Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

In potentially important discovery, scientists find two forms of genetic material chromatin

14.05.2003


Biologists have discovered what appear to be fundamental differences in the physical properties of the genetic material known as chromatin. Chromatin packages DNA into cells, and the scientists found the differences between chromatin that packages genes and the chromatin that packages DNA with regulatory or unknown functions.



The variation represents a previously unrecognized level of genomic organization and complexity, the scientists report, one that may exist in all cells with nuclei.

Made in yeast, the discovery offers broad potential uses, said Dr. Jason D. Lieb, a University of North Carolina at Chapel Hill biologist and a report author.


"For example, in pathology laboratories, differences in chromatin shape and structure in mammalian cells are routinely determined by staining tissues and observing them under a microscope," said Lieb, also a Carolina Center for the Genome Sciences researcher. "This is an important assay used to identify specific cell types and malignancies. It is possible that a detailed genomic view of these variations, provided by the method we describe in our paper, could be used to diagnose and sub-type cancer and other diseases."

It also could be an important tool for assigning functions to subsections of the genome, particularly for finding active genes, which remains a difficult problem, he said.

The report will appear online this week and in the May 27 issue of the Proceedings of the National Academy of Sciences. Other authors, all at Stanford University, are Drs. Peter L. Nagy and Michael L. Cleary of pathology and Dr. Patrick O. Brown of biochemistry.

"If the DNA from a single human chromosome were stretched and measured end-to-end, it would extend to over half an inch in length," Lieb said. "Our cells are much, much smaller than that, of course, and in order to fit inside the cell’s nucleus, which is even smaller, DNA must be compacted about 1,000-fold relative to its stretched-out length. This compaction is achieved by coiling and folding the DNA around proteins."

Together, he said, DNA and proteins are called chromatin, and it is chromatin that one sees in the familiar microscopic images of chromosomes. The basic unit of chromatin is called the nucleosome, which is like a barrel, and DNA is wrapped around that barrel 1.7 times. Nucleosomes are made up of proteins called histones, which come in many different "flavors."

"They can be modified by chemical processes known as methylation, acetylation and phosphorylation at different positions," Lieb said. "It has become increasingly clear that specific combinations of histone modifications are linked to underlying gene activity."

Based on its emerging importance, the information stored in histones and their modifications has been dubbed the "histone code," he said.

Packaging DNA serves not only to compact it but also has a key role in determining if the genes are turned on or off, the scientist said. Packaging DNA into chromatin acts as a gatekeeper, determining which parts of the genome are accessible to regulatory proteins and which parts are off limits. Defects in the proteins that organize DNA lead to embryonic development defects due to their influence on underlying gene activity.

That the DNA sequence in the genome is organized into two broad classes, genes and non-protein coding regions -- sometimes called "junk DNA" -- has been known for a long time, Lieb said. Much less is known about how chromatin is organized along the underlying DNA. "We initially set out to investigate the global distribution of a particular ’flavor’ of one histone in yeast," he said. "In the procedure, we crosslinked, or fixed, the yeast with formaldehyde, and then later were to reverse those crosslinks with heat. We inadvertently omitted the reversal, a key step in the technique, however. "We found then that by using formaldehyde-crosslinked chromatin in a biochemical procedure normally used to separate all proteins from all DNA, we could instead separate yeast chromatin into two specific and functionally distinct parts."

The most striking aspect of the result, he said, is that local variation in chromatin composition and structure is extremely diverse and complex, yet the new studies reveal what appears to be a global pattern that systematically and simply demarcates sequences in a way that reflects their assigned role as genes or non-genes.

"This method, or a similar method, may be applicable to other organisms," Lieb said "Our approach has potential use as a tool for describing changes in chromatin structure that accompany different genetic, environmental, and disease states."


Note: Lieb can be reached at (919) 843-3228 or jlieb@bio.unc.edu
Contact: David Williamson (919) 962-8596


David Williamson | EurekAlert!
Further information:
http://www.unc.edu/

More articles from Life Sciences:

nachricht Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory

nachricht Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>