Human foamy virus genome possesses an internal, Bel-1-dependent and functional promoter.
The human foamy or spumaretrovirus (HSRV) is a complex retrovirus that encodes the three retroviral genes gag, pol, and env and, in addition, at least three bel genes. The HSRV Bel-1 protein was identified as a transcriptional trans-activator. HSRV transcription starts in the 5' long terminal repeat at a defined guanine residue. We report here that a second efficiently utilized start site of transcription is contained within a HSRV env DNA sequence upstream of the bel genes. Bel-specific transcripts that initiate at the internal transcriptional start site at nt 9196 were identified in HSRV-infected cells by primer extension and S1 nuclease analysis, and the intragenic promoter was shown to be constitutively activated by Bel-1 in the HSRV provirus. In transient expression assays with indicator gene constructs, expression by the HSRV intragenic promoter/enhancer is Bel-1 dependent. The data provide evidence for an intragenic start site of transcription in the genome of a complex, exogenous human retrovirus and are discussed in terms of a model for regulating spumaretroviral gene expression.
Abteilung Retrovirale Genexpression, Forschungsschwerpunkt Angewandte Tumorvirologie, Heidelberg, Federal Republic of Germany.
M
M
Löchelt
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W
Muranyi
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RM
Flügel
D001483:Base Sequence; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D015752:Genes, env; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D012191:Retroviridae Proteins / Q000235:genetics*; D016092:Spumavirus / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D015678:Viral Structural Proteins / Q000235:genetics*
D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D012367:RNA, Viral; D012191:Retroviridae Proteins; D015534:Trans-Activators; D015678:Viral Structural Proteins; C074061:bel1 protein, Human foamy virus