title: Hypoxia upregulates Malat1 expression through a CaMKK/AMPK/HIF-1α axis.
abstract: Increased expression levels of the long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (Malat1) have been associated with enhanced proliferation and metastasis of several cancer cell types. Hypoxia, a hallmark characteristic of solid tumors, has been linked to an increase in the activity of the ATP-generating AMPK protein. Since Malat1 was recently shown to be upregulated during hypoxia, the objective of this study was to determine the contribution of AMPK in the mechanistic pathways regulating Malat1 expression in low oxygen conditions. Compared to those cultured in 21% O2 conditions, HeLa cells incubated in 1.5% O2 expressed more Malat1 transcripts. This observation was mimicked in HEK293T cells using a synthetic reporter construct containing 5.6 kb of the human Malat1 promoter, suggesting that hypoxia directly impacted Malat1 gene transcription. Interestingly, pharmacological stimulation of AMPK increased Malat1 promoter transactivation in 21% O2 conditions, whereas inhibition of either AMPK or its upstream activator CaMKK completely abolished the augmentation of Malat1 under hypoxia. Pharmacological modulation of LKB1, another major regulator of AMPK, had no impact on Malat1 promoter transactivation, suggesting that calcium inputs are important in the control of Malat1 expression by AMPK. Overexpression of hypoxia-inducible factor-1α (HIF-1α) increased Malat1 expression in 21% O2 conditions, whereas pharmacological inhibition of HIF-1α blocked the impact of hypoxia on the Malat1 promoter. Taken together, these findings strongly suggest that Malat1 expression is regulated in hypoxic conditions by a CaMKK/AMPK/HIF-1α axis. More research is needed in physiological settings to test the clinical relevance of this pathway.
authors: IUCPQ Research Center, Quebec Heart and Lung Institute, Québec, Canada.
authors: Sandrine
authors: S
authors: Sallé-Lefort
authors: IUCPQ Research Center, Quebec Heart and Lung Institute, Québec, Canada.
authors: Stéphanie
authors: S
authors: Miard
authors: Faculty of Pharmacy, Laval University, Québec, Canada.
authors: Marc-André
authors: MA
authors: Nolin
authors: IUCPQ Research Center, Quebec Heart and Lung Institute, Québec, Canada.
authors: Louise
authors: L
authors: Boivin
authors: IUCPQ Research Center, Quebec Heart and Lung Institute, Québec, Canada.
authors: Marie-Ève
authors: MÈ
authors: Paré
authors: IUCPQ Research Center, Quebec Heart and Lung Institute, Québec, Canada.
authors: Richard
authors: R
authors: Debigaré
authors: IUCPQ Research Center, Quebec Heart and Lung Institute, Québec, Canada.
authors: Frédéric
authors: F
authors: Picard
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D015153:Blotting, Western; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D062085:RNA, Long Noncoding / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D015533:Transcriptional Activation; D015854:Up-Regulation
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C557041:MALAT1 long non-coding RNA, human; D062085:RNA, Long Noncoding; D011494:Protein Kinases; C517695:CAMKK1 protein, human; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D000091162:AMP-Activated Protein Kinase Kinases; D010100:Oxygen