Nucleic Acids Research Advance Access published online on October 23, 2009
Nucleic Acids Research, doi:10.1093/nar/gkp766
RNA |
The neurofibromatosis type I pre-mRNA is a novel target of CELF protein-mediated splicing regulation
1Department of Genetics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, 2Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, 3Center for RNA Molecular Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, 4Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195 and 5Case Comprehensive Cancer Center, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
*To whom correspondence should be addressed. Tel: +1 216 368 6419; Fax: +1 216 368 0491; Email: hxl47{at}case.edu
Received April 17, 2009. Revised September 1, 2009. Accepted September 1, 2009.
The CUG-BP and ETR-3 like factors (CELF) are a family of six highly conserved RNA-binding proteins that preferentially bind to UG-rich sequences. One of the key functions of these proteins is to mediate alternative splicing in a number of tissues, including brain, heart and muscle. To fully understand the function of CELF proteins, it is important to identify downstream targets of CELF proteins. In this communication, we report that neurofibromatosis type I (NF1) exon 23a is a novel target of CELF protein-mediated splicing regulation in neuron-like cells. NF1 regulates Ras signaling, and the isoform that excludes exon 23a shows 10 times greater ability to down-regulate Ras signaling than the isoform that includes exon 23a. Five of the six CELF proteins strongly suppress the inclusion of NF1 exon 23a. Over-expression or siRNA knockdown of these proteins in cell transfection experiments altered the levels of NF1 exon 23a inclusion. In vitro binding and splicing analyses demonstrate that CELF proteins block splicing through interfering with binding of U2AF65. These studies, combined with our previous investigations demonstrating a role for Hu proteins and TIA-1/TIAR in controlling NF1 exon 23a inclusion, highlight the complex nature of regulation of this important alternative splicing event.