A high-throughput fluorescence-anisotropy screen that identifies small molecule inhibitors of the DNA binding of B-ZIP transcription factors

We have developed a high-throughput fluorescence anisotropy screen, using a 384-well format, to identify small molecules that disrupt the DNA binding of B-ZIP proteins. Binding of a B-ZIP dimer to fluorescently labeled DNA can be monitored by fluorescence anisotropy. We screened the National Cancer Institute diversity, set of 1990 compounds to identify small molecules that disrupt the B-ZIP vertical bar DNA coniplex of CREB, C/EBP beta, VBP, and AP-1 (FOS vertical bar JUND) bound to their cognate DNA sequence. We identified 21 compounds that inhibited the DNA binding of at least one B-ZIP Protein, and 12 representative compounds were grouped depending on whether they displaced ethidium bromide from DNA. Of the 6 compounds that did not displace ethidium bromide. 2 also inhibited B-ZIP binding to DNA in a secondary electrophoretic niobility shift assay screen with some specificity. Thermal stability monitored by circular dichroism spectroscopy demonstrated that both compounds bound the basic region of the B-ZIP motif. NSC13778 preferentially binds C/EBP alpha of 1000-fold better than it binds C/EBP beta. Chimeric proteins combining C/EBP alpha. and C/EBP beta mapped the binding of NSC13778 to three amino acids immediately N terminal of the leucine zipper of C/EBP alpha.. These experiments suggest that the DNA binding of B-ZIP transcription factors is a potential target for clinical intervention. Published by Elsevier Inc.