title: Control of the negative IRES trans-acting factor KHSRP by ubiquitination.
abstract: Cells and viruses can utilize internal ribosome entry sites (IRES) to drive translation when cap-dependent translation is inhibited by stress or viral factors. IRES trans-acting factors (ITAFs) are known to participate in such cap-independent translation, but there are gaps in the understanding as to how ITAFs, particularly negative ITAFs, regulate IRES-driven translation. This study found that Lys109, Lys121 and Lys122 represent critical ubiquitination sites for far upstream element-binding protein 2 (KHSRP, also known as KH-type splicing regulatory protein or FBP2), a negative ITAF. Mutations at these sites subsequently reduced KHSRP ubiquitination and abolished its inhibitory effect on IRES-driven translation. We further found that interaction between the Kelch domain of Kelch-like protein 12 (KLHL12) and the C-terminal domain of KHSRP contributed to KHSRP ubiquitination, leading to downregulation of enterovirus IRES-mediated translation in infected cells and increased competition against other positive ITAFs. Together, these results show that ubiquitination can exert control over IRES-driven translation via modification of ITAFs, and to the best of our knowledge, this is the first description of such a regulatory mechanism for IRES-dependent translation.
authors.affiliation: Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Taoyuan City 33302, Taiwan.|Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan City 33302, Taiwan.
authors.forename: Yu-An
authors.initials: YA
authors.lastname: Kung
authors.affiliation: Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Taoyuan City 33302, Taiwan.|Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan City 33302, Taiwan.
authors.forename: Chuan-Tien
authors.initials: CT
authors.lastname: Hung
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Medicine, Chang Gung University, Taoyuan City 33302, Taiwan.|Clinical Proteomics Core Laboratory, Linkou Chang Gung Memorial Hospital, Taoyuan City 33305, Taiwan.
authors.forename: Kun-Yi
authors.initials: KY
authors.lastname: Chien
authors.affiliation: Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Taoyuan City 33302, Taiwan srshih@mail.cgu.edu.tw.|Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan City 33302, Taiwan.|Clinical Virology Laboratory, Department of Laboratory Medicine, Chang Gung Memorial Hospital, Taoyuan City 33305, Taiwan.
authors.forename: Shin-Ru
authors.initials: SR
authors.lastname: Shih
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D045744:Cell Line, Tumor; D004770:Enterovirus / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D000067556:Internal Ribosome Entry Sites; D008239:Lysine / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D032342:Muscle Cells / Q000378:metabolism* / Q000821:virology; D009154:Mutation; D014176:Protein Biosynthesis; D000072417:Protein Domains; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000067556:Internal Ribosome Entry Sites; C105789:KHSRP protein, human; C493279:KLHL12 protein, human; D008840:Microfilament Proteins; D016601:RNA-Binding Proteins; D015534:Trans-Activators; D008239:Lysine