Tracking intron removal in real time

Abstract

Are all introns spliced cotranscriptionally? In a recent issue of Cell, Vargas et al. (2011) reported single-molecule analyses of pre-mRNA splicing, confirming transcription-coupled splicing of constitutive introns but finding off-site and delayed splicing of alternative introns. The results raise the question of whether kinetics distinguishes constitutive from regulated splicing.