title: The early gene hhi1 reactivates Heliothis zea nudivirus 1 in latently infected cells.
abstract: Heliothis zea nudivirus 1 (HzNV-1), previously known as Hz-1 virus, is an insect virus able to establish both productive and latent infections in several lepidopteran insect cells. Here, we have cloned and characterized one of the HzNV-1 early genes, hhi1, which maps to the HindIII-I fragment of the viral genome. During the productive viral infection, a 6.2-kb hhi1 transcript was detectable as early as 0.5 h postinfection (hpi). The level of transcript reached a maximum at 2 hpi and gradually decreased after 4 hpi. The transcript was not detectable during the latent phase of viral infection. Upon cycloheximide treatment, much higher levels of hhi1 transcript were detected throughout the productive viral infection cycle, suggesting that newly synthesized proteins are not needed for the expression of hhi1. Nevertheless, viral coinfection can further stimulate the expression of transfected hhi1 promoter in a plasmid. Transient hhi1 expression in latently infected cells resulted in a significant increase in virus titer and viral DNA propagation, suggesting that hhi1 plays a critical role in viral reactivation. Additional experiments showed that six early genes, which possibly function in transcription or DNA replication, were activated in the latent cells upon hhi1 transfection. Among these six genes, orf90 and orf121 expression could be induced by hhi1 alone without the need for other viral genes. Our discovery should be useful for future mechanistic study of the switches of latent/productive HzNV-1 viral infections.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, No. 128, Section 2, Nankang, Taipei 105, Taiwan, Republic of China.
authors.forename: Yueh-Lung
authors.initials: YL
authors.lastname: Wu
authors.forename: Carol P
authors.initials: CP
authors.lastname: Wu
authors.forename: Song-Tay
authors.initials: ST
authors.lastname: Lee
authors.forename: Han
authors.initials: H
authors.lastname: Tang
authors.forename: Chi-Hua
authors.initials: CH
authors.lastname: Chang
authors.forename: Hong-Hwa
authors.initials: HH
authors.lastname: Chen
authors.forename: Yu-Chan
authors.initials: YC
authors.lastname: Chao
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004267:DNA Viruses / Q000235:genetics / Q000502:physiology*; D015967:Gene Expression Regulation, Viral; D009036:Moths / Q000821:virology*; D018411:Spodoptera; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D014775:Virus Activation; D017735:Virus Latency
chemical_list: D014764:Viral Proteins