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The EM structure of human DNA polymerase gamma reveals a localized contact between the catalytic and accessory

Elena Yakubovskaya1, Mark Lukin, Zhixin Chen

  • 1Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA.

The EMBO Journal
|September 1, 2007
PubMed

Insights

Researchers visualized human DNA polymerase gamma (pol γ), crucial for mtDNA replication and linked to diseases. They mapped the accessory subunit (pol γB₂) interaction site on the catalytic subunit (pol γA), revealing structural insights into enzyme function and mutations.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Human DNA polymerase gamma (pol γ) is a heterotrimeric enzyme essential for mitochondrial DNA (mtDNA) replication.
  • Dysfunctional pol γ is implicated in various mitochondrial diseases and aging processes.
  • Understanding pol γ structure is key to elucidating its role in health and disease.

Purpose of the Study:

  • To determine the structural organization of the human pol γ holoenzyme.
  • To identify the precise location of the accessory subunit (pol γB₂) interaction with the catalytic subunit (pol γA).
  • To provide a structural basis for understanding disease-related mutations in pol γ.

Main Methods:

  • Electron microscopy was employed to visualize the structure of human pol γ.
  • Negative staining techniques were used for analyzing the catalytic subunit (pol γA) and the holoenzyme (pol γA/pol γB₂).

Main Results:

  • The position of the dimeric accessory factor (pol γB₂) within the holoenzyme was unambiguously identified.
  • A model was developed explaining the protection of a pol γA cleavage site (L549) upon pol γB₂ binding.
  • The interaction site was localized near pol γA residue 467, a known mutation site affecting pol γB subunit binding.
  • One pol γB subunit primarily contacts pol γA, while the second pol γB subunit is solvent-exposed.

Conclusions:

  • A structural model for human pol γ is proposed, detailing subunit interactions.
  • The findings offer insights into how mutations in the accessory subunit affect enzyme function.
  • The study enhances understanding of pol γ's interaction with DNA and its implications in disease.

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