BINDING OF PHOSPHOROTHIOATE OLIGODEOXYNUCLEOTIDES TO BASIC FIBROBLASTGROWTH-FACTOR, RECOMBINANT SOLUBLE CD4, LAMININ AND FIBRONECTIN IS P-CHIRALITY INDEPENDENT

Antisense oligodeoxynucleotides can selectively inhibit the expression of individual genes and thus have potential applications in anticance r and antiviral therapy, A critical prerequisite to their use as thera peutic agents is the understanding of their non-specific interactions with biological structures, e.g. proteins, In this study we examined t he interactions of P-chiral phosphorothioate oligodeoxynucleotides wit h several proteins, The Rp- and Sp- diastereomers, and racemic machine -made mixtures, or M-oligodeoxynucleotides were used independently as competitors of the binding of a probe, phosphodiester oligodeoxynucleo tide bearing a 5' alkylating moiety, to rsCD4, bFGF and laminin, These oligodeoxynucleotides were also used as competitors of the binding of a non-alkylating probe M-phosphorothioate oligodeoxynucleotide, 5'-P- 32-SdT(18) to fibronectin, The average values of and quantitative esti mates for the IC50 of competition and the constant of competition (K-c ) of Rp-, Sp- and M- stereoisomers of several homo- and heteropolymer oligodeoxynucleotides were determined and compared, Surprisingly, in t he proteins we studied, the values of IC50 and K-c for the Rp-, Sp- an d M-oligodeoxynucleotides were essentially identical, Thus, the abilit y of the phosphorethioate oligodeoxynucleotides we employed, to bind t o the proteins studied in this work, is virtually independent of P-chi rality, Our results also imply that the role of the purine and pyrimid ine bases in oligodeoxynucleotide-protein interactions, as well as the nature of the contact points (sulfur versus oxygen) between the oligo mer and the protein, may be relatively unimportant.