The effects of polyribonucleotides on the binding of dexamethasone-receptor complex to DNA.

The ability of polyribonucleotides to affect the association of [3H]-Dexamethasone-receptor complex with DNA-cellulose has been investigated. Certain ribopolymers can release the receptor complex DNA. This release is not dependent on the charge of the polymer only, but displays some specificity with regard to the base composition of the ribopolymer. Of the polyribonucleotides examined, polyguanylic acid and polyxanthylic acid were most effective at promoting release of the steroid-receptor from the DNA. Polyadenylic acid and polycytidylic acid had no effect on the association. For a polymer to display activity it must possess a base with an oxygen or sulfur atom at the C-6 position of purines or C-4 position of pyrimidines. Simple nucleotides possessing this structural feature are inactive.