Spatial organization of transcript elongation and splicing kinetics
The organization of the genome in three-dimensional space has been shown to play an important role in gene expression. Specifically, facets of genomic interaction such as topologically associated domains (TADs) have been shown to regulate transcription by bringing regulatory elements into close proximity1. mRNA production is an intricate process with multiple control points including regulation of Pol II elongation and the removal of non-coding sequences via pre-mRNA splicing2. The connection between genomic compartments and the kinetics of RNA biogenesis and processing has been largely unexplored. Here, we measure Pol II elongation and splicing kinetics genome-wide using a novel technique that couples nascent RNA-seq with a mathematical model of transcription and co-transcriptional RNA processing. We uncovered multiple layers of spatial organization of these rates: the rate of splicing is coordinated across introns within individual genes, and both elongation and splicing rates are coordinated within TADs, as are alternative splicing outcomes. Overall, our work establishes that the kinetics of transcription and splicing are coordinated by the spatial organization of the genome and suggests that TADs are a major platform for coordination of alternative splicing.