1. Academic Validation
  2. Chk1 dynamics in G2 phase upon replication stress predict daughter cell outcome

Chk1 dynamics in G2 phase upon replication stress predict daughter cell outcome

  • Dev Cell. 2022 Mar 14;57(5):638-653.e5. doi: 10.1016/j.devcel.2022.02.013.
Vicente Lebrec 1 Marion Poteau 1 Jean-Philippe Morretton 1 Olivier Gavet 2
Affiliations

Affiliations

  • 1 UMR9019 CNRS, Université Paris-Saclay, Gustave Roussy Cancer Campus, 94805 Villejuif Cedex, France.
  • 2 Sorbonne Universités, UPMC Paris VI, UFR927, 75005 Paris, France; UMR9019 CNRS, Université Paris-Saclay, Gustave Roussy Cancer Campus, 94805 Villejuif Cedex, France. Electronic address: olivier.gavet@gustaveroussy.fr.
Abstract

In human cells, ATR/Chk1 signaling couples S phase exit with the expression of mitotic inducers and prevents premature mitosis upon replication stress (RS). Nonetheless, under-replicated DNA can persist at mitosis, prompting chromosomal instability. To decipher how the DNA replication checkpoint (DRC) allows cells to enter mitosis over time upon RS, we developed a FRET-based Chk1 activity sensor. During unperturbed growth, a basal Chk1 activity level is sustained throughout S phase and relies on replication origin firing. Incremental RS triggers stepwise Chk1 over-activation that delays S-phase, suggesting a rheostat-like role for DRC coupled with the replication machinery. Upon RS, Chk1 is inactivated as DNA replication terminates but surprisingly is reactivated in a subset of G2 cells, which relies on CDK1/2 and PLK1 and prevents mitotic entry. Cells can override active Chk1 signaling and reach mitosis onset, revealing checkpoint adaptation. Cell division following Chk1 reactivation in G2 results in a p53/p21-dependent G1 arrest, eliminating the daughter cells from proliferation.

Keywords

DNA replication checkpoint; FRET biosensor; G2 phase; cell cycle recovery; checkpoint adaptation; checkpoint kinase 1; replication stress.

Figures
Products