Abstract
Cdc7, a protein kinase required for the initiation of eukaryotic DNA replication, is activated by a regulatory subunit, Dbf4. A second activator of Cdc7 called Drf1 exists in vertebrates, but its function is unknown. Here, we report that in Xenopus egg extracts, Cdc7-Drf1 is far more abundant than Cdc7-Dbf4, and removal of Drf1 but not Dbf4 severely inhibits phosphorylation of Mcm4 and DNA replication. After gastrulation, when the cell cycle acquires somatic characteristics, Drf1 levels decline sharply and Cdc7-Dbf4 becomes the more abundant kinase. These results identify Drf1 as a developmentally regulated, essential activator of Cdc7 in Xenopus.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / metabolism*
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Animals
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cell-Free System / metabolism
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Chromosomal Proteins, Non-Histone / genetics
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Chromosomal Proteins, Non-Histone / metabolism*
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DNA Replication / physiology*
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Female
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Gastrula / metabolism*
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Gene Expression Regulation, Developmental / physiology
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Oocytes / physiology
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Xenopus
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Xenopus Proteins / genetics
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Xenopus Proteins / metabolism*
Substances
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Adaptor Proteins, Signal Transducing
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Cell Cycle Proteins
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Chromosomal Proteins, Non-Histone
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DBF4B protein, Xenopus
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Dbf4 protein, Xenopus
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Xenopus Proteins
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CDC7 protein, Xenopus
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Protein Serine-Threonine Kinases