Activation of a heterologous promoter by human immunodeficiency virus type 1 Tat requires Sp1 and is distinct from the mode of activation by acidic transcriptional activators.
We have previously shown that the Tat protein of the human immunodeficiency virus type 1 (HIV-1) is a modular transcriptional activator that can be targeted upstream of either a synthetic promoter or the intact HIV promoter to activate transcription. This activation was shown to be largely dependent on the presence of consensus binding sites for the cellular transcription factor Sp1. Since the use of heterologous promoters may provide further insight into Tat-mediated transactivation, we have analyzed the transactivation of the thymidine kinase promoter of herpes simplex virus by Tat and by the acidic transcriptional transactivator VP16. The effects of mutations of defined upstream promoter elements show that Tat transactivation is dependent on Sp1 binding sites in a site-specific manner. In contrast, transactivation by the acidic transactivator VP16 is completely independent of any of the defined promoter elements upstream of the TATA box. These results suggest that Tat and the classically defined modular acidic transcriptional activators have different modes of transactivation. In addition, the substitution of the HIV-1 TATA box for the thymidine kinase TATA box substantially increases Tat transactivation, indicating that Tat transactivation may also ultimately involve TATA box-associated cellular transcription factors.
Kamine
J
J
Institute for Molecular Virology, St. Louis University School of Medicine, Missouri 63110.
Subramanian
T
T
Chinnadurai
G
G
D001483:Base Sequence; D005656:Fungal Proteins / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000235:genetics*; D015497:HIV-1 / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000235:genetics*; D013329:Structure-Activity Relationship; D016385:TATA Box; D013937:Thymidine Kinase / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus
D005656:Fungal Proteins; C070633:Gal-VP16; D015696:Gene Products, tat; D016329:Sp1 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; D054322:tat Gene Products, Human Immunodeficiency Virus; D013937:Thymidine Kinase