The HS-1 associated protein X-1 (Hax1) was initially identified in a yeast two-hybrid assay on the basis of its ability to bind to the hemapoietic cell-specific protein 1 (HS-1). Hax1 possesses anti-apoptotic activity and is structurally related to Bcl-2 family members, including the presence of BH1- and BH2-like domains. It has recently been shown to interact with HIV viral protein R (Vpr), a protein required for viral pathogenesis of HIV and linked to T-cell apoptosis through activation of caspases 3 and 9. Other studies indicate that Hax1-mediated processing of HtrA2 (also known as Omi) by the mitochondrial protease PARL allows survival of lymphocytes and neurons when cytokines are limiting. At least four isoforms of Hax1 are known to exist. This antibody is expected to recognize the longest isoform (Hax1a) as well as the shortest.
