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Structural basis for processivity and antiviral drug toxicity in human mitochondrial DNA replicase
Author(s) -
Szymanski Michal R,
Kuznetsov Vladmir B,
Shumate Christie,
Meng Qingchao,
Lee YoungSam,
Patel Gayatri,
Patel Smita,
Yin Y Whitney
Publication year - 2015
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.15252/embj.201591520
Subject(s) - processivity , biology , dna polymerase , polymerase , primer (cosmetics) , protein subunit , microbiology and biotechnology , dna replication , biochemistry , dna , chemistry , organic chemistry , gene
The human DNA polymerase gamma (Pol γ) is responsible for DNA replication in mitochondria. Pol γ is particularly susceptible to inhibition by dideoxynucleoside‐based inhibitors designed to fight viral infection. Here, we report crystal structures of the replicating Pol γ– DNA complex bound to either substrate or zalcitabine, an inhibitor used for HIV reverse transcriptase. The structures reveal that zalcitabine binds to the Pol γ active site almost identically to the substrate dCTP , providing a structural basis for Pol γ‐mediated drug toxicity. When compared to the apo form, Pol γ undergoes intra‐ and inter‐subunit conformational changes upon formation of the ternary complex with primer/template DNA and substrate. We also find that the accessory subunit Pol γB, which lacks intrinsic enzymatic activity and does not contact the primer/template DNA directly, serves as an allosteric regulator of holoenzyme activities. The structures presented here suggest a mechanism for processivity of the holoenzyme and provide a model for understanding the deleterious effects of Pol γ mutations in human disease. Crystal structures of the mitochondrial DNA polymerase, Pol γ, in complex with substrate or antiviral inhibitor zalcitabine provide a basis for understanding Pol γ‐mediated drug toxicity.