SMITten by the Speed of Splicing

Splicing occurs co-transcriptionally, but relative rates of splicing and transcription that might reveal mechanisms of their coordinated control have remained mysterious. Now, Carrillo Oesterreich et al. show that the fastest introns are gone nearly as soon as the 3′ splice site is transcribed and that introns have distinct splicing kinetics with respect to polymerase progression along the gene.