Factor inhibiting HIF1–A novel target of SUMOylation in the human placenta
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Julien Sallais1,2, Sruthi Alahari1,3, Andrea Tagliaferro1, Jayonta Bhattacharjee1, Martin Post2,3,5 and Isabella Caniggia1,2,3,4
1Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
2Department of Obstetrics and Gynaecology, University of Toronto, Ontario, Canada
3Department of Physiology, University of Toronto, Ontario, Canada
4Institute of Medical Sciences University of Toronto, Toronto, Ontario, Canada
5Program in Physiology and Experimental Medicine, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Ontario, Canada
Isabella Caniggia, email: email@example.com
Keywords: factor Inhibiting HIF; hypoxia-inducible factor; SUMOylation; placenta; preeclampsia
Received: July 22, 2017 Accepted: November 15, 2017 Published: December 07, 2017
Adaptations to changes in oxygen are critical to ensure proper placental development, and impairments in oxygen sensing mechanisms characterize placental pathologies such as preeclampsia. In this study, we examined the involvement of SUMOylation, a reversible posttranslational modification, in the regulation of the asparaginyl hydroxylase Factor Inhibiting Hypoxia Inducible Factor 1 (FIH1) in the human placenta in development and in disease status. FIH1 protein abundance and spatial distribution in the developing placenta directly correlated with oxygen tension in vivo. Immunofluorescence analysis showed that early on FIH1 primarily localized to nuclei of cytotrophoblast cells, while after 10 weeks of gestation it was present in nuclei and cytoplasm of both cytotrophoblast and syncytiotrophoblast cells. Exposure of choriocarcinoma JEG-3 cells to hypoxia induced FIH1 SUMOylation by promoting its association to SUMO2/3. Transfection of JEG-3 cells with FIH1 constructs containing SUMO-mutated sites revealed that SUMOylation of FIH1 by SUMO2/3 targeted it for proteasomal degradation, particularly in hypoxia. SUMOylation of FIH1 directly impacted on HIF1A activity as determined by HIF-responsive luciferase assay. Co-immunoprecipitation analyses revealed enhanced FIH1-SUMO2/3 associations early in development, when FIH1 levels are low, while deSUMOylation of FIH1 by SENP3 increased later in gestation, when FIH1 levels are rising. In preeclampsia, decreased FIH1 protein expression associated with impaired deSUMOylation by SENP3 and increased association with the ubiquitin ligase RNF4. We propose a novel mode of regulation of FIH1 stability by dynamic SUMOylation and deSUMOylation in the human placenta in response to changing oxygen tension, thereby mediating HIF1A transcriptional activity in physiological and pathological conditions.
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