Supplementary Methods from Identification of a Protein, G0S2, That Lacks Bcl-2 Homology Domains and Interacts with and Antagonizes Bcl-2
ARTICLE ABSTRACT
The Bcl-2 family of proteins consists of both antiapoptotic and proapoptotic factors, which share sequence homology within conserved regions known as Bcl-2 homology domains. Interactions between Bcl-2 family members, as well as with other proteins, regulate apoptosis through control of mitochondrial membrane permeability and release of cytochrome c. Here we identify a novel regulator of apoptosis that lacks Bcl-2 homology domains but acts by binding Bcl-2 and modulating its antiapoptotic activity. To identify regulators of apoptosis, we performed expression profiling in human primary fibroblasts treated with tumor necrosis factor-α (TNF-α), a potent inflammatory cytokine that can regulate apoptosis and functions, at least in part, by inducing expression of specific genes through NF-κB. We found that the gene undergoing maximal transcriptional induction following TNF-α treatment was G0-G1 switch gene 2 (G0S2), the activation of which also required NF-κB. We show that G0S2 encodes a mitochondrial protein that specifically interacts with Bcl-2 and promotes apoptosis by preventing the formation of protective Bcl-2/Bax heterodimers. We further show that ectopic expression of G0S2 induces apoptosis in diverse human cancer cell lines in which endogenous G0S2 is normally epigenetically silenced. Our results reveal a novel proapoptotic factor that is induced by TNF-α through NF-κB and that interacts with and antagonizes Bcl-2. [Cancer Res 2009;69(17):6782–9]
