ACTINOMYCIN-D INHIBITION OF DNA STRAND TRANSFER-REACTIONS CATALYZED BY HIV-1 REVERSE-TRANSCRIPTASE AND NUCLEOCAPSID PROTEIN

Actinomycin D was found to be a potent inhibitor of HIV-1 reverse tran scriptase catalyzed DNA strand transfer reactions. Using an oligonucle otide model system, actinomycin D inhibition of DNA strand transfer wa s examined to elucidate the mechanism of inhibition and further define the mechanism of DNA strand transfer. Our results show that actinomyc in D inhibits HIV-1 reverse transcriptase catalyzed DNA strand transfe r without inhibiting RNA-dependent or DNA-dependent DNA polymerase act ivity. Actinomycin D was found to strongly inhibit annealing of a prim ary DNA product to the DNA acceptor template, preventing the formation of a key reaction intermediate. The HIV-1 nucleocapsid protein has be en shown to participate in catalytic events during reverse transcripti on including DNA strand transfer. Recombinant nucleocapsid protein was used in conjunction with actinomycin D in this model system to invest igate how NC may participate in the mechanism of inhibition by actinom ycin D and in DNA strand transfer. The inclusion of nucleocapsid prote in was found to partially relieve both DNA annealing and strand transf er inhibition caused by actinomycin D. This study suggests a potential new mechanism for inhibiting retroviral replication by preventing the formation of replication intermediates.