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Description

Polypyrimidine tract-binding protein 1 (UniProt P26599, also known as 57 kDa RNA-binding protein PPTB-1, Heterogeneous nuclear ribonucleoprotein I, Heterogeneous nuclear ribonucleoprotein polypeptide I, hnRNP I, PTB, RNA-binding protein) is encoded by the PTBP1 (also known as HNRNP-I, HNRNPI, HNRPI, PTB, PTB2, PTB3, PTB4, PTB-1, PTB-T) gene (Gene ID 5725) in human. The serine-arginine rich (SR) proteins and the heterogeneous nuclear ribonucleoproteins (hnRNPs) are the most typical families of RBPs involved in splicing regulation. SR proteins generally play a positive role in exon recognition by binding exonic and intronic enhancers near the alternative splice sites. On the other hand, hnRNPs often bind to silencer elements and interfere with the recruitment of spliceosome components or positive regulators. PTB, also known as hnRNP I, belongs to an hnRNP family of RNA-binding proteins and is involved in several aspects of cellular mRNA metabolism including splicing, RNA stability, and internal ribosome entry site (IRES)-mediated translation of viral and cellular mRNAs. PTB functions as a splicing repressor by preventing recruitment of U2AF65 or correct base pairing of U2 snRNP, or by affecting the interaction of U1 snRNP with other components of the spliceosome.