Lebrec V, Poteau M, Morretton JP, Gavet O. Chk1 dynamics in G2 phase upon replication stress predict daughter cell outcome.
Dev Cell 2022;
57:638-653.e5. [PMID:
35245445 DOI:
10.1016/j.devcel.2022.02.013]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 12/16/2021] [Accepted: 02/08/2022] [Indexed: 12/27/2022]
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.
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