Abstract 500: Impact of Oxidative Stress and Fancj on Heart Health

Abstract

G-quadruplexes (or G4s) are structures formed by guanine-rich nucleic acid sequences. G4s must be promptly unfolded in cells; otherwise, they can interfere with DNA replication, RNA transcription, and other essential processes. Guanines bases are susceptible to oxidative stress forming 8-oxoguanines (8oxoG). Although 8oxoG-modified DNA sequences can still fold into stable G4s, it is not known how 8oxoG4s are repaired in human cells. In our previous study, we have shown that the FANCJ DNA helicase targets G4s using an AKKQ amino acid motif. 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 with an affinity of 3.7uM. Moreover, this motif binds to 8oxoG4s with greater affinities of 1.3 to 2.3uM. 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 cardiac cells 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 AAAQ 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.