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Novel RNA-binding activity of NQO1 promotes SERPINA1 mRNA translation

ABSTRACT: NAD(P)H:quinone Oxidoreductase (NQO1) is essential for cell defense against reactive oxidative species, cancer, and metabolic stress. Recently, NQO1 was found in ribonucleoprotein (RNP) complexes, but NQO1-interacting mRNAs and the functional impact of such interactions are not known. Here, we used ribonucleoprotein immunoprecipitation (RIP) and microarray analysis to identify comprehensively the subset of NQO1 target mRNAs in human hepatoma HepG2 cells. One of its main targets, SERPINA1 mRNA, encodes the serine protease inhibitor α-1-antitrypsin, A1AT, which is associated with disorders including obesity-related metabolic inflammation, chronic obstructive pulmonary disease (COPD), liver cirrhosis and hepatocellular carcinoma. Biotin pulldown analysis indicated that NQO1 can bind the 3’ untranslated region (UTR) and the coding region (CR) of SERPINA1 mRNA. NQO1 did not affect SERPINA1 mRNA levels; instead, it enhanced the translation of SERPINA1 mRNA, as NQO1 silencing decreased the size of polysomes forming on SERPINA1 mRNA and lowered the abundance of A1AT. Luciferase reporter analysis further indicated that NQO1 regulates SERPINA1 mRNA translation through the SERPINA1 3’UTR. Accordingly, NQO1-KO mice had reduced hepatic and serum levels of A1AT and increased activity of neutrophil elastase, one of the main targets of A1AT. We propose that this novel mechanism of action of NQO1 as RNA-binding protein may help to explain its pleiotropic biological effects.

ORGANISM(S): Homo sapiens

PROVIDER: GSE81614 | GEO | 2017/05/22

SECONDARY ACCESSION(S): PRJNA322081

REPOSITORIES: GEO

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Project description:Regulation of gene expression at the post-transcriptional level plays an indispensable role during TGFbeta-induced EMT and metastasis. This regulation involves a transcript-selective translational regulatory pathway in which a ribonucleoprotein (mRNP) complex, consisting of heterogeneous nuclear ribonucleoprotein E1 (hnRNP E1) and eukaryotic elongation factor 1A1 (eEF1A1), binds to a 3M-bM-^@M-^Y-UTR regulatory BAT (TGFM-NM-2 activated translation) element and silences translation of Dab2 and ILEI mRNAs, two transcripts which are involved in mediating EMT. TGFbeta activates a kinase cascade terminating in the phosphorylation of hnRNP E1, by isoform-specific stimulation of protein kinase B/Akt2, inducing the release of the mRNP complex from the 3M-bM-^@M-^Y-UTR element, resulting in the reversal of translational silencing and increased expression of Dab2 and ILEI transcripts. We adopted a combinatorial approach involving polysome profiling and RIP-Chip analyses using hnRNP E1 and filtered the array data based on the regulatory mechanism of Dab2 and ILEI. This led to the identification and validation of a cohort of target mRNAs that follow the same pattern of regulation as Dab2 and ILEI. To identify potential target mRNA transcripts that are translationally regulated by hnRNP E1 in a TGF-beta-dependent manner, we adopted a combinatorial approach involving expression profiling analyses and RNA immunoprecipitation analysis (RIP-Chip). We performed a screen using: 1) total mRNA and 2) RNA isolated from monosomal (non-translating) versus polysomal (translating) fractions from TGF-beta-treated (24 h) and non-treated NMuMG cells and from the hnRNP E1 knockdown derivative (E1KD), that undergo constitutive EMT even in the absence of TGF-beta. In addition, we screened for transcripts that selectively interact with hnRNP E1 in NMuMG cells under unstimulated conditions and subsequently lose their temporal association following TGF-beta stimulation. The samples were individually hybridized to Affymetrix GeneChipM-BM-. Mouse Genome 430 2.0 arrays.

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Novel RNA-binding activity of NQO1 promotes SERPINA1 mRNA translation

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