Structural requirements for trans activation of human immunodeficiency virus type 1 long terminal repeat-directed gene expression by tat: importance of base pairing, loop sequence, and bulges in the tat-responsive sequence.
In order to elucidate the molecular mechanisms of action of the tat-responsive sequence, mutational analysis of the tat-responsive sequence was carried out. The most critical region comprised nucleotides +18 to +44 and included the 3-nucleotide bulge at positions +23 to +25, the loop sequence, and an intact stem. In addition, base pairing up to nucleotide +52 was required for the full magnitude of the trans-activation response. Single-nucleotide bulges at positions +5 to +17 were dispensable. Analysis of truncated and full-length transcripts demonstrated that a transcriptional antitermination model does not fully account for trans activation.
Department of Biochemistry, McGill University, Montreal, Canada.
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S
Roy
N T
NT
Parkin
C
C
Rosen
J
J
Itovitch
N
N
Sonenberg
D001482:Base Composition; D001483:Base Sequence; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000378:metabolism*; D005814:Genes, Viral; D015497:HIV-1 / Q000235:genetics*; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012260:Ribonucleases; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D012333:RNA, Messenger; D015534:Trans-Activators; D054322:tat Gene Products, Human Immunodeficiency Virus; D012260:Ribonucleases