Activating signal cointegrator 1 is a protein that in humans is encoded by the TRIP4 gene. Transcription coactivator of nuclear receptors which functions in conjunction with CBP-p300 and SRC-1 and may play an important role in establishing distinct coactivator complexes under different cellular conditions. Plays a pivotal role in the transactivation of NF-kappa-B, SRF and AP1. Acts as a mediator of transrepression between nuclear receptor and either AP1 or NF-kappa-B. Plays a role in androgen receptor transactivation and in testicular function (By similarity).