PTBP1
Description
The PTBP1 (polypyrimidine tract binding protein 1) is a protein-coding gene located on chromosome 19.
Polypyrimidine tract-binding protein 1 is a protein that in humans is encoded by the PTBP1 gene. This gene belongs to the subfamily of ubiquitously expressed heterogeneous nuclear ribonucleoproteins (hnRNPs). The hnRNPs are RNA-binding proteins and they complex with heterogeneous nuclear RNA (hnRNA). These proteins are associated with pre-mRNAs in the nucleus and appear to influence pre-mRNA processing and other aspects of mRNA metabolism and transport. While all of the hnRNPs are present in the nucleus, some seem to shuttle between the nucleus and the cytoplasm. The hnRNP proteins have distinct nucleic acid binding properties. The protein encoded by this gene has four repeats of quasi-RNA recognition motif (RRM) domains that bind RNAs. This protein binds to the intronic polypyrimidine tracts that requires pre-mRNA splicing and acts via the protein degradation ubiquitin-proteasome pathway. It may also promote the binding of U2 snRNP to pre-mRNAs. This protein is localized in the nucleoplasm and it is also detected in the perinucleolar structure.
PTBP1 plays a crucial role in pre-mRNA splicing, regulating alternative splicing events. It promotes exon skipping of its own pre-mRNA during muscle cell differentiation. PTBP1 binds to the polypyrimidine tract of introns, potentially promoting RNA looping when bound to two such tracts within the same pre-mRNA. It may also facilitate the binding of U2 snRNP to pre-mRNA. PTBP1 collaborates with RAVER1 in modulating the switching between mutually exclusive exons during the maturation of the TPM1 pre-mRNA. It represses the splicing of MAPT/Tau exon 10. Furthermore, PTBP1 binds to the polypyrimidine-rich controlling element (PCE) of CFTR, promoting exon skipping of CFTR exon 9, thereby counteracting TIA1's role in exon inclusion of CFTR exon 9. PTBP1 influences the splicing of pyruvate kinase PKM by binding repressively to a polypyrimidine tract flanking PKM exon 9, inhibiting exon 9 inclusion and leading to exon 10 inclusion and the production of the PKM M2 isoform. In the context of picornavirus infection, PTBP1 binds to the viral internal ribosome entry site (IRES) and stimulates IRES-mediated translation.
PTBP1 is also known as HNRNP-I, HNRNPI, HNRPI, PTB, PTB-1, PTB-T, PTB2, PTB3, PTB4, pPTB.
