Unravelling the role of SNM 1 in the DNA repair system of T rypanosoma brucei

• Published in: Molecular microbiology Vol. 96; no. 4; pp. 827 - 838
• Main Authors: Sullivan, James A., Tong, Jie Lun, Wong, Martin, Kumar, Ambika, Sarkar, Hajrah, Ali, Sarah, Hussein, Ikran, Zaman, Iqra, Meredith, Emma Louise, Helsby, Nuala A., Hu, Longqin, Wilkinson, Shane R.
• Format: Journal Article
• Language: English
• Published: 01.05.2015
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.12973

Summary All living cells are subject to agents that promote DNA damage. A particularly lethal lesion are interstrand cross‐links ( ICL ), a property exploited by several anti‐cancer chemotherapies. In yeast and humans, an enzyme that plays a key role in repairing such damage are the PSO 2/ SNM 1 nucleases. Here, we report that T rypanosoma brucei , the causative agent of A frican trypanosomiasis, possesses a bona fide member of this family (called TbSNM 1) with expression of the parasite enzyme able to suppress the sensitivity yeast pso2Δ mutants display towards mechlorethamine, an ICL ‐inducing compound. By disrupting the T b snm1 gene, we demonstrate that TbSNM 1 activity is non‐essential to the medically relevant T . brucei life cycle stage. However, trypanosomes lacking this enzyme are more susceptible to bi‐ and tri‐functional DNA alkylating agents with this phenotype readily complemented by ectopic expression of T b snm1 . Genetically modified variants of the null mutant line were subsequently used to establish the anti‐parasitic mechanism of action of nitrobenzylphosphoramide mustard and aziridinyl nitrobenzamide prodrugs, compounds previously shown to possess potent trypanocidal properties while exhibiting limited toxicity to mammalian cells. This established that these agents, following activation by a parasite specific type I nitroreductase, produce metabolites that promote formation of ICLs leading to inhibition of trypanosomal growth.