Anti-U3-55K antibodies enable researchers to detect and measure the U3-55K antigen in biological samples. This target is a reported synonym of the RRP9 gene, which encodes ribosomal RNA processing 9, U3 small nucleolar RNA binding protein. This protein is known to function in rRNA processing, among other biological roles. The human version of U3-55K has a canonical amino acid length of 475 residues and a protein mass of 51.8 kilodaltons. It is reported to be localized in the nucleus of cells. U3-55K is a member of the WD repeat RRP9 protein family.