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

ABSTRACT: The epithelial-mesenchymal transition (EMT) is a multistep dedifferentiation program important in tissue repair. Here, we examined the role of the transcriptional regulator NFkB in EMT of human primary small airway epithelial cells (hSAECs). Surprisingly, transforming growth factor β (TGFβ) activated NFkB/RELA proto-oncogene, NFkB 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 TGFβ-induced EMT transition was analyzed by RNA-Seq in the absence or presence of inducible shRNA-mediated silencing of RELA. In WT cells, TGFβ stimulation significantly affected the expression of 2,441 genes. Gene set enrichment analysis identified Wnt, cadherin, and NFkB signaling as the most prominent TGFβ-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/β-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 TGFβ-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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE84135 | GEO | 2018/09/26

REPOSITORIES: GEO

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Project description:Loss of expression of the cell-cell adhesion molecule E-cadherin is an essential event for epithelial-mesenchymal transition (EMT), a process that allows cell migration in the developing embryo and during tumour invasion. Transcriptional repression has emerged as the main mechanism responsible for E-cadherin downregulation in most carcinomas. Recently, we have identified the class I HLH transcriptional regulator E2-2 (ITF2), in a yeast one hybrid screen designed to identify transcriptional repressors interacting with the E-pal element of the murine E-cadherin promoter. The E2-2 gene codifies two isoforms that differ in their N-terminal regions but their specific functions remain unknown. In the present work we show that both E2-2A and E2-2B induce a complete EMT, in MDCK cells, with loss of E-cadherin expression, gain of mesenchymal markers and acquisition of motile and invasive properties. Although both isoforms repress E-cadherin promoter in MDCK cells, only the E2-2B isoform does it in other epithelial cell lines. Notably, we found that E2-2B is upregulated at the mRNA level in MDCK cells after treatment with TGF-ï¢1, a key regulator of EMT. Upregulation of E2-2A/B factors was confirmed in MDCK cells overexpressing other EMT inducers, Snai1, Snai2 or E47. Interestingly, gene profiling studies indicate that bHLH E2-2 factors induce similar, yet distinct, genetic programs from those induced by bHLH E47 in MDCK cells. These results, together with the expression pattern observed in early mouse embryos, support a new role for E2-2A/B in E-cadherin regulation and EMT, and suggest an interesting interplay between bHLH factors and other E-cadherin repressors. Keywords: Genetic Modification (overexpression of E-cadherin repressors) The Oncochip microarray platform v2.0 contains 13,824 clones printed by duplicate corresponding to 9,300 different genes. Each of the MDCK transfectants (E22A, E22B) were labeled with dUTP-Cy5 and hybridized against the dUTP-Cy3-labeled MDCK-CMV controls. One additional hybridizations using reciprocal fluorochrome labeling were performed (dye-swap) in each clone. Thus, a total of two hybridizations were performed for each condition.

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

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