Regulation of survivin stability by the aryl hydrocarbon receptor-interacting protein

Survivin is a multifunctional member of the IAP ( inhibitor of apoptosis) family, but its molecular interactions in protection from cell death and regulation of cell division have not been completely elucidated. In a proteomics screening to identify novel survivin-binding partners, we found that the aryl hydrocarbon receptor-interacting protein (AIP) directly associates with survivin in vitro and in co-immunoprecipitation experiments in vivo. This interaction is mediated by the carboxyl-terminal end of AIP, which contains three tetratricopeptide motifs, and involves the carboxyl terminus coiled coil in survivin with critical roles of Asp142 in AIP recognition. A survivin mutant lacking only Asp142 fails to bind AIP and exhibits accelerated degradation in vivo in a reaction reversed by a proteasome inhibitor. Acute knock-down of AIP by short interference RNA or competition of the survivin AIP complex by peptidyl mimicry destabilizes survivin levels in cells, with enhanced apoptosis but no changes in cell cycle progression. Therefore, AIP regulates survivin stability, thus elevating a cellular anti-apoptotic threshold. The survivin-AIP complex may influence the cellular xenobiotic response to environmental toxin(s) and contribute to subcellular chaperone trafficking during cell death regulation.