Serine/threonine-protein kinase 4 (STK4)

Stress-activated, pro-apoptotic kinase which, following caspase-cleavage, enters the nucleus and causes chromatin condensation followed by internucleosomal DNA fragmentation. Key part of the Hippo signaling pathway which plays a pivotal role in organ size control and tumor suppression by restricting proliferation and promoting apoptosis.

The crux of this pathway is made up of a kinase cascade wherein STK3/MST2 and STK4/MST1, in complex with its regulatory protein SAV1, phosphorylates and activates LATS1/2 in complex with its regulatory protein MOB1, which then phosphorylates and inactivates YAP1 oncoprotein and WWTR1/TAZ. Phosphorylation of YAP1 by LATS2 inhibits its translocation to the nucleus to regulate cellular genes important for cell proliferation, cell death, and cell migration.