CONICET | Buscador de Institutos y Recursos Humanos

Previously, we have shown that TbRRM1 is an essential protein in procyclic (PCF) and bloodstream form stages of T. brucei. We have also observed in PCF that its silencing by RNAi produced an increase in heterochromatin content and affected transcription of RNA Pol II genes suggesting that it would have a transcriptional role. Since TbRRM1 is absent in mammals and essential for parasite survival, but the crystallographic structure of TbRRM1 is not available, we built a 3D model of the RNA Recognition Motif (RRM), which is potentially a structure capable of being inhibited by drugs. The human UP1 protein was used as a template due to its significant sequence similarity to the T. brucei RRM. Models were built for each RRM, using the Full Model Builder tool in ICM Pro (La Jolla, CA, USA), which optimizes alignment between the UP1 structure and the RRM to preserve secondary structure. Electrostatic surfaces of RRMs were constructed to assess the charged RNA binding surface and identify possible ligand binding pockets. Surprisingly, the first RRM showed a negative overall charge, not expected for an RRM, while the second and third motifs showed positive surfaces around the binding region. This result indicates that the first RRM would have an alternative (non-canonical) role, and the binding of TbRRM1 protein to RNA occurs in the second and/or third RRM. Preliminary experimental evidence from the overexpression of a truncated version of TbRRM1 protein lacking the first RRM showed that parasite growth is partially affected after 72 hs of TET addition in contrast to the deleterious effects seen after the wild type TbRRM1 overexpression. These findings provide new perspectives on the biological role of TbRRM1 and contribute to understanding its role in the biology of the parasite.This project was partially funded by National University of La Matanza (UNLaM) through the Research Grants Vincular 2020 and PROINCE 2020-2021 to GVL.