title: Two-quartet G-quadruplexes formed by DNA sequences containing four contiguous GG runs.
abstract: The DNA sequence containing four contiguous GG runs (G2NxG2NyG2NzG2, G2 sequence) has the potential to form a two-quartet G-quadruplex. However, the prevalence, structure, and function of G2 sequences have not been well-studied. Here, bioinformatics analysis reveals the abundance of G2 sequences in the human genome and their enrichment in promoter regions. The density of G2 sequences in the genome and promoters is much higher than that of the G3 sequence (G3NxG3NyG3NzG3). Experiments show that the conformations and thermal stabilities of the two-quartet G-quadruplexes of G2 sequences are highly sensitive to the length and composition of the loops. Among the two-quartet G-quadruplexes, the parallel G-quadruplex with a loop length of 1 and the antiparallel G-quadruplex with a loop length of 3 show high thermal stabilities. Additionally, the stable parallel G-quadruplexes are stacked into intermolecular higher-order structures. This work determines the prevalence of G2 sequences in the human genome and demonstrates that the G-quadruplex structures for certain loop lengths and compositions may be stable in vivo. Thus, more attention should be paid to the structure and function of the two-quartet G-quadruplex.
authors.affiliation: Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China.
authors.forename: Mingyan
authors.initials: M
authors.lastname: Qin
authors.forename: Zhuxi
authors.initials: Z
authors.lastname: Chen
authors.forename: Qichao
authors.initials: Q
authors.lastname: Luo
authors.forename: Yi
authors.initials: Y
authors.lastname: Wen
authors.forename: Naixia
authors.initials: N
authors.lastname: Zhang
authors.forename: Hualiang
authors.initials: H
authors.lastname: Jiang
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Yang
mesh_terms: D004247:DNA / Q000737:chemistry*; D054856:G-Quadruplexes; D015894:Genome, Human; D023281:Genomics; D006801:Humans; D013696:Temperature
chemical_list: D004247:DNA