Requirement of Cyclin/Cdk2 and protein phosphatase 1 activity for chromatin assembly factor 1-dependent chromatin assembly during DNA synthesis.
The influence of reversible protein phosphorylation on nucleosome assembly during DNA replication was analyzed in extracts from human cells. Inhibitor studies and add-back experiments indicated requirements of cyclin A/Cdk2, cyclin E/Cdk2, and protein phosphatase type 1 ( PP1) activities for nucleosome assembly during DNA synthesis by chromatin assembly factor 1 ( CAF-1). The p60 subunit of CAF-1 is a molecular target for reversible phosphorylation by cyclin/Cdk complexes and PP1 during nucleosome assembly and DNA synthesis in vitro. Purified p60 can be directly phosphorylated by purified cyclin A/Cdk2, cyclin E/Cdk2, and cyclin B1/Cdk1, but not by cyclin D/Cdk4 complexes in vitro. Cyclin B1/Cdk1 triggers hyperphosphorylation of p60 in the presence of additional cytosolic factors. CAF-1 containing hyperphosphorylated p60 prepared from mitotic cells is inactive in nucleosome assembly and becomes activated by dephosphorylation in vitro. These data provide functional evidence for a requirement of the cell cycle machinery for nucleosome assembly by CAF-1 during DNA replication.[1]References
- Requirement of Cyclin/Cdk2 and protein phosphatase 1 activity for chromatin assembly factor 1-dependent chromatin assembly during DNA synthesis. Keller, C., Krude, T. J. Biol. Chem. (2000) [Pubmed]
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