title: The role of Dbf4/Drf1-dependent kinase Cdc7 in DNA-damage checkpoint control.
abstract: The Dbf4/Drf1-dependent S-phase-promoting kinase Cdc7 (Ddk) is thought to be an essential target inactivated by the S-phase checkpoint machinery that inhibits DNA replication. However, we show here that the complex formation, chromatin association, and kinase activity of Ddk are not inhibited during the DNA-damage-induced S-phase checkpoint response in Xenopus egg extracts and mammalian cells. Instead, we find that Ddk plays an active role in regulating S-phase checkpoint signaling. Addition of purified Ddk to Xenopus egg extracts or overexpression of Dbf4 in HeLa cells downregulates ATR-Chk1 checkpoint signaling and overrides the inhibition of DNA replication and cell-cycle progression induced by DNA-damaging agents. These results indicate that Ddk functions as an upstream regulator to monitor S-phase checkpoint signaling. We propose that Ddk modulates the S-phase checkpoint control by attenuating checkpoint signaling and triggering DNA replication reinitiation during the S-phase checkpoint recovery.
authors.affiliation: The Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Toshiya
authors.initials: T
authors.lastname: Tsuji
authors.forename: Eric
authors.initials: E
authors.lastname: Lau
authors.forename: Gary G
authors.initials: GG
authors.lastname: Chiang
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002457:Cell Extracts; D000071877:Checkpoint Kinase 1; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004249:DNA Damage; D015536:Down-Regulation / Q000187:drug effects; D005047:Etoposide / Q000494:pharmacology; D000080865:Formins; D006367:HeLa Cells; D006801:Humans; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014981:Xenopus; D029867:Xenopus Proteins / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D002457:Cell Extracts; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; C485678:DBF4 protein, human; C505573:DBF4B protein, Xenopus; C108962:DIAPH1 protein, human; C505572:Dbf4 protein, Xenopus; D000080865:Formins; D029867:Xenopus Proteins; D005047:Etoposide; D011494:Protein Kinases; C489405:CDC7 protein, Xenopus; C068619:CDC7 protein, human; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605875:Chek1 protein, Xenopus; D017346:Protein Serine-Threonine Kinases