Decades-old DNA mystery solved after strands are captured zipping together for the first time

Scientists have finally captured the first-ever visual evidence of two DNA molecules binding together, after decades of puzzling over how this process occurs. Researchers at the University of Sheffield and the University of York used high-powered atomic force microscopy to observe the alignment of DNA strands groove-to-groove, a phenomenon that has confounded scientists for over two decades.

This breakthrough unveils a crucial mechanism at work in genetic recombination, gene silencing, chromosome packaging, and even cancer development.

The key to this DNA pairing lies in the interplay of negatively charged DNA molecules and positively charged metal ions, such as nickel, magnesium, and calcium. These ions act as molecular bridges, nestling inside the DNA grooves to lock the strands together, despite their naturally repelling charges. By combining direct imaging with sophisticated computer simulations, the researchers revealed the precise mechanics behind this seemingly impossible alignment.

Dr. Thomas Catley, co-lead author from the University of Sheffield, expressed excitement over directly visualizing this long-hypothesized mechanism. He emphasized that this discovery opens new avenues for studying other DNA interactions that were previously only theoretical. The findings also suggest that certain genomic regions may play a more significant role in DNA pairing, potentially becoming key areas of focus when mutations disrupt normal cellular processes, which are linked to cancer.

Professor Agnes Noy from the University of York, co-leader of the research, noted that this discovery could help identify regions of the genome specifically involved in DNA pairing. These regions might become particularly important when cellular processes go awry, contributing to diseases like cancer. The researchers confirmed a theory known as the DNA zipper model, first proposed over two decades ago by Professor Alexey Kornyshev and his colleagues.

This model posited that surrounding salt ions create alternating charge patterns, allowing DNA molecules to align like interlocking spiral staircases.

To validate this theory, the team employed atomic force microscopy to build topographical maps of DNA samples and detailed computer models to track the movement of individual atoms and ions. Their findings demonstrate that double-charged metal ions act like two charged arms, holding both DNA strands simultaneously across the gap.

Dr. Victor Velasco-Berrelleza, from the University of Sheffield's School of Mathematical and Physical Sciences, emphasized that while microscopy provides a visual snapshot, simulations uncover the underlying molecular mechanism, potentially becoming another tool in the DNA regulatory toolkit.