TRIM36 (tripartite motif-containing 36), also known as RNF98 (RING finger protein 98), HAPRIN (haploid germ cell-specific RBCC protein) or RBCC728, is a 728 amino acid protein that belongs to the TRIM/RBCC (Ring finger, B box, coiled-coil) family. Predominantly expressed in prostate, testis and brain with weak expression in heart, kidney and lung, TRIM36 contains two B box-type zinc fingers, a SPRY domain, a coiled-coil domain, a fibronectin type-III domain and a RING-type zinc finger; a motif that has zinc-chelating activity and is involved in mediating protein-protein and protein-DNA interactions. Localizing to the cytoplasm and the acrosomal region of germ cells and mature sperm, TRIM36 is believed to play a role in the acrosome reaction and fertilization. In addition, TRIM36 is overexpressed in prostate cancer, suggesting a possible role for TRIM36 in prostate tumorigenesis.