Tat transactivation of the human immunodeficiency virus type 1 promoter is influenced by basal promoter activity and the simian virus 40 origin of DNA replication.
We examined the activation of transcription from the human immunodeficiency virus type 1 (HIV-1) promoter by the viral Tat protein in a transient expression system. Plasmids contained a HIV-reporter gene cassette and a simian virus 40 origin of DNA replication. Run-on assays of transcription complex distribution and analysis of cytoplasmic RNA accumulation confirmed that Tat is able to activate transcription by two mechanisms: by increasing the rate of transcriptional initiation and the efficiency of transcriptional elongation. The degree to which Tat stimulated initiation is determined by the basal level of HIV-directed transcription, which is influenced by the presence [corrected] of the simian virus 40 replication origin. Tat functions primarily to increase the efficiency of elongation when the origin is present and the basal level of transcription is high [corrected]. On the other hand, Tat functions primarily to increase the rate of initiation when the origin is absent [corrected] and the basal level of transcription is 10-fold lower. These studies suggest that the site of integration of the virus into the cellular genome may significantly affect the level of expression from the HIV promoter and consequently the pathobiology of the virus.
Kessler
M
M
Cold Spring Harbor Laboratory, NY 11724-2208.
Mathews
M B
MB
D000818:Animals; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004279:DNA, Viral / Q000032:analysis / Q000235:genetics; D015696:Gene Products, tat / Q000378:metabolism*; D005814:Genes, Viral; D005822:Genetic Vectors; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D007700:Kinetics; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D013539:Simian virus 40 / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D054322:tat Gene Products, Human Immunodeficiency Virus
D004279:DNA, Viral; D015696:Gene Products, tat; D011994:Recombinant Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D015500:Chloramphenicol O-Acetyltransferase