Anti-TOP1 binding arginine/serine rich protein, E3 ubiquitin ligase antibodies are used for the immunodetection of the protein encoded by the TOPORS gene. In humans, the canonical protein has a reported length of 1045 amino acid residues and a mass of 119.2 kDa. Its subcellular localization is in the nucleus. Alternative splicing is reported to yield 2 different isoforms for this protein. It is known to function as a E3 ubiquitin-protein ligase and as an E3 SUMO1-protein ligase. Post-translational modifications have been described, including ubiquitination, sumoylation and phosphorylation. The gene encoding this protein is implicated in Retinitis pigmentosa. Other names for this target antigen include P53BP3, RP31, TP53BPL, E3 ubiquitin-protein ligase Topors, RING-type E3 ubiquitin transferase Topors, and LUN. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.