title: NUDT2 Disruption Elevates Diadenosine Tetraphosphate (Ap4A) and Down-Regulates Immune Response and Cancer Promotion Genes.
abstract: Regulation of gene expression is one of several roles proposed for the stress-induced nucleotide diadenosine tetraphosphate (Ap4A). We have examined this directly by a comparative RNA-Seq analysis of KBM-7 chronic myelogenous leukemia cells and KBM-7 cells in which the NUDT2 Ap4A hydrolase gene had been disrupted (NuKO cells), causing a 175-fold increase in intracellular Ap4A. 6,288 differentially expressed genes were identified with P < 0.05. Of these, 980 were up-regulated and 705 down-regulated in NuKO cells with a fold-change ≥ 2. Ingenuity® Pathway Analysis (IPA®) was used to assign these genes to known canonical pathways and functional networks. Pathways associated with interferon responses, pattern recognition receptors and inflammation scored highly in the down-regulated set of genes while functions associated with MHC class II antigens were prominent among the up-regulated genes, which otherwise showed little organization into major functional gene sets. Tryptophan catabolism was also strongly down-regulated as were numerous genes known to be involved in tumor promotion in other systems, with roles in the epithelial-mesenchymal transition, proliferation, invasion and metastasis. Conversely, some pro-apoptotic genes were up-regulated. Major upstream factors predicted by IPA® for gene down-regulation included NFκB, STAT1/2, IRF3/4 and SP1 but no major factors controlling gene up-regulation were identified. Potential mechanisms for gene regulation mediated by Ap4A and/or NUDT2 disruption include binding of Ap4A to the HINT1 co-repressor, autocrine activation of purinoceptors by Ap4A, chromatin remodeling, effects of NUDT2 loss on transcript stability, and inhibition of ATP-dependent regulatory factors such as protein kinases by Ap4A. Existing evidence favors the last of these as the most probable mechanism. Regardless, our results suggest that the NUDT2 protein could be a novel cancer chemotherapeutic target, with its inhibition potentially exerting strong anti-tumor effects via multiple pathways involving metastasis, invasion, immunosuppression and apoptosis.
authors.affiliation: Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool, Merseyside, United Kingdom.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Marriott
authors.affiliation: Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, Merseyside, United Kingdom.
authors.forename: Olga
authors.initials: O
authors.lastname: Vasieva
authors.affiliation: Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, Merseyside, United Kingdom.
authors.forename: Yongxiang
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Division of Biomedical and Life Sciences, University of Lancaster, Lancaster, Lancashire, United Kingdom.
authors.forename: Nikki A
authors.initials: NA
authors.lastname: Copeland
authors.affiliation: Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool, Merseyside, United Kingdom.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: McLennan
authors.affiliation: Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool, Merseyside, United Kingdom.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Jones
mesh_terms: D045744:Cell Line, Tumor; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D015536:Down-Regulation; D020869:Gene Expression Profiling; D055786:Gene Knockout Techniques; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000172:deficiency* / Q000235:genetics; D000096964:Nudix Hydrolases
chemical_list: D015226:Dinucleoside Phosphates; D010744:Phosphoric Monoester Hydrolases; C020733:diadenosine tetraphosphate; C557514:NUDT2 protein, human; D000096964:Nudix Hydrolases