These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Role of flanking E box motifs in human immunodeficiency virus type 1 TATA element function.
    Author: Ou SH, Garcia-Martínez LF, Paulssen EJ, Gaynor RB.
    Journal: J Virol; 1994 Nov; 68(11):7188-99. PubMed ID: 7933101.
    Abstract:
    Human immunodeficiency virus type 1 (HIV-1) gene expression is dependent on a number of cis-acting DNA elements present in the HIV-1 long terminal repeat. Previous studies have demonstrated that the TATA element is critical for basal and Tat-induced HIV-1 gene expression. The HIV-1 TATA region has an unusual structure in that the TATA sequence is flanked by two palindromic sequence motifs (CANNTG) known as E boxes which can serve as binding sites for the basic helix-loop-helix (bHLH) class of DNA-binding proteins. In this study, we performed site-directed mutagenesis of both the TATA and the flanking E box sequences of HIV-1. We also substituted the sequences flanking the adenovirus E3 promoter TATA sequence for those flanking the HIV-1 TATA sequence. Constructs were assayed for their levels of basal and Tat-induced gene expression by both in vitro transcription and transient expression assays. Both the TATA box and flanking sequences including the E box motifs were found to be important in modulating both basal gene expression and Tat-induced HIV-1 gene expression. Gel retardation analysis demonstrated that binding of both the recombinant TATA-binding protein (TBP) and the TFIID fraction which contains both TBP and TBP-associated factors was dependent primarily on the TATA element. However, competition analysis suggested that the E boxes may play a role in stabilizing the binding of TFIID but not recombinant TBP. Two proteins representing different classes of bHLH proteins, E47 and AP-4, were assayed for their ability to bind to the flanking E box motifs. We isolated a cDNA clone encoding the complete AP-4 protein and demonstrated that both AP-4 and E47 bound specifically to the 3' E box motif, which contains sequences that correspond to the consensus binding site (CAGCTG). Gel retardation analysis indicated that the binding of AP-4 to the E boxes excluded the binding of TBP to the TATA box. These studies are consistent with a model in which different classes of cellular bHLH proteins may be involved in regulating HIV-1 TATA element function by either inhibiting or promoting the assembly of different preinitiation transcriptional complexes.
    [Abstract] [Full Text] [Related] [New Search]