In vitro tRNA methylation assay with the Entamoeba histolytica DNA and tRNA methyltransferase Dnmt2 (Ehmeth) enzyme.

Protozoan parasites are among the most devastating infectious agents of humans responsible for a variety of diseases including amebiasis, which is one of the three most common causes of death from parasitic disease. The agent of amebiasis is the amoeba parasite Entamoeba histolytica that exists under two stages: the infective cyst found in food or water and the invasive trophozoite living in the intestine. The clinical manifestations of amebiasis range from being asymptomatic to colitis, dysentery or liver abscesses. E. histolytica is one of the rare unicellular parasite with 5-methylcytosine (5mC) in its genome. It contains a single DNA methyltransferase, Ehmeth, that belongs to the Dnmt2 family. A role for Dnmt2 in the control of repetitive elements has been established in E. histolytica, Dictyostelium discoideum and Drosophila. Our recent work has shown that Ehmeth methylates tRNA(Asp), and this finding indicates that this enzyme has a dual DNA/tRNA(Asp) methyltransferase activity. This observation is in agreement with the dual activity that has been reported for D. discoideum and D. melanogaster. The functional significance of the DNA/tRNA specificity of Dnmt2 enzymes is still unknown. To address this question, a method to determine the tRNA methyltransferase activity of Dnmt2 proteins was established. In this video, we describe a straightforward approach to prepare an adequate tRNA substrate for Dnmt2 and a method to measure its tRNA methyltransferase activity.