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.