Project description:RNA binding proteins play an important role in regulating alternative pre-mRNA splicing and in turn cellular gene expression. Polypyrimidine tract binding proteins, PTBP1 and PTBP2, are paralogous RNA binding proteins that play a critical role in the process of neuronal differentiation and maturation; changes in the concentration of PTBP proteins during neuronal development direct splicing changes in many transcripts that code for proteins critical for neuronal differentiation. How the two related proteins regulate different sets of neuronal exons is unclear. The distinct splicing activities of PTBP1 and PTBP2 can be recapitulated in an in vitro splicing system with the differentially regulated N1 exon of the c-src pre-mRNA. Here, we conducted experiments under these in vitro splicing conditions to identify PTBP1 and PTBP2 interacting partner proteins.
Project description:During B cell development, recombination of immunoglobulin loci is tightly coordinated with the cell cycle to avoid unwanted rearrangements of other genomic locations. Several factors have been identified that suppress proliferation in late-pre-B cells to allow light chain recombination. By comparison, our knowledge of factors limiting proliferation during heavy chain recombination at the pro-B cell stage is very limited. Here we identify an essential role for the RNA-binding protein Polypyrimidine Tract Binding Protein 1 (PTBP1) in B cell development. Absence of PTBP1 and the paralog PTBP2 results in a complete block in development at the pro-B cell stage. PTBP1 promotes the fidelity of the transcriptome in pro-B cells. In particular, PTBP1 controls a cell cycle mRNA regulon, suppresses entry into S-phase and promotes progression into mitosis. Our results highlight the importance of S-phase entry suppression and post-transcriptional gene expression control by PTBP1 in pro-B cells for proper B cell development.
Project description:We show that the RNA-binding protein Polypyrimidine Tract Binding Protein 1 (PTBP1) is dispensable for the development of naïve mouse CD8 T cells, but is necessary for the optimal expansion and production of effector molecules by antigen-specific CD8 T cells in vivo. PTBP1 has an essential role in regulating the early events following activation of the naïve CD8 T cell leading to IL-2 and TNF production. It is also required to protect activated CD8 T cells from apoptosis. PTBP1 controls alternative splicing of over 400 genes in naïve CD8 T cells in addition to regulating the abundance of ~200 mRNAs. PTBP1 is required for the nuclear accumulation of c-Fos, NFATc2 and NFATc3, but not NFATc1. This selective effect on NFAT proteins correlates with PTBP1-promoted expression of the shorter Ab1 isoform and exon 13 skipped Ab2 isoform of the catalytic A-sububit of calcineurin phosphatse. These findings reveal a crucial role for PTBP1 in regulating CD8 T cell activation.
Project description:Changing splicing factors leads to abnormal alternative splicing (AS), which results in tumor progression.Splicing factor polypyrimidine tract binding proteins (PTBP1) facilitate cancer progression by modulating oncogenic variants. However, its role and mechanism in hepatocellular carcinoma (HCC) remains unclear. Our findings confirm that PTBP1 is highly expressed in HCC cells lines and tissues. Moreover, its expression correlated negatively with overallanddisease-freesurvivalrates, but inversely with tumor grade and stage. PTBP1 knockdown decreases HCC cell proliferation, migration, and invasion in vitro and inhibits hepatoma xenograft growth and infiltration in vivo. We identified PTBP1-mediated AS events and PTBP1 functionally promoted cell proliferation, invasion, and migration by altering the AS of the protein tau (MAPT) gene and promoting the oncogene expression. Strikingly, the dysregulation of MAPT splicing was paralleled by the increased expression of PTBP1 in HCC, which predicted the poor prognosis of the patients. According to additional research, AS of the MAPT gene guided by PTBP1 increases tumorigenicity in HCC by activating the MAPK/ERK pathways. In summary, our results suggest that PTBP1 plays an oncogenic role in HCC partially through the regulation of MAPT's AS, which could be a promising treatment target.