ACRIDINE-LABELED PRIMERS AS TOOLS FOR THE STUDY OF NONENZYMATIC RNA OLIGOMERIZATION

Short, dye-labeled oligonucleotides have been used as primers in templ ate-controlled polymerization reactions of RNA. The synthesis of appro priate acridine derivatives and their attachment to nucleic acids is d escribed. In the nonenzymatic oligomerization of 2-methyl-1H-imidazole -activated guanosine SI-monophosphate, two observations deserve specia l notice: 1) reaction rates are almost unchanged by variations of the Na+ concentration; 2) the conformational type of the primer-template d uplex (A vs. B) has considerable influence on the rates and yields of RNA oligomerization. When the incorporation of cytidine was studied in the presence of 1 M Na+ or K+. the process was almost inhibited by qu adruples formation of the oligo-dG template. However, if these cations were omitted, an efficient primer extension could be observed using t emplate concentrations as high as 100 mu M. The chances for nonenzymat ic self-replication of RNA thus might be distinctly better than previo usly assumed.