Expert Opinion on Drug Discovery

Background: Members of the nucleotidyltransferase superfamily known as DNA and RNA ligases carry out the enzymatic process of polynucleotide ligation. These guardians of genomic integrity share a three-step ligation mechanism, as well as common core structural elements. Both DNA and RNA ligases have experienced a surge of recent interest as chemotherapeutic targets for the treatment of a range of diseases, including bacterial infection, cancer and the diseases caused by the protozoan parasites known as trypanosomes. Objective: In this review, we will focus on efforts targeting pathogenic microorganisms; specifically, bacterial NAD⁺-dependent DNA ligases, which are promising broad-spectrum antibiotic targets, and ATP-dependent RNA-editing ligases from Trypanosoma brucei, the species responsible for the devastating neurodegenerative disease, African sleeping sickness. Conclusion: High-quality crystal structures of both NAD⁺-dependent DNA ligase and the T. brucei RNA-editing ligase have facilitated the development of a number of promising leads. For both targets, further progress will require surmounting permeability issues and improving selectivity and affinity.