The NFκB subunit RELA is a master transcriptional regulator of the committed epithelial-mesenchymal transition in airway epithelial cells

The epithelial-mesenchymal transition (EMT) is a multistep dedifferentiation program important in tissue repair. Here, we examined the role of the transcriptional regulator NF-B in EMT of primary human small airway epithelial cells (hSAECs). Surprisingly, transforming growth factor (TGF) activated NF-B/RELA proto-oncogene, NF-B subunit (RELA) translocation within 1 day of stimulation, yet induction of its downstream gene regulatory network occurred only after 3 days. A time course of TGF-induced EMT transition was analyzed by RNA-Seq in the absence or presence of inducible shRNA-mediated silencing of RELA. In WT cells, TGF stimulation significantly affected the expression of 2,441 genes. Gene set enrichment analysis identified WNT, cadherin, and NF-B signaling as the most prominent TGF-inducible pathways. By comparison, RELA controlled expression of 3,138 overlapping genes mapping to WNT, cadherin, and chemokine signaling pathways. Conducting upstream regulator analysis, we found that RELA controls six clusters of upstream transcription factors, many of which overlapped with a transcription factor topology map of EMT developed earlier. RELA triggered expression of three key EMT pathways: 1) the WNT/-catenin morphogen pathway, 2) the JUN transcription factor, and 3) the Snail family transcriptional repressor 1 (SNAI1). RELA binding to target genes was confirmed by ChIP. Experiments independently validating WNT dependence on RELA were performed by silencing RELA via genome editing and indicated that TGF-induced WNT5B expression and downstream activation of the WNT target AXIN2 are RELA-dependent. We conclude that RELA is a master transcriptional regulator of EMT upstream of WNT morphogen, JUN, SNAI1-ZEB1, and interleukin-6 autocrine loops.