DNA damage during S-phase mediates the proliferation-quiescence decision in the subsequent G1 via p21 expression.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28317845.
- Also identified by DOI 10.1038/ncomms14728 and PMC identifier 5364389.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Following DNA damage caused by exogenous sources, such as ionizing radiation, the tumour suppressor p53 mediates cell cycle arrest via expression of the CDK inhibitor, p21. However, the role of p21 in maintaining genomic stability in the absence of exogenous DNA-damaging agents is unclear. Here, using live single-cell measurements of p21 protein in proliferating cultures, we show that naturally occurring DNA damage incurred over S-phase causes p53-dependent accumulation of p21 during mother G2- and daughter G1-phases. High p21 levels mediate G1 arrest via CDK inhibition, yet lower levels have no impact on G1 progression, and the ubiquitin ligases CRL4<sup>Cdt2</sup> and SCF<sup>Skp2</sup> couple to degrade p21 prior to the G1/S transition. Mathematical modelling reveals that a bistable switch, created by CRL4<sup>Cdt2</sup>, promotes irreversible S-phase entry by keeping p21 levels low, preventing premature S-phase exit upon DNA damage. Thus, we characterize how p21 regulates the proliferation-quiescence decision to maintain genomic stability.
Medical subject headings
- Cell Proliferation
- Cyclin-Dependent Kinase Inhibitor p21
- DNA Damage
- G1 Phase
- S Phase