Progression into M phase is dependent on cyclin Bdependent kinase activity, CycB–Cdk1, also called M phase-promoting factor (MPF). Before undergoing chromosome condensation and nuclear division, cells have to be sure that their DNA is fully replicated and undamaged. If not, the cell is delayed in S–G2 by Wee1-induced phosphorylation of tyrosine and threonine residues of the catalytic subunit of MPF. (The phosphorylated dimer is called preMPF.) The G2!M transition is brought about by rapid conversion of preMPF to MPF, catalysed by Cdc25C. Hence, the obvious targets of the G2 checkpoint are the positive feedback loops controlling the activity of
CycB–Cdk1 (MPF activates Cdc25C and inhibits Wee1).
Progression into M phase is dependent on cyclin Bdependent kinase activity, CycB–Cdk1, also called M phase-promoting factor (MPF). Before undergoing chromosome condensation and nuclear division, cells have to be sure that their DNA is fully replicated and undamaged. If not, the cell is delayed in S–G2 by Wee1-induced phosphorylation of tyrosine and threonine residues of the catalytic subunit of MPF. (The phosphorylated dimer is called preMPF.) The G2!M transition is brought about by rapid conversion of preMPF to MPF, catalysed by Cdc25C. Hence, the obvious targets of the G2 checkpoint are the positive feedback loops controlling the activity ofCycB–Cdk1 (MPF activates Cdc25C and inhibits Wee1).
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