Mechanistic insight into SP1-mediated transcriptional activation of the long non-coding RNA MIR100HG.

MIR100HG is a long non-coding RNA (lncRNA) implicated in tumorigenesis and progression across multiple cancer types. In this study, SP1 expression was modulated by overexpression and stable silencing in Hep3B cells under normoxic and hypoxic conditions and verified at both the mRNA and protein levels. Functional assays demonstrated that SP1 overexpression significantly suppressed cell proliferation, migration, colony formation, and epithelial-mesenchymal transition (EMT), whereas SP1 silencing promoted these malignant phenotypes. Rescue experiments further demonstrated that MIR100HG overexpression in SP1-silenced cells further increased cell proliferation, colony formation, and migration under both normoxic and hypoxic conditions, supporting a functional interaction between SP1 and MIR100HG. To investigate the transcriptional regulation of MIR100HG, luciferase reporter assays showed that SP1 significantly increased the activity of all MIR100HG promoter fragments. Bioinformatic analysis identified multiple putative SP1-binding sites within the MIR100HG promoter, which were subsequently validated by chromatin immunoprecipitation (ChIP). ChIP assays confirmed significant SP1 enrichment at two promoter regions (+51/-155 and - 260/-465), demonstrating direct binding of SP1 to the MIR100HG promoter. Collectively, these findings provide the first direct evidence that SP1 transcriptionally activates MIR100HG while simultaneously suppressing malignant cellular phenotypes, revealing a novel SP1-MIR100HG regulatory axis that may contribute to hepatocellular carcinoma progression in an oxygen-dependent manner.