Molecular analysis of the human smc5/6 complex and the nse1 ring domain in genome integrity
- Autores: Neus Perez Lorite
- Directores de la Tesis: Jordi Torres-Rosell (dir. tes.), Neus Colomina Gabarrella (dir. tes.)
- Lectura: En la Universitat de Lleida ( España ) en 2024
- Idioma: español
- Tribunal Calificador de la Tesis: Belén Gómez González (presid.), Águeda Martínez Barriocanal (secret.), Emilio Lecona Sagrado (voc.)
- Programa de doctorado: Programa de Doctorado en Salud por la Universidad de Lleida
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Maintaining genome stability during chromosome replication and segregation is crucial for cellular homeostasis and preventing tumorigenesis. Structural maintenance of chromosomes (SMC) protein complexes are key players in this process, ensuring proper genome organisation, compaction, and repair. Specifically, the multi-subunit SMC5/6 complex safeguards genome stability by enabling the completion of DNA replication, although the precise ways in which it operates at replication forks remains unknown.
Within the SMC5/6 complex, the NSE1 subunit has a RING domain, characteristic of E3 ubiquitin ligases. However, the actual role of this domain remains to be fully elucidated. Here we show that the NSE1 RING domain is essential for the stability of the SMC5/6 complex, as point mutations or truncations in the RING domain drastically reduce SMC5/6 protein levels, with differential contribution of the two zinc-coordinating centers. HEK293T nse1 mutant cells, as well as HCT116 cells depleted of the SMC5/6 complex, display increased genomic instability and slower replication forks. In addition, and differently to other organisms, our results indicate that human SMC5/6 controls fork progression and chromosome disjunction independently of FANCM, leading to a synthetic sick interaction between SMC5/6 and FANCM. Conversely, SMC5/6 slows replication by promoting fork reversal during replicative stress, pointing to a new role in the remodelling of stalled forks. Finally, we show that SMC5/6 is epistatic to different fork remodelers in the control of fork speed and fork reversal during replicative stress. These results place the SMC5/6 complex as a new player in the protection of stalled forks, most probably by controlling the topology of nascent strands.
Overall, our research demonstrates that the NSE1 RING domain plays vital roles in SMC5/6 complex stability and fork progression. Furthermore, our findings indicate that the SMC5/6 complex collaborates with fork remodelers to control fork progression and stability, protecting against the detrimental effects of replicative stress and promoting genome integrity.
