can inhibit the transcription of HUG1. Importantly, only a combined deletion of HUG1 and CRT1, can confer a dramatic boost of dNTP levels and the survival of mck1Δdun1Δ or mec1Δ cells assaulted by a lethal dose of HU. These findings reveal the division-of-labor between Mck1 and Dun1 at the S-phase checkpoint pathway to fine-tune dNTP homeostasis. Author Summary The appropriate amount and balance of four dNTPs are crucial for all cells correctly copying and passing on their genetic material generation by generation. Eukaryotes have developed an alert and response system to deal with the disturbance. Here, we uncovered a second-level effector branch. It is activated by the upstream surveillance kinase cascade, which can induce the expression of dNTP-producing enzymes. It can also reduce the inhibitor of these enzymes to further boost their activity according to the degrees of threats. These findings suggest a multi-level response system to guarantee dNTP supply, which is essential to maintain genetic stability under various environmental challenges.