Synaptotagmin Interacting Protein (SIP)

The deduced 669-amino acid protein has a calculated molecular mass of 69 kD. It has 2 N-terminal RNA recognition motifs (RRMs), each of which includes the conserved RNP1 and RNP2 motifs, and a C-terminal TRBP (TARBP2)-interacting domain that contains over 20 copies of the motif xYxxQ, in which x is a small amino acid. The deduced 156-amino acid COAM protein has a calculated molecular mass of 17 kD. The first 150 amino acids of COAM and COAA are identical, but COAM lacks the C-terminal TRBP-binding domain. COAA, but not COAM, interacted with the C-terminal domains of TRBP and p300 (EP300). In reporter gene assays, COAA acted as a general coactivator on multiple hormone response elements, and it acted synergistically with TRBP and CREB-binding protein (CREBBP).