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MITOL-dependent ubiquitylation negatively regulates the entry of PolγA into mitochondria

Mansoor Hussain1, Aftab Mohammed1, Shabnam Saifi1

  • 1National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.

Plos Biology
|March 3, 2021
PubMed

Insights

Mitochondrial polymerase PolγA entry into mitochondria is regulated by ubiquitylation, a process crucial for mitochondrial DNA replication and preventing progressive external ophthalmoplegia (PEO). Modulating this ubiquitylation can restore function in PEO patients.

Area of Science:

  • Mitochondrial biology
  • Molecular genetics
  • Cellular regulation

Background:

  • Mutations in mitochondrial replicative polymerase PolγA are linked to progressive external ophthalmoplegia (PEO).
  • The mechanism controlling PolγA entry into mitochondria remains unclear.
  • Mitochondrial DNA (mtDNA) replication is essential for cellular energy production.

Purpose of the Study:

  • To investigate the regulation of PolγA entry into mitochondria.
  • To determine the role of ubiquitylation in PolγA function and PEO pathogenesis.
  • To explore therapeutic strategies for PEO by targeting PolγA regulation.

Main Methods:

  • Immunoprecipitation and Western blotting to detect ubiquitylation of PolγA.
  • Analysis of PolγA binding to Tom20, a mitochondrial import receptor.
  • Assessment of mtDNA replication using BrdU incorporation assays.
  • Genetic manipulation to alter PolγA ubiquitylation status.

Main Results:

  • PolγA is ubiquitylated by MITOL (MARCH5, RNF153) at Lysine 1060 via K6 linkage.
  • Ubiquitylation negatively regulates PolγA binding to Tom20, inhibiting mitochondrial import.
  • Certain PEO-associated PolγA mutants are hyperubiquitylated, leading to impaired mitochondrial entry and mtDNA replication.
  • Reactivation of these mutants by manipulating ubiquitylation restored mtDNA replication.

Conclusions:

  • Regulated entry of non-ubiquitylated PolγA into mitochondria is critical for mtDNA replication.
  • Aberrant ubiquitylation of PolγA contributes to PEO pathogenesis.
  • Targeting PolγA ubiquitylation offers a potential therapeutic approach for PEO patients.

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