CONTROL OF DNA-REPLICATION BY PROTEIN-PHOSPHORYLATION

Protein phosphorylation is a versatile posttranslational modification and the most eminent molecular mechanism that can regulate enzymatic a ctivities, emergence of cells from quiescence, DNA replication and ons et of mitosis, gene expression, nuclear import, development and memory . The cell cycle is mainly regulated by p34(cdc2) in association with cyclins B at G2/M and by Cdk2 in association with cyclins A, D1, and E at G1/S checkpoints. MAP kinases might link the Go to GI transition w ith the regulation of the cell cycle whereas phosphorylation of replic ation protein factors, c-Myc, AP-1, Oct-1, T-antigen, retinoblastoma, and p53 might link the G1 to S transition with the control of DNA synt hesis. These transcription regulators can up- or downregulate DNA repl ication and their DNA binding activities or transacting properties are controlled by phosphorylation.