Evolution of RNA modifying enzymes in Archaea
Epitranscriptomic; Archaea; RNA modifying enzymes; NAD-capping
RNA-modifying enzymes are biological catalysts that perform covalent modifications on RNA. These modifications are essential for many cellular processes, including the stabilization and formation of secondary structures in tRNAs and mRNAs, splicing and capping of mRNAs, protein translation, involvement in metabolic diseases, and gene expression control. These enzymes are present in all three domains of life (Bacteria, Archaea, and Eukarya); however, their evolutionary histories are poorly understood. Eukaryotes are derived from the fusion of Archaea and Bacteria, and recently, a group of prokaryotic organisms known as Asgard archaea has been identified as the closest living relatives of Eukarya, providing new insights into how eukaryotic evolution may have occurred. This work aims to bridge the evolutionary history of RNA-modifying enzymes with the phylogenetic relationship between Archaea and Eukarya. As an example of the interaction of these evolutionary histories, recent investigations into Archaea have explored NAD-capping RNA-modifying enzymes, which were previously described in bacteria and eukaryotes. For this study, protein sequences from a database called Modomics were analyzed. The analysis revealed that RNA-modifying enzymes and associated information in Archaea are scarce. Among the enzymes available in Modomics, we chose to characterize NAD-capping proteins belonging to the NUDIX superfamily. Among the studied proteins are the NudE proteins from Archaea, responsible for RNA decapping, which, as previously described, exhibit a new function in extreme environments. These proteins were found to perform RNA decapping with ADPR, an NAD analog easily degraded in extreme environments. The data obtained in this project suggest that the change in function may have occurred through molecular exaptation, i.e., the co-option of a pre-existing function for a new purpose. To better understand this process, tools were employed to characterize the domain architecture present in the proteins and to analyze structural groupings and overlap for both NudE and other NUDIX proteins. It was observed that these proteins have similar domain compositions and high structural similarity, indicating potential similar functions or molecular exaptation. However, phylogenetic and molecular docking studies need to be conducted to better understand this scenario.