Expression of a murine homologue of the inhibitor of apoptosis protein is related to cell proliferation

The inhibitor of apoptosis (IAP) proteins form a highly conserved gene fami ly that prevents cell death in response to a variety of stimuli. Herein we describe a newly defined murine IAP, designated Tiap, that proved to be a m urine homologue of human survivin based on sequence comparison. TIAP has on e baculovirus IAP repeat and lacks a C-terminaI RING finger motif. TIAP int eracted with the processed form of caspase 3 and inhibited caspase-induced cell death. Histological examinations revealed that TIAP is expressed in gr owing tissues such as thymus, testis, and intestine of adult mice and many tissues of embryos. In in vitro studies, TIAP was induced in splenic T cell s activated with anti-CD3 antibody or Con A, and the expression of TIAP was up-regulated in synchronized NM 3T3 cells at S to G(2)/M phase of the cell cycle. We propose that during cell proliferation, cellular protective acti vity may be augmented with inducible IAPs such as TIAP.