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Intracellular transcription of G-rich DNAs induces formation of G-loops, novel structures containing G4 DNA

2004; Cold Spring Harbor Laboratory Press; Volume: 18; Issue: 13 Linguagem: Inglês

10.1101/gad.1200804

1549-5477

Michelle L. Duquette, Priya Handa, Jack A Vincent, Andrew F. Taylor, Nancy Maizels,

Genomics and Chromatin Dynamics

We show that intracellular transcription of G-rich regions produces novel DNA structures, visible by electron microscopy as large (150–500 bp) loops. These G-loops are formed cotranscriptionally, and they contain G4 DNA on one strand and a stable RNA/DNA hybrid on the other. G-loop formation requires a G-rich nontemplate strand and reflects the unusual stability of the rG/dC base pair. G-loops and G4 DNA form efficiently within plasmid genomes transcribed in vitro or in Escherichia coli . These results establish that G4 DNA can form in vivo, a finding with implications for stability and maintenance of all G-rich genomic regions.