Caracterización estructural y funcional del complejo THO de Saccaromyces Cerevisiae

Résumé

In eukaryotic cells the genetic information is protected and stored in the nucleus. In order to perform its function, genetic material has to be copied to a temporal ribonucleotide molecule termed messenger RNA (mRNA). The mRNA traverses the nuclear envelope carrying the genetic information to ribosomes, the sites of protein synthesis in the cytoplasm. mRNA¿s export requires the recruitment of export factors into the mRNA, forming the ribonucleoprotein complexes or mRNPs. This thesis is focused on the structural characterization of the Saccharomyces cerevisiae THO complex, which is directly implicated in the mRNP biogenesis. THO, a four-protein complex (Tho2, Hpr1, Mft1 y Thp2), assists the interaction between the export factors and the mRNA, and facilitates the genetic information flow from the nucleus to the cytoplasm. The THO complex expedites gene expression and at the same time contributes to the cell genetic-stability and collaborates with the quality control mechanisms that ensure the production of active mRNA molecules. This work has served to generate for the first time a three-dimensional reconstruction of THO complex. Furthermore, it has been indentified the interaction between the THO complex and the Tex1 protein, which interacts with the complex in vivo during the transcription process. Moreover, the localization inside the complex of one of the most important THO¿s components, Hpr1, has been determined. Finally, the specific region of THO complex involved in the interaction with nucleic acids, has been identified and its importance for the cellular survival has been tested. Bringing together these results, it has been suggested a new action-model for the initial steps of the genetic expression in S. cerevisiae, that contributes to the understanding of this process in agreement with the current knowledge.