Transcriptional activation of homologous viral long terminal repeats by the human immunodeficiency virus type 1 or the human T-cell leukemia virus type I tat proteins occurs in the absence of de novo protein synthesis.
The genomes of human retroviruses [human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus (HTLV-I)] encode positive trans-activator proteins, named tat. In the presence of tat, the transcriptional activity of the homologous HIV-1 or HTLV-I long terminal repeat (LTR) promoter is markedly increased. We have constructed mammalian cell lines that contain stably integrated copies of a HIV-1 or a HTLV-I LTR-chloramphenicol acetyltransferase (CAT) gene. When presynthesized HIV-1 or HTLV-I tat proteins were separately introduced into these cells in the presence of cycloheximide, we found a strong increase in the steady-state expression of the homologous viral LTR. Nuclear "run-on" assays verified that this tat-mediated enhancement, occurring in the absence of de novo cellular protein synthesis, was due to increased transcriptional initiation at the LTR promoter. We conclude that one aspect of transcriptional trans-activation of viral LTR by the HIV-1 and HTLV-I tat proteins does not require the production of new cellular proteins.
Jeang
K T
KT
Laboratory of Molecular Virology, National Cancer Institute, Bethesda, MD 20892.
Shank
P R
PR
Kumar
A
A
D000818:Animals; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D015696:Gene Products, tat; D015497:HIV-1 / Q000235:genetics*; D008970:Molecular Weight; D014176:Protein Biosynthesis; D012091:Repetitive Sequences, Nucleic Acid; D014157:Transcription Factors / Q000494:pharmacology*; D014158:Transcription, Genetic; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D014157:Transcription Factors; D054322:tat Gene Products, Human Immunodeficiency Virus