Let-7g inhibits synthesis of estradiol by downregulating activity of aromatase in JEG3 cells.

Abstract

Increased production of estrogen in human placenta during pregnancy closely associates with parturition. Aromatase, encoded by CYP19A1 gene, is an enzyme critical for biosynthesis of estrogen. Despite numerous efforts in the past few decades ascribed to characterizing the mechanisms of transcriptional control of aromatase, the posttranscriptional control of CYP19A1 remains poorly understood. In this study, we sought to investigate the role of microRNA, let-7g, in posttranscriptional regulation of aromatase in human trophoblast choriocarcinoma cell line, JEG3. We show that the expression of let-7g was downregulated in JEG3 cell line, but upregulated in primary term trophoblast; conversely, aromatase was upregulated in JEG3 but downregulated in primary trophoblast. We further show that let-7g antagomirs and mimics increased and decreased aromatase expression, respectively; and let-7g directly targeted 3'-untranslated region of CYP19A1 mRNA by using dual luciferase assay. Using ELISA, we also demonstrate that let-7g antagomirs and mimics robustly increased and decreased production of estradiol, respectively. Our results suggest that aromatase expression is regulated at multiple molecular layers in the placenta. These results further suggest that JEG3 cell line is a valuable tool to study additional mechanisms associated with human birth.