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MGME1 processes flaps into ligatable nicks in concert with DNA polymerase γ during mtDNA replication

Lookup NU author(s): Dr Thomas NichollsORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Recently, MGME1 was identified as a mitochondrial DNA nuclease with preference for single-stranded DNA (ssDNA) substrates. Loss-of-function mutations in patients lead to mitochondrial disease with DNA depletion, deletions, duplications and rearrangements. Here, we assess the biochemical role of MGME1 in the processing of flap intermediates during mitochondrial DNA replication using reconstituted systems. We show that MGME1 can cleave flaps to enable efficient ligation of newly replicated DNA strands in combination with POLγ. MGME1 generates a pool of imprecisely cut products (short flaps, nicks and gaps) that are converted to ligatable nicks by POLγ through extension or excision of the 3'-end strand. This is dependent on the 3'-5' exonuclease activity of POLγ which limits strand displacement activity and enables POLγ to back up to the nick by 3'-5' degradation. We also demonstrate that POLγ-driven strand displacement is sufficient to generate DNA- but not RNA-flap substrates suitable for MGME1 cleavage and ligation during replication. Our findings have implications for RNA primer removal models, the 5'-end processing of nascent DNA at OriH, and DNA repair.

Publication metadata

Author(s): Uhler JP, Thörn C, Nicholls TJ, Matic S, Milenkovic D, Gustafsson CM, Falkenberg M

Publication type: Article

Publication status: Published

Journal: Nucleic Acids Research

Year: 2016

Volume: 44

Issue: 12

Pages: 5861-5871

Print publication date: 08/07/2016

Online publication date: 24/05/2016

Acceptance date: 13/05/2016

Date deposited: 27/02/2019

ISSN (print): 1362-4954

ISSN (electronic): 1362-4962

Publisher: Oxford University Press


DOI: 10.1093/nar/gkw468

PubMed id: 27220468


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