Introns in UTRs: Why we should stop ignoring them

Abstract

Although introns in 5′- and 3′-untranslated regions (UTRs) are found in many protein coding genes, rarely are they considered distinctive entities with specific functions. Indeed, mammalian transcripts with 3′-UTR introns are often assumed nonfunctional because they are subject to elimination by nonsense-mediated decay (NMD). Nonetheless, recent findings indicate that 5′- and 3′-UTR intron status is of significant functional consequence for the regulation of mammalian genes. Therefore these features should be ignored no longer. Whereas introns in coding regions are well-appreciated for their role in producing alternative protein isoforms, introns in untranslated regions (UTRs) have been largely ignored. Recent evidence shows that UTR introns are important for regulating gene expression; introns in 5′-UTRs control mRNA nuclear export, and introns in 3′-UTRs regulate mRNA stability. © 2012 WILEY Periodicals, Inc.