Excessive transcription-replication conflicts are a vulnerability of BRCA1-mutant cancers

Nucleic Acids Res. 2023 May 22;51(9):4341-4362. doi: 10.1093/nar/gkad172.

Abstract

BRCA1 mutations are associated with increased breast and ovarian cancer risk. BRCA1-mutant tumors are high-grade, recurrent, and often become resistant to standard therapies. Herein, we performed a targeted CRISPR-Cas9 screen and identified MEPCE, a methylphosphate capping enzyme, as a synthetic lethal interactor of BRCA1. Mechanistically, we demonstrate that depletion of MEPCE in a BRCA1-deficient setting led to dysregulated RNA polymerase II (RNAPII) promoter-proximal pausing, R-loop accumulation, and replication stress, contributing to transcription-replication collisions. These collisions compromise genomic integrity resulting in loss of viability of BRCA1-deficient cells. We also extend these findings to another RNAPII-regulating factor, PAF1. This study identifies a new class of synthetic lethal partners of BRCA1 that exploit the RNAPII pausing regulation and highlight the untapped potential of transcription-replication collision-inducing factors as unique potential therapeutic targets for treating cancers associated with BRCA1 mutations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • BRCA1 Protein* / deficiency
  • BRCA1 Protein* / genetics
  • Cell Death
  • DNA Replication* / genetics
  • Hereditary Breast and Ovarian Cancer Syndrome* / genetics
  • Hereditary Breast and Ovarian Cancer Syndrome* / pathology
  • Hereditary Breast and Ovarian Cancer Syndrome* / physiopathology
  • Humans
  • Methyltransferases / deficiency
  • Methyltransferases / genetics
  • Mutation*
  • Promoter Regions, Genetic
  • R-Loop Structures
  • RNA Polymerase II / metabolism
  • Transcription, Genetic* / genetics

Substances

  • BRCA1 Protein
  • BRCA1 protein, human
  • PAF1 protein, human
  • RNA Polymerase II
  • MePCE protein, human
  • Methyltransferases