title: In vivo association of Ku with mammalian origins of DNA replication.
abstract: Ku is a heterodimeric (Ku70/86-kDa) nuclear protein with known functions in DNA repair, V(D)J recombination, and DNA replication. Here, the in vivo association of Ku with mammalian origins of DNA replication was analyzed by studying its association with ors8 and ors12, as assayed by formaldehyde cross-linking, followed by immunoprecipitation and quantitative polymerase chain reaction analysis. The association of Ku with ors8 and ors12 was also analyzed as a function of the cell cycle. This association was found to be approximately fivefold higher in cells synchronized at the G1/S border, in comparison with cells at G0, and it decreased by approximately twofold upon entry of the cells into S phase, and to near background levels in cells at G2/M phase. In addition, in vitro DNA replication experiments were performed with the use of extracts from Ku80(+/+) and Ku80(-/-) mouse embryonic fibroblasts. A decrease of approximately 70% in in vitro DNA replication was observed when the Ku80(-/-) extracts were used, compared with the Ku80(+/+) extracts. The results indicate a novel function for Ku as an origin binding-protein, which acts at the initiation step of DNA replication and dissociates after origin firing.
authors.affiliation: McGill Cancer Center, McGill University, Montreal, Quebec, Canada H3G 1Y6.
authors.forename: O
authors.initials: O
authors.lastname: Novac
authors.forename: D
authors.initials: D
authors.lastname: Matheos
authors.forename: F D
authors.initials: FD
authors.lastname: Araujo
authors.forename: G B
authors.initials: GB
authors.lastname: Price
authors.forename: M
authors.initials: M
authors.lastname: Zannis-Hadjopoulos
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear; D001665:Binding Sites; D002453:Cell Cycle; D002457:Cell Extracts; D002460:Cell Line; D003432:Cross-Linking Reagents; D004265:DNA Helicases; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005557:Formaldehyde; D000072200:Ku Autoantigen; D008322:Mammals; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D011233:Precipitin Tests; D018741:Replication Origin; D012261:Ribonucleoproteins; D000068103:Serine-Arginine Splicing Factors; D051996:Transcription Factor RelA
chemical_list: D034961:Antigens, Nuclear; D002457:Cell Extracts; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D012261:Ribonucleoproteins; C499372:SRSF2 protein, mouse; D051996:Transcription Factor RelA; D000068103:Serine-Arginine Splicing Factors; D005557:Formaldehyde; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen