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DNA polymerase gamma mutations that impair holoenzyme stability cause catalytic subunit depletion.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Silva-Pinheiro, Pedro  ORCID logo  https://orcid.org/0000-0002-0872-5749
Pardo-Hernández, Carlos  ORCID logo  https://orcid.org/0000-0001-6050-0566
Tilokani, Lisa 
Mishra, Anup 

Abstract

Mutations in POLG, encoding POLγA, the catalytic subunit of the mitochondrial DNA polymerase, cause a spectrum of disorders characterized by mtDNA instability. However, the molecular pathogenesis of POLG-related diseases is poorly understood and efficient treatments are missing. Here, we generate the PolgA449T/A449T mouse model, which reproduces the A467T change, the most common human recessive mutation of POLG. We show that the mouse A449T mutation impairs DNA binding and mtDNA synthesis activities of POLγ, leading to a stalling phenotype. Most importantly, the A449T mutation also strongly impairs interactions with POLγB, the accessory subunit of the POLγ holoenzyme. This allows the free POLγA to become a substrate for LONP1 protease degradation, leading to dramatically reduced levels of POLγA in A449T mouse tissues. Therefore, in addition to its role as a processivity factor, POLγB acts to stabilize POLγA and to prevent LONP1-dependent degradation. Notably, we validated this mechanism for other disease-associated mutations affecting the interaction between the two POLγ subunits. We suggest that targeting POLγA turnover can be exploited as a target for the development of future therapies.

Description

Keywords

ATP-Dependent Proteases, Animals, Cells, Cultured, DNA Polymerase gamma, DNA Replication, DNA, Mitochondrial, Enzyme Stability, HeLa Cells, Holoenzymes, Humans, Mice, Mitochondrial Proteins, Mutation

Journal Title

Nucleic Acids Res

Conference Name

Journal ISSN

0305-1048
1362-4962

Volume Title

49

Publisher

Oxford University Press (OUP)
Sponsorship
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (721757)
MRC (MC_UU_00015/4)
Medical Research Council (MC_UU_00015/4)
Medical Research Council (MC_UU_00015/7)
Medical Research Council (MC_UU_00015/8)
MRC (MC_UU_00015/8)