title: Kaposi's sarcoma-associated herpesvirus ORF57 promotes escape of viral and human interleukin-6 from microRNA-mediated suppression.
abstract: Kaposi's sarcoma-associated herpesvirus (KSHV) lytic infection increases the expression of viral and human interleukin-6 (vIL-6 and hIL-6, respectively), an important factor for cell growth and pathogenesis. Here, we report genome-wide analysis of viral RNA targets of KSHV ORF57 by a novel UV-cross-linking and immunoprecipitation (CLIP) assay. We identified 11 viral transcripts as putative ORF57 targets and demonstrate that vIL-6 mRNA is an authentic target of ORF57. Disrupting the ORF57 gene in the KSHV genome leads to inefficient expression of vIL-6. With transient transfection, the expression of vIL-6 could be enhanced greatly in the presence of ORF57 in a dose-dependent manner. We found that the open reading frame (ORF) region of vIL-6 RNA contains an MRE (MTA [ORF57]-responsive element) composed of two motifs, MRE-A and MRE-B, and binding of ORF57 to these two motifs stabilizes vIL-6 RNA and promotes vIL-6 translation. We demonstrate that vIL-6 MRE-B bears an miR-1293 binding site and that, mechanistically, ORF57 competes with miR-1293 for the same binding site to interact with vIL-6 RNA, thereby preventing vIL-6 RNA from association with the miR-1293-specified RNA-induced silencing complex (RISC). Consistent with this, ORF57 also interacts with an miR-608 binding site in the hIL-6 ORF and prevents miR-608 repression of hIL-6. Collectively, our results identify a novel function of ORF57 in being responsible for stabilization of viral and human IL-6 RNAs and the corresponding enhancement of RNA translation. In addition, our data provide the first evidence that a tumor virus may use a viral protein to interfere with microRNA (miRNA)-mediated repression of an miRNA target to induce cell proliferation and tumorigenesis during virus infection.
authors.affiliation: Tumor Virus RNA Biology Laboratory, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, 10 Center Dr., Rm. 6N106, Bethesda, MD 20892-1868, USA.
authors.forename: Jeong-Gu
authors.initials: JG
authors.lastname: Kang
authors.forename: Natalia
authors.initials: N
authors.lastname: Pripuzova
authors.forename: Vladimir
authors.initials: V
authors.lastname: Majerciak
authors.forename: Michael
authors.initials: M
authors.lastname: Kruhlak
authors.forename: Shu-Yun
authors.initials: SY
authors.lastname: Le
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Zheng
mesh_terms: D002460:Cell Line; D019288:Herpesvirus 8, Human / Q000276:immunology / Q000472:pathogenicity*; D006801:Humans; D057131:Immune Evasion; D047468:Immunoprecipitation; D015850:Interleukin-6 / Q000378:metabolism*; D035683:MicroRNAs / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011485:Protein Binding; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D015850:Interleukin-6; D035683:MicroRNAs; D014764:Viral Proteins