A study of the Topoisomerase II activity in HIV-1 replication using the ferrocene derivatives as probes

Human Topoisomerase 11 is present in two isoforms, 170 KDa alpha and 180 KDa beta. Both the isoforms play a crucial role in maintenance of topological changes during DNA replication and recombination. It has been shown that Topoisomerase 11 activity is required for HIV-1 replication and the enzyme is phosphorylated during early time points of HIV-1 replication. In the present study, we have studied the molecular action of Topoisomerase 11 inhibitors, azalactone ferrocene (AzaFecp), Thiomorpholide amido methyl ferrocene (ThioFecp), and Ruthenium benzene amino pyridine (Ru(ben)Apy) on cell proliferation and also on various events of HIV-1 replication cycle. The Topoisomerase II beta over-expressing neuroblastoma cell line shows a higher sensitivity to these compounds compared to the Sup-T1 cell line. All the three Topoisomerase 11 inhibitors show significant anti-HIV activity at nanomolar concentrations against an Indian isolate of HIV-1(93IN103) in Sup-T1 cell line. An analysis of action of these compounds on proviral DNA synthesis at 5 h of post-infection shows that they inhibit proviral DNA synthesis as well as the formation of pre-integration complexes completely. Further analysis, using polymerase chain reaction and western blot, showed that both the Topoisomerase 11 alpha and beta isoforms are present in the pre-integration complexes, suggesting their significant role in HIV-1 replication. (c) 2006 Elsevier Inc. All rights reserved.