title: Kaposi's sarcoma-associated herpesvirus latency-associated nuclear antigen induction by hypoxia and hypoxia-inducible factors.
abstract: Hypoxia and hypoxia-inducible factors (HIFs) play an important role in the Kaposi's sarcoma-associated herpesvirus (KSHV) life cycle. In particular, hypoxia can activate lytic replication of KSHV and specific lytic genes, including the replication and transcription activator (RTA), while KSHV infection in turn can increase the levels and activity of HIFs. In the present study, we show that hypoxia increases the levels of mRNAs encoding KSHV latency-associated nuclear antigen (LANA) in primary effusion lymphoma (PEL) cell lines and also increases the levels of LANA protein. Luciferase reporter assays in Hep3B cells revealed a moderate activation of the LANA promoter region by hypoxia as well as by cotransfection with degradation-resistant HIF-1α or HIF-2α expression plasmids. Computer analysis of a 1.2-kb sequence upstream of the LANA translational start site identified six potential hypoxia-responsive elements (HRE). Sequential deletion studies revealed that much of this activity was mediated by one of these HREs (HRE 4R) oriented in the 3' to 5' direction and located between the constitutive (LTc) and RTA-inducible (LTi) mRNA start sites. Site-directed mutation of this HRE substantially reduced the response to both HIF-1α and HIF-2α in a luciferase reporter assay. Electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP) assays demonstrated binding of both HIF-1α and HIF-2α to this region. Also, HIF-1α was found to associate with RTA, and HIFs enhanced the activation of LTi by RTA. These results provide evidence that hypoxia and HIFs upregulate both latent and lytic KSHV replication and play a central role in the life cycle of this virus.
authors.affiliation: HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA.
authors.forename: Ravindra P
authors.initials: RP
authors.lastname: Veeranna
authors.forename: Muzammel
authors.initials: M
authors.lastname: Haque
authors.forename: David A
authors.initials: DA
authors.lastname: Davis
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: Robert
authors.initials: R
authors.lastname: Yarchoan
mesh_terms: D000956:Antigens, Viral / Q000235:genetics* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D015967:Gene Expression Regulation, Viral; D019288:Herpesvirus 8, Human / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020218:Response Elements; D012514:Sarcoma, Kaposi / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D015533:Transcriptional Activation; D015854:Up-Regulation; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D000956:Antigens, Viral; D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C109540:latency-associated nuclear antigen
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