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 Copper hydroxide nanoparticles provide protection against toxic oxygen radicals in cigarette smoke
29.05.2017 | Johannes Gutenberg-Universität Mainz

nachricht Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Camera on NASA's Lunar Orbiter survived 2014 meteoroid hit

29.05.2017 | Physics and Astronomy

Strathclyde-led research develops world's highest gain high-power laser amplifier

29.05.2017 | Physics and Astronomy

A 3-D look at the 2015 El Niño

29.05.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>