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 (By similarity). 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. Interacts with the androgen receptor AR. Interacts with IQGAP1 and PPM1B (By similarity). Cotranslocates into nucleus with AR in response to androgen induction. Autophosphorylated. Phosphorylated by MAP2K6/MAPKK6, leading to PAK6 activation (By similarity). Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. STE20 subfamily.