Mammalian TIMELESS Is Required for ATM-dependent CHK2 Activation and G2/M Checkpoint Control

Xiaoming Yang,Patricia A Wood,William J.M Hrushesky

doi:10.1074/jbc.m109.050237

Xiaoming Yang, Patricia A Wood + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m109.050237

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Abstract

Timeless (Tim), a core circadian clock gene in Drosophila, is retained in mammals but has no apparent mammalian circadian clock function. Mammalian TIM is essential for ATR-dependent Chk1 activation and S-phase arrest. We report that TIM is likewise essential for ATM-dependent Chk2-mediated signaling of doxorubicin-induced DNA double strand breaks. TIM depletion attenuates doxorubicin-induced G(2)/M cell cycle arrest and sensitizes cancer cells to doxorubicin-induced cytotoxicity. TIM is, thereby, a potential novel anticancer drug target whose inhibition may enhance the therapeutic cytotoxicity of agents that activate DNA damage pathways as part of their mechanism.

Highlights

Timeless (Tim), a core circadian clock gene in Drosophila, is retained in mammals but has no apparent mammalian circadian clock function
We report that TIM is likewise essential for ATM-dependent Chk2-mediated signaling of doxorubicin-induced DNA double strand breaks
We find that TIM is not essential for ATM activation, it is required for ATMdependent activation of Chk[2] and G2/M checkpoint arrest

Summary

Introduction

Timeless (Tim), a core circadian clock gene in Drosophila, is retained in mammals but has no apparent mammalian circadian clock function. We report that TIM is likewise essential for ATM-dependent Chk2-mediated signaling of doxorubicin-induced DNA double strand breaks. Dox activates the ATMChk[2] DNA damage response pathway and arrests the cell cycle at the G2/M phase (30, 31). Doxorubicin-induced Chk[2] Thr[68] phosphorylation levels in control and TIM siRNA 2-treated HCT116 cells were compared.

Results

Conclusion