title: Kaposi's sarcoma-associated herpesvirus noncoding polyadenylated nuclear RNA interacts with virus- and host cell-encoded proteins and suppresses expression of genes involved in immune modulation.
abstract: During lytic infection, Kaposi's sarcoma-associated herpesvirus (KSHV) expresses a polyadenylated nuclear RNA (PAN RNA). This noncoding RNA (ncRNA) is localized to the nucleus and is the most abundant viral RNA during lytic infection; however, to date, the role of PAN RNA in the virus life cycle is unknown. Many examples exist where ncRNAs have a defined key regulatory function controlling gene expression by various mechanisms. Our goal for this study was to identify putative binding partners for PAN RNA in an effort to elucidate a possible function for the transcript in KSHV infection. We employed an in vitro affinity protocol where PAN RNA was used as bait for factors present in BCBL-1 cell nuclear extract to show that PAN RNA interacts with several virus- and host cell-encoded factors, including histones H1 and H2A, mitochondrial and cellular single-stranded binding proteins (SSBPs), and interferon regulatory factor 4 (IRF4). RNA chromatin immunoprecipitation (ChIP) assays confirmed that PAN RNA interacted with these factors in the infected cell environment. A luciferase reporter assay showed that PAN RNA expression interfered with the ability of IRF4/PU.1 to activate the interleukin-4 (IL-4) promoter, strongly suggesting a role for PAN RNA in immune modulation. Since the proteomic screen and functional data suggested a role in immune responses, we investigated if constitutive PAN RNA expression could affect other genes involved in immune responses. PAN RNA expression decreased expression of gamma interferon, interleukin-18, alpha interferon 16, and RNase L. These data strongly suggest that PAN RNA interacts with viral and cellular proteins and can function as an immune modulator.
authors.affiliation: University of Nevada, Reno, School of Medicine, Department of Microbiology and Immunology, 1664 N. Virginia St., Center for Molecular Medicine Building/Mailstop 320, Reno, NV 89557, USA.
authors.forename: Cyprian C
authors.initials: CC
authors.lastname: Rossetto
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Pari
mesh_terms: D000818:Animals; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D017930:Genes, Reporter; D019288:Herpesvirus 8, Human / Q000276:immunology / Q000472:pathogenicity*; D054884:Host-Pathogen Interactions; D006801:Humans; D057131:Immune Evasion; D050835:Interferon Regulatory Factors / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D015138:RNA, Nuclear / Q000378:metabolism*; D022661:RNA, Untranslated / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D050835:Interferon Regulatory Factors; D011506:Proteins; D015138:RNA, Nuclear; D022661:RNA, Untranslated; D012367:RNA, Viral; D014764:Viral Proteins; C413486:viral interferon regulatory factors; D015847:Interleukin-4; D008156:Luciferases