Human cells, hardy microbes share common ancestor
by Staff Writers
Fort Collins CO (SPX) Nov 10, 2017
To Tom Santangelo, single-celled microorganisms called archaea are like ancient mariners, surviving among the most extreme conditions on Earth, including volcanic vents in the deep ocean.
The Colorado State University researcher studies how these hardy microbes - which constitute one of three surviving domains of life - express their genes, produce their energy, and thrive in hot, lightless environments.
It turns out, we're not so different - biochemically, anyway - from archaea after all.
Santangelo, associate professor in the Department of Biochemistry and Molecular Biology, was on a team that found striking parallels between how archaeal cells and more complex cells, including humans' and animals', package and store their genetic material. The breakthrough study, published in Science earlier this year, provided evidence that archaea and eukaryotic cells share a common mechanism to compact, organize and structure their genomes.
The study was led by Karolin Luger, now a structural biologist at the University of Colorado Boulder. Most of the results reported in Science were completed while Luger was a CSU faculty member, from 1999 to 2015.
A little high school biology review: Eukaryotes are cells with a nucleus and membrane-bound organelles, and they include fungal, plant and animal - including human - cells. They're set apart from their less complex counterparts, prokaryotes, by the absence of a nucleus. While archaea and bacteria are both prokaryotes, they are only distantly related. Archaea are the likely progenitors of eukaryotes and share many of the same proteins that control gene expression.
One of life's most fundamental processes - the mechanics by which DNA bends, folds and crams itself into a cell nucleus - is common across all eukaryotes, from microscopic protists to plants to humans.
Packed inside the nucleus of every eukaryotic cell is several feet of genetic material that is compacted in a very specific way. Small sections of DNA are wrapped, like thread around a spool, roughly two times around eight small proteins called histones. This entire DNA-histone complex is called a nucleosome, and a string of compacted nucleosomes is called chromatin. In 1997, Luger and colleagues first reported the exact structure of eukaryotic nucleosomes via X-ray crystallography.
Science paper collaborator John Reeve had discovered in the 1990s that histone proteins were not limited to eukaryotes, but were also found in nucleus-free archaea cells. Reeve and Luger began a collaboration to crystallize histone-based archaeal chromatin and compare that structure with eukaryotic chromatin.
After years of stops and starts and trouble growing reliable archaeal histone crystals - Luger called it a "gnarly crystallographic problem" - the scientists succeeded in resolving the structure of archaeal chromatin, revealing its structural similarity to eukaryotes.
In the data, the archaeal DNA seemed to form long, curvy, repeating superhelices. The researchers weren't sure if the structure was real, or an artifact of the experiment. That's where Santagelo's team at CSU provided key expertise.
"My group took up the challenge of determining whether the structure resolved in the crystals represented a biologically meaningful structure," he said.
Santangelo's team made variants of the archaeal histones and tested how the cells fared, as they disrupted the DNA superhelix. They found that the more they destabilized the structure, the sicker the cells got. Their efforts underscored the merits of the structure Luger's group had determined.
Being part of a team that provided so fundamental an insight as the ancestry of our cells was among the most rewarding moments of Santangelo's career.
"The major impact of the paper, I think, is that the idea of compacting DNA into those structures is a very ancient idea - probably more than 1 billion years old," Santangelo said. "Histone proteins came on the scene, and once they got into and started packaging genomes, they largely made themselves indispensable to those cells that encoded them."
London, UK (SPX) Nov 08, 2017
Mammals only started being active in the daytime after non-avian dinosaurs were wiped out about 66 million years ago (mya), finds a new study led by UCL and Tel Aviv University's Steinhardt Museum of Natural History. A long-standing theory holds that the common ancestor to all mammals was nocturnal, but the new discovery reveals when mammals started living in the daytime for the first time ... read more
Colorado State University
Explore The Early Earth at TerraDaily.com
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.|