ELK4, also named as SAP1, SAP-1 and SAP1, belongs to the ETS family. It forms a ternary complex with the serum response factor (SRF). ELK4 requires DNA-bound SRF for ternary complex formation and makes extensive DNA contacts to the 5'side of SRF, but does not bind DNA autonomously. It is androgen regulated, involved in promoting cell growth.