SLUG: a new target of lymphoid enhancer factor-1 in human osteoblasts

Abstract

BackgroundLymphoid Enhancer Factor-1 (Lef-1) is a member of a transcription factor family that acts as downstream mediator of the Wnt/β-catenin signalling pathway which plays a critical role in osteoblast proliferation and differentiation. In a search for Lef-1 responsive genes in human osteoblasts, we focused on the transcriptional regulation of the SLUG, a zinc finger transcription factor belonging to the Snail family of developmental proteins. Although the role of SLUG in epithelial-mesenchymal transition and cell motility during embryogenesis is well documented, the functions of this factor in most normal adult human tissues are largely unknown. In this study we investigated SLUG expression in normal human osteoblasts and their mesenchymal precursors, and its possible correlation with Lef-1 and Wnt/β-catenin signalling.ResultsThe experiments were performed on normal human primary osteoblasts obtained from bone fragments, cultured in osteogenic conditions in presence of Lef-1 expression vector or GSK-3β inhibitor, SB216763. We demonstrated that the transcription factor SLUG is present in osteoblasts as well as in their mesenchymal precursors obtained from Wharton's Jelly of human umbilical cord and induced to osteoblastic differentiation. We found that SLUG is positively correlated with RUNX2 expression and deposition of mineralized matrix, and is regulated by Lef-1 and β-catenin. Consistently, Chromatin Immunoprecipitation (ChIP) assay, used to detect the direct Lef/Tcf factors that are responsible for the promoter activity of SLUG gene, demonstrated that Lef-1, TCF-1 and TCF4 are recruited to the SLUG gene promoter "in vivo".ConclusionThese studies provide, for the first time, the evidence that SLUG expression is correlated with osteogenic commitment, and is positively regulated by Lef-1 signal in normal human osteoblasts. These findings will help to further understand the regulation of the human SLUG gene and reveal the biological functions of SLUG in the context of bone tissue.

Loss of EBP50 stimulates EGFR activity to induce EMT phenotypic features in biliary cancer cells

“…As a result, EGFR activation triggers the phosphorylation of b-catenin (Lee et al, 2010) (dashed arrow), resulting in the disruption of the AJs with E-cadherin internalization and nuclear translocation of b-catenin. In the nucleus, phosphorylated STAT3 and ERK1/2 as well as nuclear b-catenin induce a transcriptional program involved in EMT (for example, Slug mRNA induction) (Lo et al, 2007;Chen et al, 2009;Lambertini et al, 2010). Ultimately, this program leads to actin cytoskeleton remodeling as well as cell dispersion and migration.…”

SLUG-induced Elevation of D1 Cyclin in Breast Cancer Cells through the Inhibition of Its Ubiquitination

“…One of the causes for breast cancer cell proliferation and metastasis is the overexpression of the metastasis modulator transcriptional repressor protein SLUG (27)(28)(29)(30)(31). This protein binds to the E2-box sequence of its target gene promoters and down-regulates their expression by chromatin remodeling (28,32).…”

“…Phosphorylation of retinoblastoma protein prevents it from repressing the E2F family of transcription factors and leads to the transcription of several genes required for the G 1 to S phase transition, thereby promoting cellular proliferation (25). Cyclin D1 is overexpressed in ϳ50% of breast cancers and is implicated as the cause of their increased rate of proliferation (26).One of the causes for breast cancer cell proliferation and metastasis is the overexpression of the metastasis modulator transcriptional repressor protein SLUG (27)(28)(29)(30)(31). This protein binds to the E2-box sequence of its target gene promoters and down-regulates their expression by chromatin remodeling (28,32).…”

Apoptosis Resistance in Rheumatoid Arthritis Synovial Tissue

“…Similar studies in FLS derived from p53 null mice or in human FLS transfected with a dominant-negative mutant p53 indicated that PUMA-induced apoptosis did not require p53. More recently, Cha et al [111] showed that 'slug' protein, encoded by the SNAI2 gene a highly conserved zinc transcriptional repressor belonging to the snail family of developmental proteins [112] was over-expressed in RA synovial tissue. Further, treatment of RAFLS with hydrogen peroxide and suppression of 'slug' gene expression improved FLS apoptosis which was characterized by increased PUMA-mediated transactivation.…”