G4 formation in double-stranded DNA

Folding of G-quadruplex (G4) DNA structures within genomic DNA have emerged as important regulatory elements during replication, transcription or DNA repair. While many in-vitro studies have focused  on the kinetics of G4 formation within DNA single-strands, in-vivo G4 are found in double-stranded DNA regions like promoters, replication origins or telomeres, where their formation is challenged by pairing between the two complementary strands. Since, the energy of hybridization of Watson-Crick structures dominates the energy of G4 folding, this competition should play a critical role on the stability of G4 in vivo. To gain understanding in G4 formation within a double-strand context, we devised a single molecule automated assay. By repeating cycles of opening and closing of a DNA duplex using magnetic tweezers. (collaboration with Jean-Baptiste Boulé).