Análisis estructura-función de la ATPasa Pch2 y su implicación en el Checkpoint de recombinación meiótica

Resumen

During meiosis there is a surveillance mechanism, the meiotic recombination checkpoint, which monitors the correct distribution of genetic material to gametes, being crucial for the maintenance of genomic integrity in sexually reproducing organisms. We aimed to further explore the role of Pch2, a meiosis-specific AAA+ ATPase, in the meiotic recombination checkpoint of Saccharomyces cerevisiae. In this thesis, we have determined that the critical role of Pch2 in the checkpoint induced by synapsis defects is to promote Hop1 phosphorylation at T318 and Hop1 association to unsynapsed meiotic chromosomes. We have also studied the functional relevance of critical residues of the Pch2 protein, such as the catalytic site (ATPase activity) and the N-terminal domain, by analyzing its impact on Pch2 localization and checkpoint function. On the other hand, we have contributed to discover several factors that determine Pch2 proper localization in yeast. Thus, we have revealed that, together with H3K79 methylation, proper levels of H4K16 acetylation regulate the meiotic recombination checkpoint, likely by controlling Pch2 distribution. Moreover, we have analyzed Orc1-Pch2 interaction at the ribosomal DNA (rDNA), concluding that, in contrast to previous hypotheses, Pch2 nucleolar localization is not required for the meiotic checkpoint. Indeed, we provide evidence indicating that a cytoplasmic pool of Pch2 sustains checkpoint function. Finally, we have expanded our investigation to another model system such as Caenorhabditis elegans. We have studied the meiotic role of H3K79 methylation in this nematode, analyzing its checkpoint implication and exploring its impact on PCH-2 regulation. In conclusion, the evolutionarily conserved Pch2 ATPase plays a critical role in the meiotic checkpoint induced by synapsis defects. The control of Pch2 subcellular localization orchestrated by several factors, including histone post-translational modifications, is vital for its checkpoint function.