Nelfb Regulates Inflammatory Gene Programs in Dermal Fibroblasts Through Transcriptional Regulation of the NF-κB/IκB Axis

Promoter-proximal pausing of RNA Polymerase II (RNA Pol II) is enforced by the Negative Elongation Factor (NELF) complex, a widespread checkpoint controlling stimulus-responsive gene expression. Nelfb has established context-dependent roles in immunity, but its function in dermal fibroblasts remains unexplored. Here, we show that conditional deletion of Nelfb in dermal fibroblasts de-represses inflammatory gene expression under basal conditions. CUT&RUN chromatin profiling revealed that Nelfb does not occupy the promoters of these inflammatory genes, indicating an indirect mechanism. Instead, Nelfb occupies the transcription start site of Nfkbia, encoding the NF-κB inhibitor IκBα, and promotes productive RNA Pol II elongation at this locus. Loss of Nelfb reduced Nfkbia expression, drove constitutive nuclear NF-κB translocation, and de-repressed NF-κB target genes. Knockdown of RelA by siRNA rescued the majority of this phenotype, confirming NF-κB as the downstream effector. These findings identify Nelfb as an upstream regulator of the NF-κB/IκB axis maintaining dermal immune homeostasis.