DNA is most commonly observed in a double-helix shape, but researchers in the lab have also seen it form into a four-stranded knot shape known as an i-motif. Now, for the first time, a new study in Nature Chemistry has shown that not only do i-motifs exist in human cells, but that they may be common, reports the Los Angeles Times.
Laurence Hurley, a professor of medical chemistry at the University of Arizona who was not involved in the study, tells the paper that the study lends credence to the idea that unusual DNA shapes may play an essential role in human biology. I-motifs may help the body control when genes make proteins, he said.
Not just any piece of DNA can fold itself into the i-motif shape, the LA Times notes. There must be a specific sequence of letters that include several cytosines. I-motifs are also dynamic, folding and unfolding depending on the acidity of their surroundings. Further, the article adds, the sequences that code for i-motifs are generally found not within a gene itself. Instead, they're found upstream in promoter regions.
This suggests that i-motifs may be used as a type of switch that can regulate gene expression, University of Mississippi biochemist Randy Wadkins tells the LA Times. He also added that certain stressors could possibly cause the acidity of the cell to change and prompt an i-motif to form, which could then trigger an over-expression or an under-expression of a nearby gene.
However, it is also possible that these i-motifs do nothing at all, the paper notes, and that these are just strange structures scientists have discovered that serve no purpose at all. Either way, Wadkins says, more research is needed.