The formation of G-quadruplex structure in genome has to compete with the double helix structure in the presence of a complementary strand and constraint at both ends with long DNA duplex. Whether G-quadruplex can form or under what circumstances it forms is a question that has to be addressed. Using DMS footprinting and gel electrophoresis, TAN Zheng's team observed G-quadruplex formation in the process of RNA transcription in long double-stranded DNA derived from human genome. They found that molecular crowding condition with PEG at concentrations near the physiological concentration of biomass in living cells facilitate G-quadruplex formation. This observation reveals the physical basis for the formation of stable G-quadruplexes in double stranded DNA and supports its presence in vivo.

Refer to: Zheng KW, Chen Z, Hao YH, Tan Z. 2010. Molecular crowding creates an essential environment for the formation of stable G-quadruplexes in long double-stranded DNA. Nucleic Acids Res 38(1): 327-338.

FUNDING: Grants from MSTC; and NSFC. Funding for open access charge: MSTC.