Survivin (also known as baculoviral IAP repeat-containing protein (BIRC5)) is a member of the IAP family containing a BIR domain. This protein has two reported isoforms alpha and beta, with reported molecular weights of approximately 16.5 kD and 18.6 kD, respectively. Survivin can form dimers and is distributed at the microtubules of the mitotic spindle. Survivin plays a possible role in neoplasia and is expressed in embryonic tissues and the majority of human cancers, but not in most normal adult tissues. Survivin may counteract default induction of apoptosis in G2/M phase, and inhibits caspase-3 and caspase-7 activation. Survivin is downregulated by p53 and stabilized by phosphorylation. Survivin is phosphorylated by cdc2. Survivin has been shown to interact with tubulin and HBXIP. The Poly6147 antibody recognizes the C-terminal region of human survivin and has been shown to be useful for Western blotting.