\u03b2-Catenin/LEF-1 transcription complex is responsible for the transcriptional activation of LINC01278

Abstract

BackgroundOur previous study shows that LINC01278 inhibits the malignant proliferation and invasion of papillary thyroid carcinoma (PTC) cells by regulating the miR-376c-3p/DNM3 axis. However, the regulation mechanism of LINC01278 expression in PTC cells is still unclear.MethodsThe luciferase reporter and ChIP assays were used to confirm the binding of LEF-1 to the putative promoter site of LINC01278 gene. The RNA immunoprecipitation and RNA pulldown were used to determine the enrichment of LINC01278 in β-catenin protein. The proteasome inhibitors (MG132) was used for detecting the β-catenin ubiquitination-proteasome degradation. Wnt/β-catenin specific agonists (LiCI), inhibitors (WiKI4) and TOP/FOP-flash reporter assay were used for detecting the activation of Wnt/β-catenin signal. Western blot was used to detected the expression of target proteins.ResultsThe online PROMO algorithm determines a putative LEF-1 binding site on LINC01278 promoter, the LEF-1 binds to the putative promoter site of LINC01278 gene, and β-catenin enhances the binding of LEF-1 to the LINC01278 gene promoter. Furthermore, LINC01278 negatively regulated the protein accumulation of β-catenin in the cytoplasm, into nucleus, and ultimately inhibited the transcription of downstream target genes activated by Wnt/β-catenin signal. The results of RNA immunoprecipitation and RNA pulldown proved the direct binding of LINC01278 to β-catenin protein. In addition, the combination of LINC01278 and β-catenin promotes the β-catenin ubiquitination-proteasome degradation.ConclusionIn summary, we found the transcriptional activation of LINC01278 by the β-catenin/LEF-1 transcription factor, and the negative feedback regulation of LINC01278 onβ-catenin signal.