Three important nuclear receptor coactivators that display HAT activity are SRC-1, ACTR, and TIF-2. Human SRC-1 (steroid receptor coactivator-1) is known to interact with p300/CBP and PCAF, and its HAT domain is located in its C-terminal region. ACTR (also known as RAC3, AIB1, and TRAM-1 in humans) shares significant sequence homology with SRC-1, in particular in the N-terminal and C-terminal (HAT) regions as well as in the receptor and coactivator interaction domains. ACTR also interacts with p300/CBP and PCAF. The former can prevent ACTR from binding to and activating its receptor by acetylating it in its receptor interaction domain. TIF-2 (transcriptional intermediary factor 2; also known as GRIP1) is another nuclear receptor coactivator with HAT activity, and it also interacts with p300/CBP.