Shape of promoter antisense RNAs regulates ligand-induced transcription activation [Shape-Map]

Demonstration of a massive lncRNA RNA transcriptional program in the mammalian genome has engendered lively discussions about their biological roles, particularly the promoter antisense (PAS) transcripts of coding gene transcription units and abundant species localized to specific subnuclear structures with phase separation properties. Here, we report development of an alternative assay to quantitatively detect RNA distribution in the genome, referred to as ChIRC-seq (Chromatin Isolation by RNA-Cas13a Complex Capture by Cas13a), which has revealed that promoter antisense RNAs (PAS-RNAs) serve as a key gatekeeper of a broad transcriptional pause release program, based on decommissioning the 7SK snRNA-dependent inhibitory P-TEFb complex. Induction of PAS-RNA by liganded estrogen receptor ERα (ESR1) releases the basal recruitment of HP1α and KAP1 on target gene promoters, without the spreading characteristic of extended heterochromatic regions, based on PAS-dependent recruitment of H3K9me3 demethylases. Unexpectedly, ERα-bound MegaTrans enhancer activation with features of phase separation events proved to require recruitment of phosphorylated KAP1 to be activated, with its transfer to the cognate promoters licensing estrogen-induced pause release and target gene activation. The ChIRC13a-seq method has proved effective for identification of the cognate promoter for activated enhancers and has revealed that the lncRNAs NEAT1/MALAT1 in phase-separated subnuclear structures interact with robust estrogen-activated MegaTrans TFF1e1 enhancer and other active enhancers, linking acute activation of a subset of enhancers to interactions with specific phase-separated subnuclear architectural structures. The changes in the gene expression profiles were investigated by ChIP-seq, PRO-seq, and ChIRC-seq. The secondary structure of pasRNA has been mapped by SHAPE-MaP.