Gene-to-gene coordinated regulation of transcription and alternative splicing by 3D chromatin remodeling upon NF-?B activation
The p65/RelA factor of NF-?B plays a pivotal role in coordinating gene expression in response to diverse stimuli, including viral infections. At the chromatin level, p65/RelA governs gene transcription and alternative splicing (AS) through promoter enrichment and genomic exon occupancy, respectively. However, the mechanisms underlying the coordination of these processes remain elusive. In this study, we employed the HTLV-1 Tax viral oncoprotein, a potent activator of NF-?B, to investigate the integrative relationship between 3D chromatin architecture and NF-?B-regulated AS. Our analysis revealed that Tax induces a significant reorganization of the 3D genome, resulting in the formation of multigene complexes that comprise genes co-regulated in transcription and in AS. Notably, we found that the Tax-induced gene-gene contact between the two master genes NFKBIA and RELA is associated with their differential regulation in gene expression and alternative splicing, respectively. Through dCas9-mediated approaches, we demonstrated that NFKBIA-RELA interaction is required for alternative splicing regulation and is caused by an intragenic enrichment of p65/RelA on RELA. Via this mechanism, Tax promotes the expression of the splice isoform RELA?E6 that exhibits specific gene transactivation capacity at the protein level. Our findings shed light on new regulatory mechanisms upon HTLV-1 Tax and underscore the crucial role of p65/RelA in coordinated regulation of NF-?B-responsive genes at both transcriptional and alternative splicing levels in the context of the 3D genome. Overall design: 4C-seq experiments on 293 HEK cells expressing or not the HTLV-1 TAX protein