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PubMed2002

14-3-3s are DNA-replication proteins.

14-3-3 proteins are conserved multifunctional molecules, involved in many biological processes. Several 14-3-3 isoforms were recently shown to be cruciform DNA-binding proteins, which is a new activity ascribed to the 14-3-3 family. As cruciform-binding proteins, 14-3-3 proteins are putatively involved in the regulation of DNA replication. Inverted repeat sequences that are able to extrude into cruciform structures are a common feature of replication origins in both prokaryotes and eukaryotes. The involvement of cruciform structures in the initiation of DNA replication has been demonstrated. A leading model of 14-3-3 function proposes that they facilitate critical protein-protein interactions, thus serving as a central component of a wide variety of cellular processes.

14-3-3 Proteins↗

PubMed2001

In vivo association of Ku with mammalian origins of DNA replication.

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.

Animals↗