Cyclin D1-mediated inhibition of repair and replicative DNA synthesis in human fibroblasts.
Cyclin D1 is a key regulator of the G1 phase of the cell cycle. Inhibition of cyclin D1 function results in cell cycle arrest, whereas unregulated expression of the protein accelerates G1. Cyclin D1 is localized to the nucleus during G1. We found that during repair DNA synthesis, subsequent to UV-induced DNA damage, G1 cells readily lost their cyclin D1 while the proliferating cell nuclear antigen (PCNA) tightly associated with nuclear structures. Microinjection of cyclin D1 antisense accelerated DNA repair, whereas overexpression of cyclin D1 prevented DNA repair and the relocation of PCNA after DNA damage. Coexpression of cyclin D1 with its primary catalytic subunit, Cdk4, or with Cdk2, also prevented repair. In contrast, coexpression of PCNA, which is also a cyclin D1-associated protein, restored the ability of cells to repair their DNA. Acute overexpression of cyclin D1 in fibroblasts prevented them from entering S phase. Again, these effects were abolished by coexpression of cyclin D1 together with PCNA, but not with Cdk4 or Cdk2. Altogether, these results indicate that down-regulation of cyclin D1 is necessary for PCNA relocation and repair DNA synthesis as well as for the start of DNA replication. Cyclin D1 appears to be an essential component of a G1-checkpoint.
Mitotix Incorporated, Cambridge, Massachusetts 02139.
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Theodoras
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Draetta
D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle; D002460:Cell Line; D002461:Cell Line, Transformed; D019938:Cyclin D1; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis; D016213:Cyclins / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D008168:Lung; D015513:Oncogene Proteins / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D010957:Plasmids; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis; D011518:Proto-Oncogene Proteins; D014162:Transfection; D014466:Ultraviolet Rays
D016213:Cyclins; D015513:Oncogene Proteins; D018809:Proliferating Cell Nuclear Antigen; D011518:Proto-Oncogene Proteins; D019938:Cyclin D1; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases