T-Cell Restricted Intracellular Antigen 1 (TIA1)

TIA1 is a member of a RNA-binding protein family and possesses nucleolytic activity against cytotoxic lymphocyte (CTL) target cells. It has been suggested that this protein may be involved in the induction of apoptosis as it preferentially recognizes poly(A) homopolymers and induces DNA fragmentation in CTL targets. The major granule-associated species is a 15-kDa protein that is thought to be derived from the carboxyl terminus of the 40-kDa product by proteolytic processing. Although they identified the transcription start site of the mRNA encoding the 40-kD TIA1 protein, they could not identify a second promoter capable of initiating an mRNA encoding the 15-kD TIA1 protein. This supports the possibility that the 15-kD isoform is derived from the 40-kD isoform by proteolysis.