By studying the 3-D structure of proteins bound to DNA in microbes called archaea, researchers have turned up surprising similarities to DNA packing in more complicated organisms. “If you look at the nitty gritty, it’s identical,” says Howard Hughes Medical Institute Investigator Karolin Luger, a structural biologist and biochemist at the University of Colorado Boulder. “It just blows my mind.”
The archaeal DNA folding, reported August 10 in Science, hints at the evolutionary origins of genome folding, a process that involves bending DNA and one that is remarkably conserved across all eukaryotes (organisms that have a defined nucleus surrounded by a membrane). Like Eukarya and Bacteria, Archaea represents one of the three domains of life. But Archaea is thought to include the closest living relatives to an ancient ancestor that first hit on the idea of folding DNA.
The results suggest that the archaeal DNA folding is an early prototype of the eukaryotic nucleosome. “I don’t think there’s any doubt that it’s ancestral,” Reeve says.
Still, many questions remain. Luger says she’d like to look for the missing link — a nucleosome-like structure that bridges the gap between the simple archaeal fold and the elaborate nucleosome found in eukaryotes, which can pack a huge amount of DNA into a small space and regulate gene behavior in many ways. “How did we get from here to there?” she asks. Paper. (paywall) – Francesca Mattiroli et al. Structure of histone-based chromatin in Archaea. Science, 2017 DOI: 10.1126/science.aaj1849 More.
If it’s that old, we run into the same “earlier than thought” problem we have often encountered: How did it get to be so complex so early if success depended entirely on random outcomes?
A friend observes that a mechanism complex organisms need is found long before they exist as well. It certainly sounds like a program.
See also: Advanced multicellular plant-like fossils appeared “much earlier than thought”
Earliest animals with true body cavities found at 30 mya earlier than thought
Stasis: Life goes on but evolution does not happen