A cooperative interaction between NF-kappa B and Sp1 is required for HIV-1 enhancer activation.

Abstract

The human immunodeficiency virus (HIV‐1) long terminal repeat (LTR) contains two binding sites for NF‐kappa B in close proximity to three binding sites for the constitutive transcription factor, Sp1. Previously, stimulation of the HIV enhancer in response to mitogens has been attributed to the binding of NF‐kappa B to the viral enhancer. In this report, we show that the binding of NF‐kappa B is not by itself sufficient to induce HIV gene expression. Instead, a protein‐protein interaction must occur between NF‐kappa B and Sp1 bound to an adjacent site. Cooperativity both in DNA binding and in transcriptional activation of NF‐kappa B and Sp1 was confirmed by electrophoretic mobility shift gel analysis, DNase footprinting, chemical cross‐linking and transfection studies in vivo. With a heterologous promoter, we find that the interaction of NF‐kappa B with Sp1 is dependent on orientation and position, and is not observed with other elements, including GATA, CCAAT or octamer. An increase in the spacing between the kappa B and Sp1 elements virtually abolishes this functional interaction, which is not restored when these sites are brought back into the same helical position. Several other promoters regulated by NF‐kappa B also contain kappa B in proximity to Sp1 binding sites. These findings suggest that an interaction between NF‐kappa B and Sp1 is required for inducible HIV‐1 gene expression and may serve as a regulatory mechanism to activate specific viral and cellular genes.

In vitro evaluation of cancer-specific NF-κB-CEA enhancer–promoter system for 5-fluorouracil prodrug gene therapy in colon cancer cell lines

“…Therefore, we also tested the potential transcriptional leakage of the NF-kB-CEA enhancer -promoter system. In agreement with a previous report (Perkins et al, 1993), the NF-kB-binding sites by itself, as an enhancer element, only possessed very low transcriptional activity. The transcriptional activity in cancer cell lines was highly increased by the combination of kB4 and CEA promoter and meanwhile the cancer-targeting specificity was still remained ( Figure 3A and C and Table 1).…”

“…Mutation of the adjacent kB and Sp1 DNA-binding sites completely abolishes the phorbol myristate acetate inducible transcriptional activity (Perkins et al, 1993). It was also reported that an Sp1-dependent promoter is distantly enhanced by an NF-kB enhancer (Teferedegne et al, 2006).…”

“…It was also reported that an Sp1-dependent promoter is distantly enhanced by an NF-kB enhancer (Teferedegne et al, 2006). The cooperation between NF-kB and Sp1 needs direct contact of both proteins and other transcription modulators (Perkins et al, 1993;Teferedegne et al, 2006). Chromatin modulation is also involved.…”

“…Although by definition, enhancer is a DNA element, which efficiently regulates promoter activity distantly and orientation-independently (Banerji et al, 1983;Sassone-Corsi et al, 1983), the relationship between enhancer and promoter elements is far more complex. A cooperative interaction between NF-kB and Sp1 has been demonstrated in human immunodeficiency virus long terminal repeat (HIV-1 LTR) promoter region (Nabel and Baltimore, 1987;Perkins et al, 1993). The cooperation between NF-kB and Sp1 in the HIV-1 LTR is highly space and orientation-dependent.…”

Activation of the wt1 Wilms' tumor suppressor gene by NF-κB

“…Such cooperativity has recently been described by Perkins et al (1993), who demonstrated that activation of the HIV-1 LTR depends on an interaction between p65 and Sp-1. Transactivation of the wt1 promoter is also positively regulated by Sp-1 (Cohen et al, 1997;Ho man et al, 1993).…”