Radiation-mediated proteolysis of CDT1 by CUL4-ROC1 and CSN complexes constitutes a new checkpoint

• Published in: Nature cell biology Vol. 5; no. 11; pp. 1008 - 1015
• Main Authors: Zhang, Hui, Higa, Leigh Ann A, Mihaylov, Ivailo S, Banks, Damon P, Zheng, Jianyu
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.11.2003
• Subjects: CDT1 protein; Cell Cycle; Cell Cycle Proteins - metabolism; Cell Cycle Proteins - radiation effects; Cell division; Cell Line; CUL4 protein; DNA binding proteins; DNA damage; DNA Replication; Genetic aspects; Genetic research; Humans; Hydrolysis; Insects; Irradiation (Radiation exposure); Kinases; Licenses; Ligases; Molecular Sequence Data; Physiological aspects; Proteins; Proteolysis; Radiation; ROC1 protein; Ubiquitin-proteasome system; Yeast; United States
• ISSN: 1465-7392; 1476-4679; 1476-4679
• DOI: 10.1038/ncb1061

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 γ-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 γ-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.