Analysis of Arabidopsis G-quadruplex sequence

Abstract

Guanine-rich DNA sequences often form G-quartets, planar arrays of four guanines stabilized by monovalent cations (K⁺ and Na⁺); which interact to form a G-quadruplex. In telomeres, G-rich sequences (repeats of TTTAGGG) form a G-quadruplex that interferes in the elongation reaction by telomerase. Recent bioinformatics analysis revealed that G-quadruplex-forming sequences exist ubiquitously in mammalian and bacterial genomes, and are enriched in promoters and near the translation start sites. Ligand binding of a G-quadruplex may decrease transcription of downstream genes. These findings support the current hypothesis that G-quadruplex may be a novel type of ubiquitous regulatory element. We studied the G-quadruplex sequence and its regulatory mechanism in Arabidopsis. Sequence analysis showed that the Arabidopsis genome possesses approximately 1,000 G-quadruplex sequences (approximately 700 genes). We also report that the similarity of G-quadruplex sequences and the changes of expression in genes nearest a G-quadruplex by the binding of its ligand.