Rbms3, an RNA-binding protein, mediates the expression of Ptf1a by binding to its 3′UTR during mouse pancreas development

The development of the pancreas is a complicated process that is regulated on several levels. Pancreas transcription factor 1, alpha subunit (Ptf1a), also known as p48, is a pancreas-specific basic helix-loop-helix transcription factor that is critical for both exocrine pancreas development and maintenance of acinar cell differentiation. Based on a differential screening assay, we identified Rbms3, a gene encoding a glycine-rich RNA-binding protein, to be specifically expressed in the neural tube and the pancreatic rudiment of e10.5 embryos. The presence of Rbms3 in the early developing pancreas suggests that specific post-transcriptional regulation mechanisms play an important role in controlling pancreas development. In this study, we show that Rbms3 binds to the 3′UTR of Ptf1a mRNA, but not the 3′UTR of Pdx1, which is another pancreatic transcription factor. The ectopic expression of Rbms3 stimulates the translation of a reporter gene carrying the Ptf1a 3′UTR. In addition, when Rbms3 expression is suppressed in the AR42J-B13 pancreatic exocrine cell line, the expression of Ptf1a is also down-regulated. These results suggest that binding of Rbms3 to the 3′UTR of Ptf1a regulates the production of the Ptf1a protein and, thereby, indirectly regulates the expression of the Ptf1a downstream target genes.