Cambridge researchers utilize markers to visualize G-quadruplexes in living cells

Cambridge University researchers used a special fluorescent marker to note the location of certain positions of DNA and RNA and found the positions fluctuate between two states, according to a recently released article.

The article, "Single-molecule visualization of DNA G-quadruplex formation in live cells," published in Nature on July 20, says G-quadruplexes fluctuate between two states, folded and unfolded.

"Substantial evidence now exists to support that formation of DNA G-quadruplexes is coupled to altered gene expression," the article's abstract said. "However, approaches that allow us to probe G4s in living cells without perturbing their folding dynamics are required to understand their biological roles in greater detail."

G-quadruplex-specific fluorescent probe, SiR-PyPDS, "enables single-molecule and real-time detection" of G-quadruplex structures in living cells, the abstract said. "Live-cell single-molecule fluorescence imaging of G4s was carried out under conditions that use low concentrations of SiR-PyPDS [20 nM] to provide informative measurements representative of the population of G4s in living cells, without globally perturbing G4 formation and dynamics. Single-molecule fluorescence imaging and time-dependent chemical trapping of unfolded G4s in living cells reveal that G4s fluctuate between folded and unfolded states."

The article also argues that the formation "is cell-cycle-dependent and disrupted by chemical inhibition of transcription and replication, noting, "Our observations provide robust evidence in support of dynamic G4 formation in living cells."

The articles authors are Marco Di Antonio, Aleks Ponjavic, Rohan T. Ranasinghe, Marco Catalano, Xiaoyun Zhang, Lisa-Maria Needham, Steven F. Lee, David Klenerman, Shankar Balasubramanian and Antanas Radzevičius with the Department of Chemistry at Cambridge University, the Chemistry Department at Imperial College London and the Molecular Science Research Hub in London. Jiazhen Shen, a cancer researcher at Cambridge University, also contributed.

Klenerman and Balasubramanian, known for their work in DNA sequencing, are contact leads on the article.

G-quadruplexes are positions in a DNA molecule in which four guanines, one of the four main nucleobases in DNA and RNA, join to form a four-stranded molecule. G-quadruplexes influence how genes are expressed and are considered a type of epigenetic marker.