Hsa-miR-637 inhibits human hepatocyte proliferation by targeting Med1-interacting proteins

Background: Recent studies have shown that mediator complex subunit 1 (Med1) can significantly affect hepatocyte proliferation and differentiation. Acting as a tumor suppressor, microRNA-637 (hsa-miR-637) can inhibit the growth of hepatocarcinoma cells and further induce cell apoptosis. However, the function of hsa-miR-637 and its target genes during liver regeneration remains to be elucidated. Methods: This study used co-immunoprecipitation (Co-IP) assay, transfection, luciferase reporter assay, functional assay by cell counting kit-8 (CCK-8), Annexin V-FITC/propidium iodide apoptosis assay, and quantitative polymerase chain reaction analysis of chromatin immunoprecipitation (ChIP) for analysis. Results: Hsa-miR-637 has been suggested to suppress the expression of two Med1-interacting nuclear receptors, identified as the peroxisome proliferator-activated receptor alpha (PPARA) and thyroid hormone receptor alpha (THRA) at the transcriptional and translational levels in the human liver HL-7702 cell line. The interaction between Med1 and PPARA/THRA in HL-7702 cells was then confirmed. The transcriptional repression of hsa-miR-637 on PPARA and THRA was also demonstrated. Moreover, hsa-miR-637 has been determined to suppress the proliferation of HL-7702 cells. Furthermore, cell cycle arrest of HL-7702 cells was induced by transfection of hsa-miR-637 at the S phase, but its apoptosis failed. Finally, PPARA was indicated to directly bind to the promoter of some transcription factors, like β-catenin, mouse double minute 2 (MDM2), and p53. Conclusions: This study has confirmed that hsa-miR-637 plays an antiproliferative role during liver regeneration, which may contribute in understanding the regenerative process of the liver.