Induces CD27-mediated apoptosis. Inhibits BCL2L1 isoform Bcl-x(L) anti-apoptotic activity. Inhibits activation of NF-kappa-B and promotes T-cell receptor-mediated apoptosis. Isoform 1 binds 3 Zn(2+) ions. Isoform 2 binds 2 Zn(2+) ions. Binds through its N-terminal region to the C-terminus of CD27 and to PXMP2/PMP22. Binds to the C-terminus of TNFRSF18/GITR. Isoform 1 binds to BCL2L1/BCLX isoform Bcl-x(L) but not to BAX. (Microbial infection) Interacts with coxsackievirus B3 capsid protein VP2; this interaction inhibits the binding of SIVA1 to CD27. In the nucleus, accumulates in dot-like structures. Ubiquitous. Mostly expressed in thymus, testis, ovary, prostate, small intestine and spleen and less in colon. Phosphorylated by ABL2/ARG in response to oxidative stress. Could be used as a potentiator of cisplatin-based chemotherapy. Enhances cisplatin-mediated apoptosis, even under conditions where cisplatin resistance occurs due to elevated levels of BCL2 or BCL2L1. Mouse isoform 2 has been shown (PubMed:9177220) to have no pro-apoptotic activity. However, human isoform 2 has been shown to be capable of inducing apoptosis (PubMed:15034012).