ATM regulates Cdt1 stability during the unperturbed S phase to prevent re-replication
Satoko Iwahori1, Daisuke Kohmon2, Junya Kobayashi3
1Virology Division; National Cancer Center Research Institute; Chuohku, Tokyo, Japan.
Abstract:
Ataxia-telangiectasia mutated (ATM) plays crucial roles in DNA damage responses, especially with regard to DNA double-strand breaks (DSBs). However, it appears that ATM can be activated not only by DSB, but also by some changes in chromatin architecture, suggesting potential ATM function in cell cycle control. Here, we found that ATM is involved in timely degradation of Cdt1, a critical replication licensing factor, during the unperturbed S phase. At least in certain cell types, degradation of p27(Kip1) was also impaired by ATM inhibition. The novel ATM function for Cdt1 regulation was dependent on its kinase activity and NBS1. Indeed, we found that ATM is moderately phosphorylated at Ser1981 during the S phase. ATM silencing induced partial reduction in levels of Skp2, a component of SCF(Skp2) ubiquitin ligase that controls Cdt1 degradation. Furthermore, Skp2 silencing resulted in Cdt1 stabilization like ATM inhibition. In addition, as reported previously, ATM silencing partially prevented Akt phosphorylation at Ser473, indicative of its activation, and Akt inhibition led to modest stabilization of Cdt1. Therefore, the ATM-Akt-SCF(Skp2) pathway may partly contribute to the novel ATM function. Finally, ATM inhibition rendered cells hypersensitive to induction of re-replication, indicating importance for maintenance of genome stability.
Insights
The study reveals a new role for Ataxia-telangiectasia mutated (ATM) in regulating Cdt1 degradation during S phase, crucial for preventing DNA re-replication and maintaining genome stability.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Ataxia-telangiectasia mutated (ATM) is a key kinase in DNA damage response, particularly for DNA double-strand breaks (DSBs).
- ATM activation by chromatin changes suggests roles beyond DSB repair, potentially in cell cycle control.
Purpose of the Study:
- To investigate the novel function of ATM in regulating cell cycle progression during unperturbed S phase.
- To elucidate the molecular mechanisms underlying ATM's role in Cdt1 degradation and its impact on genome stability.
Main Methods:
- ATM silencing and inhibition were used to assess effects on Cdt1 and p27(Kip1) degradation.
- Analysis of ATM phosphorylation, NBS1 interaction, and Skp2 levels.
- Investigated the ATM-Akt-SCF(Skp2) pathway involvement.
- Assessed cellular response to re-replication induction after ATM inhibition.
Main Results:
- ATM regulates timely Cdt1 degradation during S phase, dependent on its kinase activity and NBS1.
- ATM inhibition impairs Cdt1 and p27(Kip1) degradation and leads to re-replication.
- ATM influences Skp2 levels and Akt phosphorylation, suggesting a role in the ATM-Akt-SCF(Skp2) pathway.
- ATM activity is essential for preventing re-replication and maintaining genome stability.
Conclusions:
- ATM has a novel function in controlling Cdt1 degradation, essential for preventing re-replication.
- The ATM-Akt-SCF(Skp2) pathway is implicated in this novel ATM function.
- ATM plays a critical role in maintaining genome stability by regulating replication licensing factors.
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