Identification of non-telomeric G4-DNA binding proteins in human, E. coli, yeast, and Arabidopsis

G4-DNA binding proteins of E. coli, Saccharomyces cerevisiae, Arabidopsis, and human have been identified by a synthetic non-telomeric G4-DNA oligo 5'-d(ACTGTCGTACTTGATATGGGGGT)-3' using gel mobility shift assays. G4-DNA binding proteins are specific to G4-DNA, a four-stranded guanine-DNA structure. Bound complexes of G4-DNA and proteins were identified in nuclear extracts of all examined organisms in this study. In humans, three different G4-DNA and protein complexes were identified. However, human telomeric G-quadruplex oligo did not compete with G4-DNA oligo in the competition assays, suggesting that the identified G4-DNA binding proteins may be different from the known human telomeric G4-DNA binding proteins. We discovered two complexes of G4-DNA and protein in Arabidopsis identified in mobility shift assays. Interestingly, two complexes of G4-DNA and proteins were identified from E. coli, which have a circular genomic DNA structure. Results of this investigation suggest that non-telomeric G4-DNA structure and its binding proteins may be involved in important functional roles in both prokaryotes and eukaryotes.