WW Domain Binding Protein 4 (WBP4)

WBP4 encodes WW domain-containing binding protein 4. The WW domain represents a small and compact globular structure that interacts with proline-rich ligands. This encoded protein is a general spliceosomal protein that may play a role in cross-intron bridging of U1 and U2 snRNPs in the spliceosomal complex A.The predicted 376-amino acid FBP21 protein contains an N-terminal zinc finger motif and 2 WW domains. Western blot analysis of in vitro translated FBP21 protein and of HeLa cell extracts showed that FBP21 migrates as a 58-kD polypeptide. Immunofluorescence studies of HeLa cells indicated that endogenous FBP21 is exclusively localized to the nucleus and concentrated in a punctate pattern. In addition, FBP21 colocalized with the essential pre-mRNA splicing factor SC35.