AUTHOR=Park Joon , Baruch-Torres Noe , Iwai Shigenori , Herrmann Geoffrey K. , Brieba Luis G. , Yin Y. Whitney 

TITLE=Human Mitochondrial DNA Polymerase Metal Dependent UV Lesion Bypassing Ability

JOURNAL=Frontiers in Molecular Biosciences

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2022.808036

DOI=10.3389/fmolb.2022.808036

ISSN=2296-889X

ABSTRACT=<p>Human mitochondrial DNA contains more UV-induced lesions than the nuclear DNA due to lack of mechanism to remove bulky photoproducts. Human DNA polymerase gamma (Pol γ) is the sole DNA replicase in mitochondria, which contains a polymerase (<italic>pol</italic>) and an exonuclease (<italic>exo</italic>) active site. Previous studies showed that Pol γ only displays UV lesion bypassing when its exonuclease activity is obliterated. To investigate the reaction environment on Pol γ translesion activity, we tested Pol γ DNA activity in the presence of different metal ions. While Pol γ is unable to replicate through UV lesions on DNA templates in the presence of Mg<sup>2+</sup>, it exhibits robust translesion DNA synthesis (TLS) on cyclobutane pyrimidine dimer (CPD)-containing template when Mg<sup>2+</sup> was mixed with or completely replaced by Mn<sup>2+</sup>. Under these conditions, the efficiency of Pol γ′s TLS opposite CPD is near to that on a non-damaged template and is 800-fold higher than that of exonuclease-deficient Pol γ. Interestingly, Pol γ exhibits higher exonuclease activity in the presence of Mn<sup>2+</sup> than with Mg<sup>2+</sup>, suggesting Mn<sup>2+</sup>-stimulated Pol γ TLS is not via suppressing its exonuclease activity. We suggest that Mn<sup>2+</sup> ion expands Pol γ′s <italic>pol</italic> active site relative to Mg<sup>2+</sup> so that a UV lesion can be accommodated and blocks the communication between <italic>pol</italic> and <italic>exo</italic> active sites to execute translesion DNA synthesis.</p>