Identification and Characterization of a Xenopus Homolog of Dbf4, a Regulatory Subunit of the Cdc7 Protein Kinase Required for the Initiation of DNA Replication

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概要

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• Dbf4 is a regulatory subunit for the Cdc7 protein kinase that is required for the initiation of eukaryotic DNA replication, but the precise roles of Dbf4-Cdc7 remain to be determined. Here we identified a Xenopus homolog of Dbf4 (XDbf4) and characterized XDbf4 and Xenopus Cdc7 (XCdc7) in Xenopus egg extracts. XDbf4 formed a complex with XCdc7 in egg extracts and activated XCdc7 kinase activity in vitro. In contrast with Dbf4 in yeast and mammalian cultured cells, the XDbf4 levels in egg extracts did not change during the cell cycle progression. XDbf4 was a phosphoprotein in interphase extracts, and was apparently hyperphosphorylated in cytostatic factor (CSF)-mediated, metaphase-arrested extracts and in mitotic extracts. However, the hyperphosphorylation of XDbf4 did not seem to affect the level of kinase activation, or chromatin binding of the XDbf4-XCdc7 complex. Upon release from CSF-arrest, XDbf4 was partially dephosphorylated and bound to chromatin. Interestingly, XDbf4 was loaded onto chromatin before XCdc7 during DNA replication in egg extracts. These results suggest that the function of XDbf4-XCdc7 during the early embryonic cell cycle is regulated in a manner distinct from that during the somatic cell cycle.

• 社団法人 日本生化学会の論文

著者

• Arai Ken-ichi

  Institute Of Medical Science University Of Tokyo

• Masai Hisao

  Tokyo Metropolitan Institute Of Medical Science

• Sugino Akio

  Research Institute For Microbial Diseases Osaka University

• Sato Noriko

  Institute Of Medical Science University Of Tokyo

• Waga Shou

  Research Institute For Microbial Diseases Graduate School Of Frontier Biosciences Osaka University

• Furukohri Asako

  Research Institute For Microbial Diseases Osaka University

関連論文

• REGULATION OF INITIATION AND PROGRESSION OF MAMMALIAN DNA REPLICATION WITH CDC7-RELATED KINASE COMPLEXES
• Identification and Characterization of a Xenopus Homolog of Dbf4, a Regulatory Subunit of the Cdc7 Protein Kinase Required for the Initiation of DNA Replication
• A Mouse Cdc7/Homologue of H37 Complex : Targeted deletion of the murine Cdc7 gene cause early embryomic lethality.
• Regulation of chromosomal replication by growth factors : CDC7-related kinase, a key regulator of initiation of the S phase
• Accumulation of FFA-1, the Xenopus Homolog of Werner Helicase, and DNA Polymerase δ on Chromatin in Response to Replication Fork Arrest
• Identification and Characterization of a Xenopus Homolog of Dbf4, a Regulatory Subunit of the Cdc7 Protein Kinase Required for the Initiation of DNA Replication

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