Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microbe may explain evolutionary origins of DNA folding

11.08.2017

In the cells of palm trees, humans, and some single-celled microorganisms, DNA gets bent the same way. Now, by studying the 3-D structure of proteins bound to DNA in microbes called Archaea, University of Colorado Boulder and Howard Hughes Medical Institute (HHMI) researchers have turned up surprising similarities to DNA packing in more complicated organisms.

"If you look at the nitty gritty, it's identical," said Karolin Luger, a professor of Chemistry and Biochemistry at the University of Colorado Boulder and an HHMI Investigator. "It just blows my mind."


Archaea wrap their DNA (yellow) around proteins called histones (blue), shown above in a 3-D representation. The wrapped structure bears an uncanny resemblance to the eukaryotic nucleosome, a bundle of eight histone proteins with DNA spooled around it. But unlike eukaryotes, archaea wind their DNA around just one histone protein, and form a long, twisting structure called a superhelix.

Credit: Francesca Mattiroli

The archaeal DNA folding, described today in the journal 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, Arachaea represent one of the three domains of life. But Archaea are thought to include the closest living relatives to an ancient ancestor that first hit on the idea of folding DNA.

Scientists have long known that cells in all eukaryotes, from fish to trees to people, pack DNA in exactly the same way. DNA strands are wound around a 'hockey puck' composed of eight histone proteins, forming what's called a nucleosome. Nucleosomes are strung together on a strand of DNA, forming a "beads on a string" structure. The universal conservation of this genetic necklace raises the question of its origin.

If all eukaryotes have the same DNA bending style, "then it must have evolved in a common ancestor," said study co-author John Reeve, a microbiologist at Ohio State University. "But what that ancestor was, is a question no one asked."

Earlier work by Reeve had turned up histone proteins in archaeal cells. But, archaea are prokaryotes (microgorganisms without a defined nucleus), so it wasn't clear just what those histone proteins were doing. By examining the detailed structure of a crystal that contained DNA bound to archaeal histones, the new study reveals exactly how DNA packing works.

Luger and her colleagues wanted to make crystals of the histone-DNA complex in Methanothermus fervidus, a heat-loving archaeal species. Then, they wanted to bombard the crystals with X-rays. This technique, called X-ray crystallography, yields precise information about the position of each and every amino acid and nucleotide in the molecules being studied. But growing the crystals was tricky (the histones would stick to any given stretch of DNA, making it hard to create consistent histone-DNA structures), and making sense of the data they could get was no easy feat.

"It was a very gnarly crystallographic problem," said Luger.

Yet Luger and her colleagues persisted. The researchers revealed that despite using a single type of histone (and not four as do eukaryotes), the archaea were folding DNA in a very familiar way, creating the same sort of bends as those found in eukaryotic nucleosomes.

But there were differences, too. Instead of individual beads on a string, the archaeal DNA formed a long superhelix, a single, large curve of already twisty DNA strands.

"In Archaea, you have one single building block," Luger said. "There is nothing to stop it. It's almost like it's a continuous nucleosome, really."

This superhelix formation, it turns out, is important. When CU Boulder postdoctoral researcher Francesca Mattiroli, together with Thomas Santangelo's lab at Colorado State University, created mutations that interfered with this structure, the cells had trouble growing under stressful conditions. What's more, the cells seemed to not be using a set of their genes properly.

"It's clear with these mutations that they can't form these stretches," Mattiroli said.

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 said.

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.

###

*This release was written by the Howard Hughes Medical Institute and is re-used with permission.*

Howard Hughes Medical Institute | EurekAlert!

Further reports about: DNA DNA strands Eukaryotes crystals histone proteins proteins

More articles from Life Sciences:

nachricht Enduring cold temperatures alters fat cell epigenetics
19.04.2018 | University of Tokyo

nachricht Full of hot air and proud of it
18.04.2018 | University of Pittsburgh

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

Im Focus: The Future of Ultrafast Solid-State Physics

In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.

Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Diamond-like carbon is formed differently to what was believed -- machine learning enables development of new model

19.04.2018 | Materials Sciences

Electromagnetic wizardry: Wireless power transfer enhanced by backward signal

19.04.2018 | Physics and Astronomy

Ultrafast electron oscillation and dephasing monitored by attosecond light source

19.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>