Universität zu Köln

Niftullayev, Sadig (2024). Investigating the role of autophagy in mitochondrial and nuclear genome maintenance. PhD thesis, Universität zu Köln.

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Abstract

Autophagy is an evolutionarily conserved degradative mechanism. Being a central player in cellular stress responses, autophagy is activated by various stressors including nutritional stress. Autophagy has been reported to play an important role in maintaining the integrity of nuclear and mitochondrial genomes. Consistently, defects in autophagy lead to aberrations in the integrity of both nuclear and mitochondrial DNA. The mechanisms through which autophagy protects the cellular genomes, however, have largely been elusive. Previously, we have reported that, upon nitrogen starvation, yeast cells lacking autophagy suffer from nucleotide imbalance and elevated ROS levels, consequently degrading their mtDNA in a polymerase γ (POLG)-dependent fashion, a process we name POMD. Here, I report that, in parallel to the mtDNA degradation, autophagy-deficient cells also display signs of nuclear DNA damage such as H2AX phosphorylation, Rad51 and Rad52 foci formation, and elevated nuclear mutation rate. Remarkably, my data show that POMD is the main driver of DNA damage response observed in autophagy-deficient cells during starvation. Interestingly POMD-driven DDR requires yeast VDAC homolog Porin1 and the core components of the DNA repair machinery— the MRX complex, Tel1, and the key proteins of the homologous recombination pathway. Moreover, the plasmid-encoded heterologous expression of mouse cGAS also significantly attenuates the DDR in starved autophagy-deficient cells. Finally, I show that autophagy-deficient cells maintain lower steady-state levels of the homologous recombination pathway proteins compared to WT cells and fail to repair MMS-induced DNA damage. Together, my findings support a model in which autophagy-deficient cells induce a strong DNA damage response during starvation as a result of Por1-mediated release of POMDgenerated mtDNA fragments and compromised DNA repair machinery.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Niftullayev, Sadig sniftullayev@age.mpg.de UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-733204
Date:	2024
Place of Publication:	Cologne, Germany
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Biology of Ageing
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language autophagy English mtDNA English DNA damage English mtDNA release English nitrogen starvation English
Date of oral exam:	15 July 2024
Referee:	Name Academic Title Graef, Martin Dr. Rugarli, Elena Prof. Dr,
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/73320