P53 orchestrates DNA replication restart homeostasis by suppressing mutagenic RAD52 and POLθ pathways.

Sunetra Roy,Karl-Heinz Tomaszowski,Jun Li,Soyoung Park,Maureen Murphy,Jessica W Luzwick,Katharina Schlacher

doi:10.7554/elife.31723

Sunetra Roy, Karl-Heinz Tomaszowski + Show 5 more

Open Access

https://doi.org/10.7554/elife.31723

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Abstract

Classically, p53 tumor suppressor acts in transcription, apoptosis, and cell cycle arrest. Yet, replication-mediated genomic instability is integral to oncogenesis, and p53 mutations promote tumor progression and drug-resistance. By delineating human and murine separation-of-function p53 alleles, we find that p53 null and gain-of-function (GOF) mutations exhibit defects in restart of stalled or damaged DNA replication forks that drive genomic instability, which isgenetically separable from transcription activation. By assaying protein-DNA fork interactions in single cells, we unveil a p53-MLL3-enabled recruitment of MRE11 DNA replication restart nuclease. Importantly, p53 defects or depletion unexpectedly allow mutagenic RAD52 and POLθ pathways to hijack stalled forks, which we find reflected in p53 defective breast-cancer patient COSMIC mutational signatures. These data uncover p53 as a keystone regulator of replication homeostasis within a DNA restart network. Mechanistically, this has important implications for development of resistance in cancer therapy. Combined, these results define an unexpected role for p53-mediated suppression of replication genome instability.

Highlights

One of the most prominent hallmarks of cancer is genomic instability (Hanahan and Weinberg, 2011)
Utilization of mutagenic RAD52/ POLq replication pathways increase for both GOF and p53 null alleles in a transcription independent manner, consistent with mutation signatures that we identify in p53 mutant breast cancers
As BLM helicase is implicated in replication restart (Davies et al, 2007), as is ATM (Trenz et al, 2006), we tested the role of p53 in DNA replication reactions when stalled with dNTP depleting hydroxyurea (HU)

Summary

Introduction

One of the most prominent hallmarks of cancer is genomic instability (Hanahan and Weinberg, 2011). As previously hypothesized (Cox et al, 2000), recent findings formalized that 2/3 of all mutations found across cancers are caused by errors occurring during proliferation (Tomasetti et al, 2017), highlighting the critical importance of protective mechanisms during DNA replication. Utilization of mutagenic RAD52/ POLq replication pathways increase for both GOF and p53 null alleles in a transcription independent manner, consistent with mutation signatures that we identify in p53 mutant breast cancers. Our results allow for an unexpected alternative hypothesis for acquisition of drug resistance in breast cancer cells due to p53 loss: mutant p53 boosts mutagenic RAD52/POLq pathways, which increase deletion and point mutations that can lead to secondary resistance mutations

Results

Discussion

Materials and methods