Interaction of 4′-6-diamidino-2-phenylindole to nucleic acids, and its implication to their template activity in RNA-polymerase reaction of E. coli bacteria and of friend-virus infected mouse spleen

Abstract

Summary The interaction between 4′-6-diamidino-2-phenylindole-dihydrochloride (DAPI) and a variety of DNAs and synthetic polydeoxynucleotides was investigated in order to delineate the nucleic acid structural features necessary for binding. The data presented here suggest that DAPI interacts preferentially to dAT-rich sites of DNA. Interestingly, the drug exhibits a very high affinity towards the hybrid polymer, poly (rA) · poly (dT). The preferential binding of DAPI to dAT-rich sites of DNA was also observed in our enzymatic studies. The inhibitory effect of DAPI on the RNA-polymerase reaction of bacterial cells was strictly dependent on the base composition of the template used. This inhibition is of competitive type, as evidenced by the Lineweaver-Burk plots of the kinetic data. Studies with RNA-polymerases I and II of the nuclei from FLV-infected mouse spleen revealed that the inhibitory effect of DAPI in both the systems was similar. The drug : DNA ratio ( r ) required to inhibit 50% of the enzyme activity was identical for both the systems.