Serine/threonine protein kinase that plays a role in the regulation of gene transcription. The kinase activity is induced by various effectors including AR or MAP2K6/MAPKK6. Phosphorylates the DNA-binding domain of androgen receptor/AR and thereby inhibits AR-mediated transcription. Inhibits also ESR1-mediated transcription. May play a role in cytoskeleton regulation by interacting with IQGAP1. May protect cells from apoptosis through phosphorylation of BAD. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts tightly with GTP-bound but not GDP-bound CDC42/p21 and RAC1 (By similarity). Interacts with the androgen receptor AR and the estrogen receptor ESR1. Interacts with IQGAP1 and PPM1B. Cotranslocates into nucleus with AR in response to androgen induction. Selectively expressed in brain and testis, with lower levels in multiple tissues including prostate and breast. Autophosphorylated. Phosphorylated by MAP2K6//MAPKK6, leading to PAK6 activation. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. STE20 subfamily.