SPECIFIC DNA-BINDING OF THE 2 CHICKEN DEFORMED FAMILY HOMEODOMAIN PROTEINS, CHOX-1.4 AND CHOX-A

The cDNA clones encoding two chicken Deformed (Dfd) family homeobox containing genes Chox-1.4 and Chox-a were isolated. Comparison of their amino acid sequences with another chicken Dfd family homeodomain protein and with those of mouse homologues revealed that strong homologies are located in the amino terminal regions and around the homeodomains. Although homologies in other regions were relatively low, some short conserved sequences were also identified. E. coli-made full length proteins were purified and used for the production of specific antibodies and for DNA binding studies. The binding profiles of these proteins to the 5′-leader and 5′-upstream sequences of Chox-1.4 and Chox-a coding regions were analyzed by immunoprecipitation and DNase I footprint assays. These two Chox proteins bound to the same sites in the 5′-flanking sequences of their coding regions with various affinities and their binding affinities to each site were neady the same. The consensus sequences of the high and low affinity binding sites were TAATGA(C/G) and CTAATTTT, respectively. A clustered binding stte was identified in the 5′-upstream of the Chox-a gene, suggesting that this clustered binding site works as a cis-regulatory element for auto- and/or cross-regulation of Chox-a gene expression. © 1990 Oxford University Press.