InterPro domain: IPR021790

This entry represents the RNA recognition motif 2 (RRM2) of polypyrimidine tract-binding protein 1 (PTBP1) and related proteins. Proteins containing this domain include PTBP1/2/3 (or PTB1/2/3) and heterogeneous nuclear ribonucleoprotein L-like (HNRNPLL) proteins.

PTB can shuttle between nucleus and cytoplasm. It is a splicing repressor factor implicated in the control of alternative exon selection during mRNA processing of many different transcribed genes, including its own pre-mRNA. It is also involved in internal ribosome entry site (IRES)-mediated translation initiation. It may also be involved in the 3'-end processing, localization, and stability of several mRNAs. Two PTB homologues, PTBP2 and PTBP3, are generally expressed in mammalian tissues. PTBP2 is expressed at high levels in adult brain, muscle and testis, while PTBP3 is expressed preferentially in haematopoietic cells [ 1 ]. PTB and PTBP2 bind to the same RNA sequences and have similar effects on alternative splicing events. However, differential expression of PTB and PTBP2 can lead to the generation of alternatively spliced mRNAs [ 2 ]. During neuronal differentiation, MicroRNA miR-124 downregulates PTBP1 expression, which in turn leads to upregulation of PTBP2. Later in development, the expression of PTBP2 decreases and this leads to a second wave of alternative splicing changes characteristic of adult brain and essential for brain development [ 3 ]. PTBP3 may be involved in nonsense-mediated mRNA decay [ 4 ].

1. New insights into functional roles of the polypyrimidine tract-binding protein. Int J Mol Sci 14, 22906-32
2. Solution and crystal structures of a C-terminal fragment of the neuronal isoform of the polypyrimidine tract binding protein (nPTB). PeerJ 2, e305
3. Generation of functionally distinct isoforms of PTBP3 by alternative splicing and translation initiation. Nucleic Acids Res. 43, 5586-600
4. A new function of ROD1 in nonsense-mediated mRNA decay. FEBS Lett. 586, 1101-10