title: Evidence for microRNA-mediated regulation of steroidogenesis by hypoxia.
abstract: Environmental hypoxia can occur in both natural and occupational environments. Over the recent years, the ability of hypoxia to cause endocrine disruption via perturbations in steroid synthesis (steroidogenesis) has become increasingly clear. To further understand the molecular mechanism underlying hypoxia-induced endocrine disruption, the steroid-producing human cell line H295R was used to identify microRNAs (miRNAs) affecting steroidogenic gene expression under hypoxia. Hypoxic treatment of H295R cells resulted in the downregulation of seven steroidogenic genes and one of these, CYP19A1 (aromatase), was shown to be regulated by the transcription factor hypoxia-inducible factor-1 (HIF-1). Using bioinformatic and luciferase reporter analyses, miR-98 was identified to be a CYP19A1-targeting miRNA from a subset of HIF-1-inducible miRNAs. Gain- and loss-of-function analysis suggested that under hypoxia, the increased expression of miR-98 led to the downregulation of CYP19A1 mRNA and protein expression and that it may have contributed to a reduction in estradiol (E2) production. Intriguingly, luciferase reporter assays using deletion constructs of a proximal 5′-flanking region of miR-98 did not reveal a hypoxia-responsive element (HRE)-containing promoter. Overall, this study provided evidence for the role of miRNAs in regulating steroidogenesis and novel insights into the molecular mechanisms of hypoxia-induced endocrine disruption.
authors.forename: Richard Man Kit
authors.initials: RM
authors.lastname: Yu
authors.forename: Gayathri
authors.initials: G
authors.lastname: Chaturvedi
authors.forename: Steve Kwan Hok
authors.initials: SK
authors.lastname: Tong
authors.forename: Suraia
authors.initials: S
authors.lastname: Nusrin
authors.forename: John Paul
authors.initials: JP
authors.lastname: Giesy
authors.forename: Rudolf Shiu Sun
authors.initials: RS
authors.lastname: Wu
authors.forename: Richard Yuen Chong
authors.initials: RY
authors.lastname: Kong
mesh_terms: D020413:3' Untranslated Regions; D001141:Aromatase / Q000378:metabolism*; D015687:Cell Hypoxia; D002460:Cell Line; D015536:Down-Regulation; D004958:Estradiol / Q000096:biosynthesis; D004967:Estrogens / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D013256:Steroids / Q000096:biosynthesis*
chemical_list: D020413:3' Untranslated Regions; D004967:Estrogens; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C546084:MIRN98 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D013256:Steroids; D004958:Estradiol; D001141:Aromatase; C561410:CYP19A1 protein, human