chromomycin-a3 and hedamycin

Adjacent binding sites for early growth response factor-1 (EGR1) and TATA box-binding protein (TBP) were identified on the herpes simplex virus latency promoter in previous work. The binding of EGR1 to the GC-rich region prevented TBP binding to the AT-rich region. With the simultaneous addition of both EGR1 and TBP, the intercalator nogalamycin prevented EGR1 complex formation, resulting in a dose-dependent increase of the TBP.DNA complex. The minor groove binder chromomycin A3 inhibited EGR1 complex formation but resulted in a smaller increase of the TBP complex. In contrast, an alkylating intercalator hedamycin strongly inhibited binding of both proteins. The ability of these GC-binding drugs to prevent EGR1.DNA complex formation was in the following order: hedamycin > nogalamycin > chromomycin A3, and the specificity was nogalamycin > chromomycin A3 > hedamycin. With transcription factor IIA (TFIIA) in the assay, TBP was able to bind the promoter whereas formation of the EGR1.DNA complex was reduced. An AT minor groove-binding drug, distamycin A, disrupted the TBP.TFIIA.DNA complex and restored the EGR1.DNA complex. We conclude that the binding motif and sequence preference of DNA-interactive drugs are manifested in their ability to inhibit the transcription factor-DNA complexes.

Topics: Alkylating Agents; Anthraquinones; Base Composition; Chromomycin A3; Deoxyribonucleoproteins; Distamycins; DNA-Binding Proteins; Early Growth Response Protein 1; Gene Expression Regulation, Viral; Humans; Immediate-Early Proteins; Intercalating Agents; Macromolecular Substances; Nogalamycin; Promoter Regions, Genetic; Recombinant Fusion Proteins; Simplexvirus; TATA-Box Binding Protein; Transcription Factor TFIIA; Transcription Factors; Virus Latency