A Cancer-Associated Missense Mutation in PP2A-Aα Increases Centrosome Clustering during Mitosis.

Whole-genome doubling (WGD) is common early in tumorigenesis. WGD doubles ploidy and centrosome number. In the ensuing mitoses, excess centrosomes form a multipolar spindle, resulting in a lethal multipolar cell division. To survive, cells must cluster centrosomes to allow bipolar cell division. Cancer cells are often more proficient at centrosome clustering than untransformed cells, but the mechanism behind increased clustering ability is not well understood. Heterozygous missense mutations in PPP2R1A, which encodes the alpha isoform of the "scaffolding" subunit of PP2A (PP2A-Aα), positively correlate with WGD. We introduced a heterozygous hotspot mutation, P179R, into PPP2R1A in human RPE-1 cells. PP2A-Aα decreases PP2A assembly and intracellular targeting in mitosis. Strikingly, PP2A-Aα enhances centrosome clustering when centrosome number is increased either by cytokinesis failure or centrosome amplification, likely through PP2A-Aα loss of function. Thus cancer-associated mutations in PP2A-Aα may increase cellular fitness after WGD by enhancing centrosome clustering.