Abstract 580: Cardiovascular Risks of Oxidative DNA Damage

Abstract

G-quadruplexes (or G4s) are nucleic-acid structures formed by guanine-rich sequences. G4s must be timely unfolded in cells; otherwise, they can interfere with DNA replication, RNA transcription, and other essential processes. Guanine bases are susceptible to forming 8-oxoguanine (8oxoG) as a result of oxidative damage. Although 8oxoG-modified DNA sequences can still fold into stable G4s, it is not known how 8oxoG4s are removed in human cells. We have shown previously that the FANCJ DNA helicase targets G4s using an AKKQ amino acid motif and unfolds them with its motor activity. Here, we have examined the interactions of FANCJ with various 8oxoG4s using biolayer interferometry and fluorescence spectroscopy. We show that a FANCJ AKKQ peptide alone can recognize G4s independently. Moreover, this motif binds to 8oxoG4s with greater affinities. A detailed description of the mechanisms by which 8oxoG4s are repaired is essential for understanding how human hearts respond to oxidative stress. To test the importance of FANCJ AKKQ-G4 interactions in cells, we measured the total extent of oxidative DNA damage in human cardiomyocytes by single-cell electrophoresis. Cells that overexpress FANCJ can readily overcome the chemical stress induced by hydrogen peroxide treatment and the G4-stabilizing compound telomestatin. On the contrary, cells that produce a FANCJ ADDQ mutant, which cannot interact with G4s, resulted in an accumulation of 8oxoG4s. Based on this evidence, FANCJ plays an important role to alleviate the damage caused by oxidative stress. In future experiments, we plan to further examine the cardiovascular risks of DNA damage caused by FANCJ malfunctions.