title: The RNA-editing enzyme APOBEC1 requires heterogeneous nuclear ribonucleoprotein Q isoform 6 for efficient interaction with interleukin-8 mRNA.
abstract: Apolipoprotein B mRNA-editing enzyme, catalytic polypeptide 1 (APOBEC1) is an intestine-specific RNA-binding protein. However, inflammation or exposure to DNA-damaging agents can induce ectopic APOBEC1 expression, which can result in hepatocellular hyperplasia in animal models. To identify its RNA targets, FLAG-tagged APOBEC1 was immunoprecipitated from transfected HuH7.5 hepatocellular carcinoma cells and analyzed using DNA microarrays. The interleukin-8 (IL8) mRNA was the most abundant co-precipitated RNA. Exogenous APOBEC1 expression increased IL8 production by extending the half-life of the IL8 mRNA. A cluster of AU-rich elements in the 3'-UTR of IL8 was essential to the APOBEC1-mediated increase in IL8 production. Notably, IL8 mRNA did not co-immunoprecipitate with APOBEC1 from lysates of other cell types at appreciable levels; therefore, other factors may enhance the association between APOBEC1 and IL8 mRNA in a cell type-specific manner. A yeast two-hybrid analysis and siRNA screen were used to identify proteins that enhance the interaction between APOBEC1 and IL8 mRNA. Heterogeneous nuclear ribonucleoprotein Q (hnRNPQ) was essential to the APOBEC1/IL8 mRNA association in HuH7.5 cells. Of the seven hnRNPQ isoforms, only hnRNPQ6 enabled APOBEC1 to bind to IL8 mRNA when overexpressed in HEK293 cells, which expressed the lowest level of endogenous hnRNPQ6 among the cell types examined. The results of a reporter assay using a luciferase gene fused to the IL8 3'-UTR were consistent with the hypothesis that hnRNPQ6 is required for APOBEC1-enhanced IL8 production. Collectively, these data indicate that hnRNPQ6 promotes the interaction of APOBEC1 with IL8 mRNA and the subsequent increase in IL8 production.
authors.affiliation: Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, 1-7-1, Kohnodai, Ichikawa, Chiba 272-8516, Japan,. Electronic address: lbshimizuyk@hospk.ncgm.go.jp.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, 1-7-1, Kohnodai, Ichikawa, Chiba 272-8516, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Nishitsuji
authors.affiliation: Department of Gastroenterology and Hepatology, Graduate School of Medicine, Kyoto University, 54, Kawaramachi, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan, and.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Marusawa
authors.affiliation: Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, 1-7-1, Kohnodai, Ichikawa, Chiba 272-8516, Japan.
authors.forename: Saneyuki
authors.initials: S
authors.lastname: Ujino
authors.affiliation: Department of Life and Environmental Sciences, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takaku
authors.affiliation: Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, 1-7-1, Kohnodai, Ichikawa, Chiba 272-8516, Japan.
authors.forename: Kunitada
authors.initials: K
authors.lastname: Shimotohno
mesh_terms: D020413:3' Untranslated Regions; D000071479:APOBEC-1 Deaminase; D045744:Cell Line, Tumor; D003564:Cytidine Deaminase / Q000378:metabolism*; D057809:HEK293 Cells; D006207:Half-Life; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques
chemical_list: D020413:3' Untranslated Regions; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D016209:Interleukin-8; D020033:Protein Isoforms; D012333:RNA, Messenger; C425312:SYNCRIP protein, human; D000071479:APOBEC-1 Deaminase; C000605089:APOBEC1 protein, human; D003564:Cytidine Deaminase
keywords: Cytokine; RNA Abundance; RNA-Protein Interaction; RNA-binding Protein; Ribonuclear Protein (RNP)
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