Glucocorticoid receptor-steroid complex binding to DNA. Competition between DNA and DNA-cellulose

The binding of the glucocorticoid receptor-steroid complex from a line of rat hepatoma tissue culture (HTC) cells to DNA has been examined. An equilibrium competition assay involving a constant, low total amount of double-stranded DNA was developed to compare the complex binding ability of DNA free in solution and bound to cellulose. This binding ability is lowered by a factor of five when DNA is associated with cellulose. Similar studies with HTC cell, calf-thymus, and Escherichia coli DNA revealed no difference in the relative number or affinity of binding sites for receptor-steroid complex in each DNA. The synthetic DNA molecules poly[d(A-T)-d(A-T)] and poly[d(G-C)-d(G-C)] bound complexes equally well but less than the three "natural" DNA molecules. This appears to be due to differences in acceptor site affinity and suggests that nucleotide complexity and/or sequence influences the affinity of HTC cell receptor-glucocorticoid complexes for DNA.