Potent Antiviral Activity of Topoisomerase I and II Inhibitors against Kaposi's Sarcoma-Associated Herpesvirus

Abstract

. To assess the importance of these topoisomerases in viral lytic replication, shRNA-mediated gene silencing was used. Depletion of Topo I and II severely inhibited viral lytic DNA replication as well as virion production, suggesting essential roles of these cellular proteins in viral DNA replication. The discovery of Topo I and II as enzymes indispensable for KSHV DNA replication raises a possibility that these cellular proteins could be new targets of therapeutic approaches to halt KSHV replication and treat KSHV-associated diseases. In this report, we examined one Topo I inhibitor and several Topo II inhibitors (inclusive of Topo II poison and catalytic inhibitors) as potential therapeutic agents for blocking KSHV replication. The Topo II catalytic inhibitors in general exhibited marked inhibition on KSHV replication and minimal cytotoxicity. In particular, novobiocin, with the best selectivity index (SI ‫؍‬ 31.62) among the inhibitors tested in this study, is effective in inhibiting KSHV DNA replication and virion production but shows little adverse effect on cell proliferation and cycle progression in its therapeutic concentration, suggesting its potential to become an effective and safe drug for the treatment of human diseases associated with KSHV infection.

Kaposi's Sarcoma-Associated Herpesvirus-Encoded LANA Recruits Topoisomerase IIβ for Latent DNA Replication of the Terminal Repeats

“…KSHV and the other herpesviruses studied so far do not encode topoisomerases. Thus, it could be assumed that these viruses use cellular topoisomerases for the viral DNA replication (19,67). Indeed, the importance of TopoII␤ in KSHV lytic DNA replication was recently demonstrated (67).…”

“…It has been shown that gene silencing of TopoI and TopoII with specific short hairpin RNA (shRNA) or use of ellipticine, a specific inhibitor of TopoII, could abolish KSHV lytic DNA replication (19). Additionally, it has been shown that a wide variety of potential topoisomerase inhibitors effectively block KSHV lytic DNA replication and could be further screened as therapeutic drugs (19).…”

“…Since LANA has no detectable polymerase or helicase activity required for DNA replication, this strongly suggests that replication of the KSHV genome is dependent on enzymes that contain these activities and core components of the cellular replication machinery (42). Association of topoisomerase II (TopoII␤) with the KSHV TR region was identified by DNA affinity chromatography and proteomics analysis using KSHV TR DNA or ori-Lyt DNA as an affinity ligand and was furthermore demonstrated to be essential for KSHV lytic DNA replication (19,53,67).…”

Antiviral Activity of (+)-Rutamarin against Kaposi's Sarcoma-Associated Herpesvirus by Inhibition of the Catalytic Activity of Human Topoisomerase II

“…The final DMSO concentration in the culture medium was maintained at 1%. For lytic replication, BCBL-1 cells were induced by tetradecanoylphorbol acetate (TPA) as previously reported (20). JSC-1 cells were induced by 3 mM sodium butyrate (22).…”

“…We also demonstrated that both Topo I and Topo II are indispensable for KSHV lytic replication and that specific inhibitors of Topo I and II can effectively inhibit KSHV lytic replication. One category of Topo II inhibitors, namely, catalytic Topo II inhibitor, was found to provide marked inhibition of KSHV replication with minimal cytotoxicity, as indicated by their high selectivity indices (e.g., 31.6 for novobiocin) (20). As such, Topo II can serve as an effective target for antivirals, and catalytic inhibitors of Topo II represent promising antiviral agents for the treatment of malignancies associated with KSHV infection.…”