Gain of function properties of mutant p53 proteins at the mitotic spindle cell cycle checkpoint.

Mutations in the p53 tumor suppressor gene locus predispose human cells to chromosomal instability. This is due in part to interference of mutant p53 proteins with the activity of the mitotic spindle and postmitotic cell cycle checkpoints. Recent data demonstrates that wild type p53 is required for postmitotic checkpoint activity, but plays no role at the mitotic spindle checkpoint. Likewise, structural dominant p53 mutants demonstrate gain-of-function properties at the mitotic spindle checkpoint and dominant negative properties at the postmitotic checkpoint. At mitosis, mutant p53 proteins interfere with the control of the metaphase-to-anaphase progression by up-regulating the expression of CKs1, a protein that mediates activatory phosphorylation of the anaphase promoting complex (APC) by Cdc2. Cells that carry mutant p53 proteins overexpress CKs1 and are unable to sustain APC inactivation and mitotic arrest. Thus, mutant p53 gain-of-function at mitosis constitutes a key component to the origin of chromosomal instability in mutant p53 cells.