PIASy interacts with p73α and regulates cell cycle in HEK293 cells

p73, a recently described member of the p53 family of transcription factors, undergoes a number of posttranslational modifications, inducing cell cycle arrest and apoptosis. In the present study, we demonstrate that PIASy, a member of the PIAS SUMO-ligase family, interacts with p73α, and that PIASy-mediated sumoylation promotes proteasomal degradation of p73α. PIASy overexpression inhibits p73α-mediated transcription of p21, with a reduction of cells in G1 and cell cycle reentry. These results suggest that PIASy plays an important role in regulation of p73α transcriptional activity and is also a regulator of the cell cycle machinery.