In response to DNA damage, a cell can be forced to permanently exit the cell cycle and become senescent. Senescence provides an early barrier against tumor development by preventing proliferation of cells with damaged DNA. By studying single cells, we show that Cdk activity persists after DNA damage until terminal cell cycle exit. This low level of Cdk activity not only allows cell cycle progression, but also promotes cell cycle exit at a decision point in G2 phase. We find that residual Cdk1/2 activity is required for efficient p21 production, allowing for nuclear sequestration of Cyclin B1, subsequent APC/CCdh1 -dependent degradation of mitotic inducers and induction of senescence. We suggest that the same activity that triggers mitosis in an unperturbed cell cycle enforces senescence in the presence of DNA damage, ensuring a robust response when most needed.
- MeSH
- Single-Cell Analysis MeSH
- Cell Line MeSH
- Quinolines pharmacology MeSH
- Cyclin B1 genetics metabolism MeSH
- Cyclin-Dependent Kinase 2 antagonists & inhibitors genetics metabolism MeSH
- Epithelial Cells cytology drug effects enzymology MeSH
- Etoposide pharmacology MeSH
- Cyclin-Dependent Kinase Inhibitor p21 genetics metabolism MeSH
- Cadherins genetics metabolism MeSH
- G2 Phase Cell Cycle Checkpoints drug effects MeSH
- Humans MeSH
- Cell Line, Tumor MeSH
- Osteoblasts cytology drug effects enzymology MeSH
- DNA Damage MeSH
- CDC2 Protein Kinase antagonists & inhibitors genetics metabolism MeSH
- Pteridines pharmacology MeSH
- Purines pharmacology MeSH
- Gene Expression Regulation MeSH
- Retinal Pigment Epithelium cytology drug effects enzymology MeSH
- Signal Transduction MeSH
- Cellular Senescence drug effects MeSH
- Thiazoles pharmacology MeSH
- Cell Size MeSH
- Cell Survival drug effects MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Cdc7 kinase regulates DNA replication. However, its role in DNA repair and recombination is poorly understood. Here we describe a pathway that stabilizes the human Cdc7-ASK (activator of S-phase kinase; also called Dbf4), its regulation, and its function in cellular responses to compromised DNA replication. Stalled DNA replication evoked stabilization of the Cdc7-ASK (Dbf4) complex in a manner dependent on ATR-Chk1-mediated checkpoint signaling and its interplay with the anaphase-promoting complex/cyclosome(Cdh1) (APC/C(Cdh1)) ubiquitin ligase. Mechanistically, Chk1 kinase inactivates APC/C(Cdh1) through degradation of Cdh1 upon replication block, thereby stabilizing APC/C(Cdh1) substrates, including Cdc7-ASK (Dbf4). Furthermore, motif C of ASK (Dbf4) interacts with the N-terminal region of RAD18 ubiquitin ligase, and this interaction is required for chromatin binding of RAD18. Impaired interaction of ASK (Dbf4) with RAD18 disables foci formation by RAD18 and hinders chromatin loading of translesion DNA polymerase η. These findings define a novel mechanism that orchestrates replication checkpoint signaling and ubiquitin-proteasome machinery with the DNA damage bypass pathway to guard against replication collapse under conditions of replication stress.
- MeSH
- Ataxia Telangiectasia Mutated Proteins metabolism MeSH
- Genes, APC physiology MeSH
- HEK293 Cells MeSH
- HeLa Cells MeSH
- Cadherins metabolism MeSH
- Humans MeSH
- Cell Line, Tumor MeSH
- DNA Damage * MeSH
- Protein Serine-Threonine Kinases metabolism MeSH
- Protein Kinases metabolism MeSH
- Cell Cycle Proteins genetics metabolism MeSH
- DNA Replication * MeSH
- Signal Transduction MeSH
- Enzyme Stability MeSH
- Protein Binding MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
