Genetic analysis of the cofactor requirement for human immunodeficiency virus type 1 Tat function.
The Tat protein of human immunodeficiency virus type 1 is a potent transcriptional trans activator of the viral long terminal repeat promoter element. Tat function requires the direct interaction of Tat with a cis-acting viral RNA target sequence termed the trans-activation response (TAR) element and has also been proposed to require at least one cellular cofactor. We have used a genetic approach to attempt to experimentally define the role of the cellular cofactor in Tat function and TAR binding. Our data suggest that neither Tat nor the cellular cofactor binds to TAR alone in vivo and indicate, instead, that the interaction of Tat with its cellular cofactor is a prerequisite for TAR binding. The known species tropism of lentivirus Tat proteins appears to arise from the fact that not only Tat but also the cellular cofactor can markedly influence the RNA sequence specificity of the resultant protein complex. These data also suggest that the Tat cofactor is likely a cellular transcription factor that has been highly conserved during vertebrate evolution. We hypothesize that the primary function of Tat is to redirect this cellular factor to a novel viral RNA target site and to thereby induce activation of viral gene expression.
Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
S J
SJ
Madore
B R
BR
Cullen
D000595:Amino Acid Sequence; D001483:Base Sequence; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000502:physiology*; D016325:HIV Long Terminal Repeat / Q000235:genetics*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D004860:Infectious Anemia Virus, Equine / Q000235:genetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D012367:RNA, Viral / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D013045:Species Specificity; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D046911:Macromolecular Substances; D012367:RNA, Viral; D014157:Transcription Factors; D054322:tat Gene Products, Human Immunodeficiency Virus