Anti-UPF3B regulator of nonsense mediated mRNA decay antibodies are used for the immunodetection of the protein encoded by the UPF3B gene. In humans, the canonical protein has a reported length of 483 amino acid residues and a mass of 57.8 kDa. Its subcellular localization is in the nucleus and cytoplasm. Alternative splicing is reported to yield 2 different isoforms for this protein. It is reported to be expressed in the testis, uterus, prostate, heart, muscle, brain, spinal cord and placenta. A member of the RENT3 protein family, it is known to be involved in nonsense-mediated decay (NMD) of mRNAs containing premature stop codons by associating with the nuclear exon junction complex (EJC) and serving as link between the EJC core and NMD machinery. Other names for this target antigen include UPF3 regulator of nonsense transcripts homolog B, UPF3B pseudogene 1, UPF3B pseudogene 2, UPF3B pseudogene 3, and regulator of nonsense transcripts 3B. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.