INHIBITION OF DNA TOPOISOMERASE-I ACTIVITY BY 2',5'-OLIGOADENYLATES AND MISMATCHED DOUBLE-STRANDED-RNA IN UNINFECTED AND HIV-1-INFECTED H9 CELLS

2',5'-Oligoadenylates (2-5As) inhibit the type 1 DNA topoisomerase act ivity both in uninfected and HIV-1-infected human T cell line H9 as we ll as the purified enzyme (calf thymus). Topoisomerase I activity was determined by measuring the relaxation of negatively supercoiled pBR32 2 DNA. Inhibition of topoisomerase I by 2-5A depends on the chain leng th of the oligomer and the presence of 5' phosphate. The 5'-triphospha te of the 2-5A hexamer was most active (almost total inhibition of DNA relaxation at 10 muM concentration); the 2-5A core trimer (at 100 muM ) displayed no significant effect. In crosslinking and immunoprecipita tion experiments we present evidence that 2-5A (P-32-labelled 2-5A der ivative, ppp(A2'p)2 A[P-32]pCp) is able to bind to nuclear topoisomera se 1. The mismatched dsRNA, poly(I).poly(C12U) (Ampligen), exhibited a strong anti-HIV-1 activity. However, our data show that this antivira l effect is not related to topoisomerase I inhibition. On the other ha nd, we did observe the production of longer oligomers of 2-5A in cells treated with poly(I).poly(C12U). It remains speculative, whether the in vivo effect could be catalyzed by this activity of poly(I).poly(C12 U). In addition we could show that 2-5A also inhibits topoisomerase I activity associated with isolated HIV-1 particles.