title: Kaposi's sarcoma-associated herpesvirus latent protein LANA interacts with HIF-1 alpha to upregulate RTA expression during hypoxia: Latency control under low oxygen conditions.
abstract: Hypoxia can induce lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) in primary effusion lymphoma (PEL) cells. However, the molecular mechanism of lytic reactivation of KSHV by hypoxia remains unclear. Here we show that the latency-associated nuclear antigen (LANA), which plays a crucial role in modulating viral and cellular gene expression, directly associated with a low oxygen responder, hypoxia-inducible factor-1 alpha (HIF-1 alpha). LANA enhanced not only the transcriptional activities of HIF-1 alpha but also its mRNA level. Coimmunoprecipitation and immunofluorescence studies documented a physical interaction between LANA and HIF-1 alpha in transiently transfected 293T cells as well as in PEL cell lines during hypoxia. Through sequence analysis, several putative hypoxia response elements (HRE-1 to -6) were identified in the essential lytic gene Rta promoter. Reporter assays showed that HRE-2 (-1130 to -1123) and HRE-5 and HRE-6 (+234 to +241 and +812 to +820, respectively, within the intron sequence) were necessary and sufficient for the LANA-mediated HIF-1 alpha response. Electrophoretic mobility shift assays showed HIF-1 alpha-dependent binding of a LANA protein complex specifically to the HRE-2, -5, and -6 motifs within the promoter regulatory sequences. This study demonstrates that hypoxia-induced KSHV lytic replication is mediated at least in part through cooperation of HIF-1 alpha with LANA bound to the HRE motifs of the Rta promoter.
authors.affiliation: Department of Microbiology and the Tumor Virology Program, Abramson Comprehensive Cancer Center, University of Pennsylvania Medical School, 201E Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA, USA.
authors.forename: Qiliang
authors.initials: Q
authors.lastname: Cai
authors.forename: Ke
authors.initials: K
authors.lastname: Lan
authors.forename: Subhash C
authors.initials: SC
authors.lastname: Verma
authors.forename: Huaxin
authors.initials: H
authors.lastname: Si
authors.forename: Doug
authors.initials: D
authors.lastname: Lin
authors.forename: Erle S
authors.initials: ES
authors.lastname: Robertson
mesh_terms: D000693:Anaerobiosis / Q000235:genetics; D000956:Antigens, Viral / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D019288:Herpesvirus 8, Human / Q000235:genetics / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D017874:Immediate-Early Proteins / Q000235:genetics*; D009687:Nuclear Proteins / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics*; D014779:Virus Replication / Q000235:genetics
chemical_list: D000956:Antigens, Viral; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; C417604:Rta protein, Human herpesvirus 8; D015534:Trans-Activators; D014764:Viral Proteins; C109540:latency-associated nuclear antigen; D010100:Oxygen