title: CRL4(CDT2) targets CHK1 for PCNA-independent destruction.
abstract: CDT2 targets proteins involved in replication licensing (CDT1), cell cycle control (p21), and chromatin modification (SET8) for destruction by the CUL4-based E3 ligase (CRL4). CRL4(CDT2) recruits these substrates through interactions with chromatin-bound PCNA and ubiquitinates them exclusively on chromatin. Rereplication and G(2) cell cycle arrest are observed in CDT2-depleted cells. The rereplication phenotype has been attributed to an inability to destroy CDT1, but the molecular target important for G(2) cell cycle arrest in CDT2-depleted cells has not been identified. Here we identify CHK1 as a novel CRL4(CDT2) substrate and demonstrate that CHK1 activity is required for maintaining G(2) arrest in CDT2-depleted cells. We demonstrate that CRL4(CDT2) targets the activated form of CHK1 for destruction in the nucleoplasm rather than on chromatin and that this occurs in a PCNA-independent manner. Although both CRL1 and CRL4 ubiquitinate CHK1, we report that they bind CHK1 in distinct cellular compartments. Our study provides insight into how elevated CDT2 expression levels may provide tumors with a proliferative advantage.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Huh
authors.forename: Helen
authors.initials: H
authors.lastname: Piwnica-Worms
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002458:Cell Fractionation / Q000379:methods; D000071877:Checkpoint Kinase 1; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism*; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C467199:CDT1 protein, human; C488158:CLSPN protein, human; C114234:CUL4A protein, human; D018797:Cell Cycle Proteins; D002843:Chromatin; D044842:Cullin Proteins; C429530:DTL protein, human; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1