Effects of varying lengths of double-stranded RNA on binding and activation of 2'-5'-oligoadenylate synthetase.

We investigated the effects of varying the length of the double-stranded (ds) RNA cofactor on activation of 2'-5'-oligoadenylate [2-5 (A)] synthetase. dsRNA of 40, 55, 67, 85, and 110 bp lengths were generated by in vitro transcription of complementary strands and annealing and trimming of the single-stranded overhangs. The dsRNA molecules were radiolabeled by polynucleotide kinase and purified by gel electrophoresis. Their abilities to bind to recombinant mouse 9-2 2-5 (A) synthetase, as monitored by electrophoretic mobility shift assays, were comparable. When used at a saturating concentration of 25 microg/ml, all dsRNA molecules were equally effective in activating the enzyme. At a subsaturating concentration, however, longer RNAs were better activators. At 100 nM concentration, there was a linear relationship between the length of the dsRNA and its ability to activate 2-5 (A) synthetase.