DNA folding is an incredibly important control mechanism. That’s because every single cell in our body contains around 2 metres of DNA, so to fit inside us, it has to be tightly wrapped up into a bundle called a nucleosome – like a thread around a spool.
And the way the DNA is wrapped up controls which genes are ‘read’ by the rest of the cell – genes that are all wrapped on the inside won’t be expressed as proteins, but those on the outside will. This explains why different cells have the same DNA but different functions.
In recent years, biologists have even started to isolate the mechanical cues that determine the way DNA is folded, by ‘grabbing onto’ certain parts of the genetic code or changing the shape of the ‘spool’ the DNA is wrapped around. So far, so good, but what do theoretical physicists have to do with all this?
A team from Leiden University in the Netherlands has now been able to step back and look at the process on a whole-genome scale, and back up through computer simulations that these mechanical cues are actually coded into our DNA. The physicists, led by Helmut Schiessel, did this by simulating the genomes of both baker’s yeast and fission yeast, and then randomly assigning them a second level of DNA information, complete with mechanical cues.
They were able to show that these cues affected how the DNA was folded and which proteins are expressed – further evidence that the mechanics of DNA are written into our DNA, and they’re just as important in our evolution as the code itself. This means the researchers have shown that there’s more than one way that DNA mutations can affect us: by changing the letters in our DNA, or simply by changing the mechanical cues that arrange the way a strand is folded.
“The mechanics of the DNA structure can change, resulting in different packaging and levels of DNA accessibility,” they explain, “and therefore differing frequency of production of that protein.” Edited from: ScienceAlert