For more than half a century, scientists believed they understood the basics of DNA and the genetic make-up of every living thing because of the Double Helix model first established by James D. Watson and Francis Crick in 1953. Under that model, all known living organisms were made up of molecules comprised of two strands of nucleotides filled with various genetic information. As it turns out, however, scientists may have been wrong to believe that everything was a double helix construction, especially now that the first quadruple helix has been discovered.
New Scientist has a report about the discovery of the helix, discovered by a team at the University of Cambridge headed up by Shankar Balasubramanian. The four-stranded cells – currently called G-quadruplexes – have been identified in human cancer cells, and although little is currently known for sure about them, Balasubramanian’s team believes that they are transitory structures that may be related to the sub-division of cells.
The report explains that the G-quadruplexes were discovered “with the help of an antibody that attached exclusives to G-quadruplexes.” The team worked to intentionally stop cells from unraveling to ordinary DNA with the use of a molecule called pyridostatin which “locks” the four-stranded helices whenever they appear. With the G-quadruplexes locked in this way, the team was able to count how many were formed at each stage of cell multiplication, resulting in more that appeared during the “s-phase,” or when cells are replicating DNA prior to separation. The G-quadruplexes appeared in chromosomes and telomeres, the protective caps on chromosomes.
“I hope our discovery challenges the dogma that we really understand DNA structure because Watson and Crick solved it in 1953,” Balasubramnian told New Scientist, while also putting forward the possibility that there is something about cancer cells in particular – which divide so quickly that they may be different from other cells – that makes them particularly susceptible to the four-stranded helix. “I expect they will also exist in normal cells, but I predict that there will be differences with cancer cells,” he said. “We plan to find out whether the quadruplexes are a natural nuisance, or there by design.”
The scale of this discovery is obviously massive. Given that all life was understood to be based upon double helix DNA, it really does have the feel of the traditional everything you know is wrong shock trailed in melodramatic movies and comic books – but is also understandably important in the ongoing fight against cancer. “This research further highlights the potential for exploiting these unusual DNA structures to beat cancer,” says Cancer Research UK’s Julie Sharp, which funded Balasubramanian’s research. “The next part of this is to figure out how to target them in tumor cells.”
