Identification of the immediate-early transcripts of Kaposi's sarcoma-associated herpesvirus.
In the immediate-early phase of reactivation or primary infection, herpesviruses express a small number of genes without requiring prior viral protein synthesis. Immediate-early genes usually encode regulatory proteins critical for the viral life cycle. Kaposi's sarcoma-associated herpesvirus (KSHV) gene transcription in the immediate-early stage of viral reactivation was examined by using a chemical induction combined with a gene expression screening method. RNA transcripts from at least four KSHV genomic loci accumulate when latently infected B-lymphoma cells are induced for reactivation in the presence of an inhibitor of protein synthesis (cycloheximide) and thus represent immediate-early class transcripts. Among them, a 3.6-kb mRNA encodes three putative open reading frames (ORFs), namely, ORF50, K8, and K8.2. ORF50 is a homologue of Rta, a transcription activator encoded by Epstein-Barr virus (EBV). The K8 gene codes for a 237-amino-acid protein with a basic-leucine zipper domain near its C terminus and an acidic domain near its N terminus and which closely resembles the ZEBRA protein of EBV and Jun/Fos family proteins. Other immediate-early mRNAs of KSHV include a 1. 7-kb mRNA encoding ORF45, a 2.0-kb mRNA encoding ORF K4.2, and a 4. 5-kb mRNA. Functional roles of products of these KSHV immediate-early transcripts remain to be studied.
Zhu
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Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania 19104, USA.
Cusano
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Yuan
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D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D018076:DNA, Complementary; D004279:DNA, Viral; D015967:Gene Expression Regulation, Viral; D017781:Genes, Immediate-Early; D005814:Genes, Viral; D019288:Herpesvirus 8, Human / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D012333:RNA, Messenger; D012107:Research Design; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D004279:DNA, Viral; D012333:RNA, Messenger