Work

Formation of the G-quadruplex and i-motif structures in retinoblastoma susceptibility genes (Rb)

Year: 2006

Type: article

Abstract: The formation of G-quadruplex and i-motif structures in the 5' end of the retinoblastoma (Rb) gene was examined using chemical modifications, circular dichroism (CD) and fluorescence spectroscopy. It was found that substitutions of 8-methylguanine at positions that show syn conformations in antiparallel G-quadruplexes stabilize the structure in the G-rich strand. The complementary C-rich 18mer forms an i-motif structure, as suggested by CD spectroscopy. Based on the C to T mutation experiments, C bases participated in the C-C+ base pair of the i-motif structure were determined. Experiments of 2-aminopurine (2-AP) substitution reveal that an increase of fluorescence in the G-quadruplex relative to duplex is attributed to unstacked 2-AP within the loop of G-quadruplex. The fluorescence experiments suggest that formation of the G-quadruplex and i-motif can compete with duplex formation. Furthermore, a polymerase arrest assay indicated that formation the G-quadruplex structure in the Rb gene acts as a barrier in DNA synthesis.

Source: Nucleic Acids Research

DOI: 10.1093/nar/gkj485

Authors: Y. Xu, Hiroshi Sugiyama

Institution: Kyoto University

Language: English

Topic: DNA and Nucleic Acid Chemistry

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: gold

Estimated APC paid: $3,992

Funder: University of Oxford