An unexpected contribution of lincRNA splicing to enhancer function.

Transcription is common at active mammalian enhancers sometimes giving rise to stable and unidirectionally transcribed enhancer-associated long intergenic noncoding RNAs (elincRNAs). ElincRNA expression is associated with changes in neighboring gene product abundance and local chromosome topology, suggesting that transcription at these loci contributes to gene expression regulation in cis. Despite the lack of evidence supporting sequence-dependent functions for most elincRNAs, splicing of these transcripts is unexpectedly common. Whether elincRNA splicing is a mere consequence of their cognate enhancer activity or if it directly impacts enhancer-associated cis-regulation remains unanswered. Here we show that elincRNAs are efficiently and rapidly spliced and that their processing rate is strongly associated with their cognate enhancer activity. This association is supported by: their enrichment in enhancer-specific chromatin signatures; elevated binding of co-transcriptional regulators, including CBP and p300; increased local intra-chromosomal DNA contacts; and strengthened cis-regulation on target gene expression. Using nucleotide polymorphisms at human elincRNA splice sites, we found that elincRNA splicing enhances their transcription and directly impacts cis-regulatory function of their cognate enhancers. Importantly, up to 90% of human elincRNAs have nucleotide variants that are associated with both their splicing and the expression levels of their proximal genes. Our results highlight the unexpected contribution of elincRNA splicing to enhancer function.