TAR-independent activation of the HIV-1 LTR: evidence that tat requires specific regions of the promoter.
Replication of HIV-1 requires Tat, which stimulates gene expression through a target sequence, TAR. It is known that TAR is a Tat-responsive target. Since Tat increases transcriptional initiations from the HIV-1 LTR promoter, it is unclear mechanistically how Tat utilizes an RNA target. Here we show that TAR RNA is only one component of the Tat-responsive target. Efficient Tat trans-activation was observed only when TAR was present in conjunction with the HIV-1 LTR NF-kappa B/SP1 DNA sequences. TAR RNA outside of this context produced a suboptimal Tat response. We propose that TAR RNA serves an attachment function directing Tat to the LTR. A Tat protein engineered to interact with LTR DNA could trans-activate through a TAR-independent mechanism. This suggests that Tat also has a DNA target.
Berkhout
B
B
Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Gatignol
A
A
Rabson
A B
AB
Jeang
K T
KT
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004252:DNA Mutational Analysis; D004279:DNA, Viral / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000502:physiology*; D015497:HIV-1 / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012367:RNA, Viral / Q000235:genetics; D011993:Recombinant Fusion Proteins; D012045:Regulatory Sequences, Nucleic Acid; D015534:Trans-Activators / Q000502:physiology*; D014158:Transcription, Genetic; D054322:tat Gene Products, Human Immunodeficiency Virus
D004279:DNA, Viral; D015696:Gene Products, tat; D012367:RNA, Viral; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D054322:tat Gene Products, Human Immunodeficiency Virus