Polη, a Y-family translesion synthesis polymerase, promotes cellular tolerance of Myc-induced replication stress

Abstract

Growth of precancerous and cancer cells relies on their tolerance of oncogene-induced replication stress (RS). Translesion synthesis (TLS) plays an essential role in the cellular tolerance of various types of RS and bypasses replication barriers by employing specialized polymerases. However, limited information is available about the role of TLS polymerases in oncogene-induced RS. Here, we report that Polη, a Y-family TLS polymerase, promotes cellular tolerance of Myc-induced RS. Polη was recruited to Myc-induced RS sites, and Polη depletion enhanced the Myc-induced slowing and stalling of replication forks and the subsequent generation of double-strand breaks (DSBs). Overexpression of a catalytically dead Polη also promoted Myc-induced DSB formation. In the absence of Polη, Myc-induced DSB formation depended on MUS81-EME2 (the S-phase-specific endonuclease complex), and concomitant depletion of MUS81-EME2 and Polη enhanced RS and cell death in a synergistic manner. Collectively, these results indicate that Polη facilitates fork progression during Myc-induced RS, thereby helping cells tolerate the resultant deleterious effects. Additionally, the present study highlights the possibility of a synthetic sickness or lethality between Polη and MUS81-EME2 in cells experiencing Myc-induced RS.

ATR Inhibition Potentiates PARP Inhibitor Cytotoxicity in High Risk Neuroblastoma Cell Lines by Multiple Mechanisms

“…Although inhibiting ATR to specifically target RS in cancer cell looks promising, other mechanisms of tolerating RS have been identified, such as overexpression of components of the fork protection complex [66] and recruitment of Y-family (translesion synthesis) DNA polymerases [67,68], which should be considered as possible resistance mechanisms. These are all factors to be considered when interpreting data from the recently initiated trials of PARPi and ATRi combinations (NCT02723864, NCT03462342, NCT04065269, NCT03787680, NCT04149145, and NCT03682289).…”

Role of Y-family translesion DNA polymerases in replication stress: Implications for new cancer therapeutic targets

“…Both Pols Eta and Kappa have been shown to be involved in tolerance to different models of oncogene-induced replication stress. In one study by Kurashima et al [42], depletion of Pol Eta, and to a smaller extent Pol Kappa, led to cell cycle defects and a reduction in cell growth after inducing c-Myc overexpression. Focusing on Pol Eta for the rest of the study, the authors show that in a Rad18 and PCNA-Ub dependent manner, Pol Eta localizes to replication foci caused by c-Myc overexpression.…”

Chk1 loss creates replication barriers that compromise cell survival independently of excess origin firing

“…> 380 (track length) and > 600 (origin frequency) fibers obtained from 4 (track length) or 3 (origin frequency) independent experiments were measured for each condition. CDC45 excess provokes fork asymmetry (Srinivasan et al, 2013;Kohler et al, 2016) and Polg recruitment to replication foci (Kurashima et al, 2018); surplus CDC45 might therefore generate the obstacles that block the replisome in Chk1-depleted cells. Track lengths from > 290 fibers obtained from three independent experiments were measured for each condition.…”

“…This is intriguing since TLS prevents breaks at naturally occurring structured DNA (Betous et al, 2009) and enhances survival in cells displaying high CDK activity (Yang et al, 2017) or Myc-induced replication stress (Kurashima et al, 2018). Upon Chk1 loss, the difference between roscovitine and CDC45/MCM2 depletion is the quality, not the speed, of DNA elongation (with obstacles being bypassed by Polg and without obstacles, respectively).…”