The determination of a high resolution structure of the Trypanosoma brucei editosome

• Applicant: Professor Dr. H. Ulrich Göringer
• Subject Area: Structural Biology ; General Genetics and Functional Genome Biology ; Biochemistry ; Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437436849

Primary goal of this proposal is the determination of a high resolution structure of the editosome from the parasitic organism Trypanosoma brucei. Editosome are high molecular mass, multicomponent protein complexes that catalyze the essential U-nucleotide specific RNA editing reaction of the parasite. Importantly, trypanosomes are medically important organisms. The parasite is the causative agent of human African trypanosomiasis (HAT), also known as sleeping sickness. HAT is a neglected tropical disease for which novel therapeutics are urgently needed. However, the design of new drugs requires detailed knowledge of parasite-specific target structures to attack the infectious organism specifically. This puts the RNA editing machinery at the centre of attention. RNA editing is required for the survival of the parasite and U-insertion/deletion-type RNA editing does not exist in any of the host organisms of the parasite. As such the editosome represents a prime target for the development of novel intervention strategies. However, only a few inhibitors of the editing reaction have been identified today. This is in large parts due to the lack of structural knowledge. A structure-based search for low molecular mass inhibitors has so far not been possible since a high resolution structure of the editosome is missing. As a consequence we suggest to determine a high resolution structure of the T. brucei editosome using cryo-electron microscopy (cryo-EM). Furthermore, we aim at a full biophysical characterization of the editosome including its S-value, diffusion coefficient and particle dimensions. We will identify the pre-mRNA-substrate binding site(s) and the catalytic reaction centre of the complex and we will characterize the RNA-interaction surface of all substrate pre-mRNAs with the editosomal complex. Main motivation for the proposal are the recent improvements in cryo-EM. New generations of electron detectors record images with unprecedented quality and in combination with new image-processing algorithms generate density maps with near atomic detail. This makes it likely that the current low resolution structure of the editosome can be converted into a high resolution model. This should resolve some of the long standing questions in the field such as the stoichiometry of editosomal proteins, the structure of the dual-function (U-insertion/U-deletion) reaction centre and the pre-mRNA contact sites with the catalytic machinery. Moreover, we anticipate that the data will pave way to the rational design of RNA editing-specific inhibitors in order to contribute to the medical problem mentioned above.

• DFG Programme: Research Grants