Quadruplexes and the Biology of G-Rich Genomic Regions

Departments of Immunology and Biochemistry, University of Washington Medical School, Seattle, WA, USA 

When we picture DNA, the image that comes immediately to mind is the iconic double helix. However, the double helix is only the storage form for genetic information, and DNA takes on very different structures when actively used during transcription, replication, and recombination. G-rich genomic regions have unusual structural potential, as they readily form G-quadruplex structures. This chapter discusses how regulated formation of G-quadruplexes contributes to key cellular processes. 

1 G-Rich Nucleic Acids Spontaneously Form G4 DNA or G4 RNA in Vitro 

Formation of G-quadruplex structures occurs spontaneously in synthetic DNAs which contain at least four runs of guanines, each at least 3 nt in length (GGG). A minimalist example is (TTAGGG)4, a 4-mer repeat of the vertebrate telomeric sequence, which readily forms G4 DNA. Some sequences containing shorter G-runs will form G-quadruplexes, although this may depend upon the number and identity of bases in the loops between the G-planes, and the 

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