RNA Binding Motif Protein 15B (RBM15B)

RBM15B shares 58% and 30% amino acid identity with RBM15 and human SPEN over the SPOC domain. Northern blot analysis of human tissues detected strong expression of a 3.5-kb transcripts in heart, placenta, brain, kidney, and thymus with moderate expression in peripheral blood leukocytes, lung, small intestine, liver, spleen, colon, and muscle. A longer 7.5-kb transcript was detected with weak expression in all tissues examined. Western blot analysis of epithelial cells and EBV-positive Burkitt lymphoma cells detected RBM15B as a 120-kD species. Confocal microscopy colocalized RBM15B and EB2 to the nucleus in a granular staining pattern excluded from the nucleolus. Heterokaryon analysis demonstrated that, unlike EB2, RBM15B was not a shuttling protein and displayed restricted localization to the nucleus even in the presence of EB2.