A cluster of pathogenic mutations in the 3'-5' exonuclease domain of DNA polymerase gamma defines a novel module coupling DNA synthesis and degradation.

Karolina Szczepanowska, Françoise Foury

Institute of Life Sciences, Croix du Sud 4/15, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.

Human molecular genetics 2010 Sep 15

filter terms:

Mutations in DNA polymerase gamma (pol g), the unique replicase inside mitochondria, cause a broad and complex spectrum of diseases in human. We have used Mip1, the yeast pol g, as a model enzyme to characterize six pathogenic pol g mutations. Four mutations clustered in a highly conserved 3'-5' exonuclease module are localized in the DNA-binding channel in close vicinity to the polymerase domain. They result in an increased frequency of point mutations and high instability of the mitochondrial DNA (mtDNA) in yeast cells, and unexpectedly for mutator mutations in the exonuclease domain, they favour exonucleolysis versus polymerization. This trait is associated with highly decreased DNA-binding affinity and poorly processive DNA synthesis. Our data show for the first time that a 3'-5' exonuclease module of pol g plays a crucial role in the coordination of the polymerase and exonuclease functions and they strongly suggest that in patients the disease is not caused by defective proofreading but results from poor mtDNA replication generated by a severe imbalance between DNA synthesis and degradation.

Citation

Karolina Szczepanowska, Françoise Foury. A cluster of pathogenic mutations in the 3'-5' exonuclease domain of DNA polymerase gamma defines a novel module coupling DNA synthesis and degradation. Human molecular genetics. 2010 Sep 15;19(18):3516-29