Radiation-mediated proteolysis of CDT1 by CUL4-ROC1 and CSN complexes constitutes a new checkpoint.
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.
Higa
Leigh Ann A
LA
Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
Mihaylov
Ivailo S
IS
Banks
Damon P
DP
Zheng
Jianyu
J
Zhang
Hui
H
D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000528:radiation effects*; D002460:Cell Line; D004261:DNA Replication; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data
D018797:Cell Cycle Proteins