TIA1 Prevents Skipping of a Critical Exon Associated with Spinal Muscular Atrophy

Abstract

Prevention of skipping of exon 7 during pre-mRNA splicing of Survival Motor Neuron 2 (SMN2) holds the promise for cure of spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. Here, we report T-cell-restricted intracellular antigen 1 (TIA1) and TIA1-related (TIAR) proteins as intron-associated positive regulators of SMN2 exon 7 splicing. We show that TIA1/TIAR stimulate exon recognition in an entirely novel context in which intronic U-rich motifs are separated from the 5′ splice site by overlapping inhibitory elements. TIA1 and TIAR are modular proteins with three N-terminal RNA recognition motifs (RRMs) and a C-terminal glutamine-rich (Q-rich) domain. Our results reveal that any one RRM in combination with a Q domain is necessary and sufficient for TIA1-associated regulation of SMN2 exon 7 splicing in vivo. We also show that increased expression of TIA1 counteracts the inhibitory effect of polypyrimidine tract binding protein, a ubiquitously expressed factor recently implicated in regulation of SMN exon 7 splicing. Our findings expand the scope of TIA1/TIAR in genome-wide regulation of alternative splicing under normal and pathological conditions.

ACKNOWLEDGMENTS

We express our gratitude to Paul Anderson for providing the mouse TIA1^−/− cell line and Douglas Black for providing the myc-tagged PTB expression vector. We acknowledge technical support provided by Sarah J. Rahn and Katrin Hollinger.

This work was supported by a grant from U.S. National Institutes of Health (R01NS055925) to R.N.S. R.N.S. acknowledges support of Salsbury Endowment at Iowa State University, Ames, IA. N.N.S. was supported by grants from the Center for Integrated Animal Genomics and Iowa Center for Advance Neurotoxicology.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00945-10.