Estudio de las funciones de TRIP13 en la profase meiótica de mamíferos

Abstract

At the onset of meiotic prophase, SPO11 produces double-stranded breaks (DSBs), and its repair by homologous recombination (HR) promotes homologous chromosomes to pair and synapse. During meiosis, repairing DSBs by HR or non-homologous end joining (NHEJ) requires very strict regulation. Synaptonemal complex (SC) proteins are recruited into chromosome axes, which is essential for meiotic recombination to be completed. TRIP13, also known as Pch2 in nonvertebrate species, belongs to the AAA+ ATPases family of proteins. Some of TRIP13's functions are explained by its ability to change the conformation of proteins that possess the HORMA domain, such as MAD2, HORMAD1 and REV7. TRIP13 is located in the synapsed portions of SC and at the telomeres, a location not described yet in any other model organism. To learn more about TRIP13 functions in DSBs repair and homologous chromosome synapsis, we have used several Trip13 mutants, like Trip13mod/mod, Trip13sev/sev, we generated Trip13-/- and Trip13ATPaseDead murine mutants and we have also performed pharmacological treatment using a TRIP13 inhibitor. TRIP13 and its interacting proteins were also immunoprecipitated from testis protein extracts and identified by mass spectrometry. The results of mass spectrometry revealed that the HSPA2 chaperone, a factor that controls desynapsis, is a TRIP13 interactor. HSPA2 and PLK1, another protein that promotes desynapsis, are dysregulated in Trip13 mutants. Trip13 mutant spermatocytes exhibit defects in synapsis and accumulate unrepaired DSBs. In this work we propose that TRIP13 avoids premature SC desynapsis during meiotic prophase, regulating the presence of desynaptic factors. On the other hand, in somatic cells, TRIP13 regulates the choice of DSBs repair pathway by disassembling the Shieldin complex, in which REV7 takes part in the complex. Shieldin complex protects DSBs from resection, inhibiting their repair by HR and promoting it by NHEJ. In spermatocytes, we have observed that in the absence of TRIP13, HR markers are reduced and NHEJ markers are increased. In addition, Trip13 deficient spermatocytes have more fused chromosomes by the telomeres, a 53BP1-dependent effect.

Date of Award	10 Feb 2023
Original language	Spanish
Supervisor	Ignasi Roig Navarro (Director)