Promoter architecture and enhancer-driven regulation of Cdh1 during MET

E-cadherin (Cdh1) reactivation is a hallmark of the mesenchymal-to-epithelial transition (MET); however, the direct regulatory mechanisms controlling Cdh1 promoter activity remain incompletely understood. Here, we systematically analyzed the responsiveness of the Cdh1 promoter to MET-associated transcription factors using luciferase reporter assays and chromatin immunoprecipitation. An extended Cdh1 promoter fragment exhibited strong basal activity but limited modulation during EMT or MET. Promoter truncation modestly increased basal activity but was insufficient for robust activation. In contrast, integrating a Grhl3-responsive enhancer dramatically enhanced promoter responsiveness, enabling activation by Grhl3 and cooperative enhancement with Hnf4α. Chromatin immunoprecipitation confirmed Grhl3 enrichment at the Cdh1 promoter region during MET, consistent with the enhanced promoter responsiveness observed upon enhancer integration. These findings demonstrate that the dynamic regulation of Cdh1 expression during epithelial plasticity requires coordinated enhancer-promoter interactions and transcription factor recruitment to overcome intrinsic promoter constraints.