DNA and Chromosomes
A biochemical and biophysical model of G-quadruplex DNA recognition by positive coactivator of transcription 4
DNA sequences that are guanine-rich have received considerable attention because of their potential to fold into a secondary, four-stranded DNA structure termed G-quadruplex (G4), which has been implicated in genomic instability and some human diseases. We have previously identified positive coactivator of transcription (PC4), a single-stranded DNA (ssDNA)-binding protein, as a novel G4 interactor. Here, to expand on these previous observations, we biochemically and biophysically characterized the interaction between PC4 and G4DNA.Evidence That G-quadruplex DNA Accumulates in the Cytoplasm and Participates in Stress Granule Assembly in Response to Oxidative Stress
Cells engage numerous signaling pathways in response to oxidative stress that together repair macromolecular damage or direct the cell toward apoptosis. As a result of DNA damage, mitochondrial DNA or nuclear DNA has been shown to enter the cytoplasm where it binds to “DNA sensors,” which in turn initiate signaling cascades. Here we report data that support a novel signaling pathway in response to oxidative stress mediated by specific guanine-rich sequences that can fold into G-quadruplex DNA (G4DNA).A Parallel Quadruplex DNA Is Bound Tightly but Unfolded Slowly by Pif1 Helicase
Background: Some G-rich sequences fold into intramolecular quadruplex structures. Pif1 helicase reduces genomic instability by unfolding quadruplex DNA.Results: Pif1 unfolds a parallel quadruplex structure slowly relative to unwinding of duplex DNA.Conclusion: Comparison of duplex unwinding to quadruplex unfolding is complicated by distinct kinetic mechanisms.Significance: A highly stable, intramolecular quadruplex is a formidable obstacle but can be overcome by Pif1 helicase.
