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 In focus: Peptides, the “little brothers and sisters” of proteins
12.11.2018 | Technische Universität Berlin

nachricht How to produce fluorescent nanoparticles for medical applications in a nuclear reactor
09.11.2018 | Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

Im Focus: Nanorobots propel through the eye

Scientists developed specially coated nanometer-sized vehicles that can be actively moved through dense tissue like the vitreous of the eye. So far, the transport of nano-vehicles has only been demonstrated in model systems or biological fluids, but not in real tissue. The work was published in the journal Science Advances and constitutes one step further towards nanorobots becoming minimally-invasive tools for precisely delivering medicine to where it is needed.

Researchers of the “Micro, Nano and Molecular Systems” Lab at the Max Planck Institute for Intelligent Systems in Stuttgart, together with an international...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

In focus: Peptides, the “little brothers and sisters” of proteins

12.11.2018 | Life Sciences

Materials scientist creates fabric alternative to batteries for wearable devices

12.11.2018 | Materials Sciences

A two-atom quantum duet

12.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>