Coordination of AUF1 and miR-148a destabilizes DNA methyltransferase 1 mRNA under hypoxia in endometriosis

• Published in: Molecular human reproduction 2015-12, Vol.21 (12), p.894-904
• Main Authors: Hsiao, Kuei-Yang, Wu, Meng-Hsing, Chang, Ning, Yang, Shang-Hsun, Wu, Chun-Wei, Sun, H Sunny, Tsai, Shaw-Jenq
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Western; Cell Line; DNA Methylation - genetics; Endometriosis - genetics; Epigenesis, Genetic - genetics; Female; Heterogeneous Nuclear Ribonucleoprotein D0; Heterogeneous-Nuclear Ribonucleoprotein D - metabolism; Immunohistochemistry; Immunoprecipitation; Mice; MicroRNAs - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics
• ISSN: 1360-9947; 1460-2407
• DOI: 10.1093/molehr/gav054

DNA methylation is regulated by hypoxia in endometriosis. Hypoxia causes global hypomethylation through AU-rich element binding factor 1 (AUF1)/microRNA-148a (miR-148a)-mediated destabilization of DNA methyltransferase 1 (DNMT1) mRNA. Eutopic endometrial and ectopic endometriotic stromal cells have the same genetic background, but differ in several cellular and molecular responses. Both hypoxia and DNA methylation regulate several genes involved in the development of endometriosis. This laboratory study included 15 patients of reproductive age with endometriosis or normal menstrual cycles. Paired endometrial and endometriotic tissues were collected for assaying the levels of DNMT1, 3a and 3b using quantitative RT-PCR, western blot and immunohistochemical (IHC) staining. Primary cultured endometrial stromal cells maintained in normoxia/hypoxia (1% O2) or treated with hypoxia-mimetic compounds were also assayed. The levels of DNA 5-methylcytosine were assayed by using IHC in clinical specimens and murine tissues, and by ELISA in cultured stromal cells. The 3'-untranslated region reporter assay was used to evaluate the effect of hypoxia, microRNAs (miRNAs) and human antigen R (HuR)/AUF1 on DNMT1 mRNA stability. RNA immunoprecipitation was used to assess the interaction of HuR/AUF1 and miR-148a/DNMT1 mRNA under hypoxia. Finally, a transplant-induced mouse model of endometriosis using 20 mice was used to elucidate the alteration of Dnmt1 levels and DNA methylation in the endometriotic tissues. Levels of DNMT1 mRNA and protein and 5-methylcytosine were lower in the ectopic stromal cells (P < 0.05) than in the eutopic cells. Treatment with hypoxia and its mimetic compounds recapitulated the reduced levels of DNMT1 and 5-methylcytosine levels (P < 0.05 versus control). Hypoxia treatment destabilized DNMT1 mRNA through recruitment of miR-148a and AUF1. Mutations introduced to the miR-148a targeting site or AU-rich element (ARE) restored the hypoxia-suppressed DNMT1 3'-untranslated region (3'-UTR) reporter activity (P < 0.05 versus control). Levels of proteins of three hypermethylated genes in endometrial stroma cells, GATA6, HOXA3 and SLC16A5, were elevated after 72 h of hypoxia treatment (P < 0.05 versus control). Finally, a transplant-induced model of endometriosis demonstrated the down-regulation of DNMT1 and a decrease in 5-methylcytosine in the endometriotic tissues (P < 0.05, eutopic versus ectopic). Primary human cell cultures and a murine model were used in