title: NAD(P)H:quinone oxidoreductase 1 (NQO1) competes with 20S proteasome for binding with C/EBPα leading to its stabilization and protection against radiation-induced myeloproliferative disease.
abstract: NAD(P)H:quinone oxidoreductase 1 (NQO1) is a flavoprotein that protects cells against radiation and chemical-induced oxidative stress. Disruption of NQO1 gene in mice leads to increased susceptibility to myeloproliferative disease. In this report, we demonstrate that NQO1 controls the stability of myeloid differentiation factor C/EBPα against 20S proteasomal degradation during radiation exposure stress. Co-immunoprecipitation studies showed that NQO1, C/EBPα, and 20S all interacted with each other. C/EBPα interaction with 20S led to the degradation of C/EBPα. NQO1 in presence of its cofactor NADH protected C/EBPα against 20S degradation. Deletion and site-directed mutagenesis demonstrated that NQO1 and 20S competed for the same binding region (268)SGAGAGKAKKSV(279) in C/EBPα. Mutagenesis studies also revealed that NQO1Y127/Y129 required for NADH binding is essential for NQO1 stabilization of C/EBPα. Exposure of mice and HL-60 cells to 3 Grays of γ-radiation led to increased NQO1 that stabilized C/EBPα against 20S proteasomal degradation. This mechanism of NQO1 regulation of C/EBPα may provide protection to bone marrow against adverse effects of radiation exposure. The studies have significance for human individuals carrying hetero- or homozygous NQO1P187S mutation and are deficient or lack NQO1 protein.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
authors.forename: Junkang
authors.initials: J
authors.lastname: Xu
authors.forename: Anil K
authors.initials: AK
authors.lastname: Jaiswal
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001853:Bone Marrow / Q000378:metabolism / Q000473:pathology; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005720:Gamma Rays / Q000009:adverse effects*; D018922:HL-60 Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D009196:Myeloproliferative Disorders / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism*; D009249:NADP / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics / Q000528:radiation effects; D055550:Protein Stability / Q000528:radiation effects; D059748:Proteolysis / Q000528:radiation effects*; D011833:Radiation Injuries, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; C515848:CEBPA protein, human; C530718:CEBPA protein, mouse; D009249:NADP; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; C491732:Nqo1 protein, mouse; D046988:Proteasome Endopeptidase Complex