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Updated: Aug 30, 2026

Quantitative Detection of DNA-Protein Crosslinks and Their Post-Translational Modifications
Published on: April 21, 2023
Radiation-mediated proteolysis of CDT1 by CUL4-ROC1 and CSN complexes constitutes a new checkpoint
Leigh Ann A Higa1, Ivailo S Mihaylov, Damon P Banks
1Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
Abstract:
Genomic integrity is maintained by checkpoints that guard against undesired replication after DNA damage. Here, we show that CDT1, a licensing factor of the pre-replication complex (preRC), is rapidly proteolysed after UV- or gamma-irradiation. The preRC assembles on replication origins at the end of mitosis and during G1 to license DNA for replication in S phase. Once the origin recognition complex (ORC) binds to origins, CDC6 and CDT1 associate with ORC and promote loading of the MCM2-7 proteins onto chromatin, generating the preRC. We show that radiation-mediated CDT1 proteolysis is independent of ATM and CHK2 and can occur in G1-phase cells. Loss of the COP9-signalosome (CSN) or CUL4-ROC1 complexes completely suppresses CDT1 proteolysis. CDT1 is specifically polyubiquitinated by CUL4 complexes and the interaction between CDT1 and CUL4 is regulated in part by gamma-irradiation. Our study reveals an evolutionarily conserved and uncharacterized G1 checkpoint that induces CDT1 proteolysis by the CUL4-ROC1 ubiquitin E3 ligase and CSN complexes in response to DNA damage.
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