Inhibition of ribonucleotide reductase (RNR), the rate-limiting enzyme in the synthesis of deoxyribonucleotides, causes DNA replication stress and activates the ataxia telangiectasia and rad3-related protein (ATR)-checkpoint kinase 1 (CHK1) pathway.
Mechanistically, MARS preferentially bound to and modified ataxia-telangiectasia and Rad3-related protein (ATR), inhibited ATR and its downstream effectors checkpoint kinase-1 and p53, and relieved cell-cycle arrest and decreased DNA damage-induced apoptosis by disrupting the binding of ATR-interacting protein to ATR.
Here we report a chain of events triggered by multiple splicing factor mutations, especially high-risk alleles in SRSF2 and U2AF1, including elevated R-loops, replication stress, and activation of the ataxia telangiectasia and Rad3-related protein (ATR)-Chk1 pathway.
Here, we investigate roles of nuclear PPIs in DNA damage response by sequestering specific PPIs with the expression of nuclear-targeted PH domains, which inhibits recruitment of Ataxia telangiectasia and Rad3-related protein (ATR) and reduces activation of Chk1.
We identified for the first time that EBV infection of TBCs induces a period of hyperproliferation 48-96 hours post infection characterized by the activation of ataxia telangiectasia and Rad3-releated (ATR) and checkpoint kinase-1 (Chk1).
5‑FU treatment induced DNA damage and activation of ataxia telangiectasia mutated (ATM) and Chk1, leading to S‑phase arrest, and Chk1 inhibition using SB218078 reduced S‑phase arrest and increased apoptosis in the presence of 5‑FU.
Dexrazoxane induced DNA damage responses, shown by enhanced levels of γ-H2AX/53BP1 foci, ATM (ataxia telangiectasia mutated), ATR (ATM and Rad3-related), Chk1 and Chk2 phosphorylation, and by p53 accumulation.
Furthermore, this growth arrest by piperine treatment was associated with DNA damage as indicated by phosphorylation of H2AX at Ser139, activation of ataxia telangiectasia and rad3-related protein (ATR) and checkpoint kinase 1 (Chk1).
To increase the efficacy of these treatments, inhibitors of the major components of the DDR such as ATM (ataxia telangiectasia mutated), ATR (ATM and Rad3-related), DNA-PK (DNA-dependent protein kinase, catalytic subunit), Chk1 (checkpoint protein 1) and Chk2 (checkpoint protein 2) have been used to confer radio- and/or chemosensitivity upon cancer cells.
Inhibitors of Chk1 and siRNA directed against ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia Rad3-related (ATR) pathways significantly reduced viral episomes, suggesting that these pathways play a role in maintaining HPV episome stability.
Here, using pair-matched wild-type p53 CDDP-sensitive (OV2008) and -resistant (C13*) cells, and p53-compromised CDDP-resistant cells (A2780cp, OCC-1, OVCAR-3 and SKOV3), we have demonstrated (i) the existence of site-specific differences in phospho-Ser-Chk1 content between sensitive and resistant cells in response to CDDP; (ii) PPM1D, but not phosphoinositide-3-kinase-related kinase Ataxia Telangiectasia and Rad3 related protein (ATR), is important in the regulation of CDDP-induced Chk1 activation and OVCA cell chemosensitivity; (iii) PPM1D downregulation sensitizes resistant cells to CDDP primarily by activating Chk1 and p53.
Western blotting revealed that CHK1 was constitutively phosphorylated at the ataxia telangiectasia response kinase target site Ser345 and the autophosphorylation site Ser296 in neuroblastoma cell lines.
We have investigated the effect of hyperoxia on DNA damage signaling and show that hyperoxia is a unique stress that activates the ataxia telangiectasia mutant (ATM)- and Rad3-related protein kinase (ATR)-dependent p53 phosphorylations (Ser6, -15, -37, and -392), phosphorylation of histone H2AX (Ser139), and phosphorylation of checkpoint kinase 1 (Chk1).