Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study helps explain gene silencing in the developing embryo

29.10.2002


New research at the University of North Carolina sheds light on the process that silences a group of genes in the developing embryo.



Down regulation of gene expression or "gene silencing" is considered crucial in normal development. In the embryo, proteins expressed by different sets of genes help signal the pattern of development, including limb formation. However, when that work is completed, the genes responsible must be turned off, explains Dr. Yi Zhang, assistant professor of biochemistry and biophysics at UNC-Chapel Hill School of Medicine and a member of the Lineberger Comprehensive Cancer Center.

"During the early embryonic development, a group of genes called Hox genes needs to be expressed. After they’ve been expressed and have set the body pattern, they have to be silenced permanently during the life of the organism," Zhang said.


According to Zhang, another gene group known as the Polycomb group has been intensely studied for its role in silencing Hox in organisms ranging from flies to mammals, including humans. "We know that if something is wrong with the Polycomb group, if these genes are mutated and cannot silence Hox, then development becomes abnormal."

Writing in the Nov 1 issue of Science, Zhang and co-authors from UNC; Southern Methodist University, Dallas, Texas; and Memorial Sloan Kettering Cancer Center, New York, NY, report the purification and characterization of a Polycomb group protein complex. Importantly, their research has established a link between Polycomb gene silencing and histone protein methylation, the addition of a methyl group to lysine, one of the amino acids that comprise the tail region of histone molecules.

Four core histone proteins are highly conserved in eukaryotic organisms, those having nucleated cells. These histones are involved in packaging our genetic information, DNA. Each contain a globular domain and an amino terminal "tail." Of interest to Zhang and others at UNC and elsewhere is that histones, specifically processes that modify them including methylation, are thought to play a major role in gene expression and cell division.

"Basically, we found that the Polycomb proteins function through methylating a particular lysine residue, lysine 27, on histone 3," Zhang said. When enzyme activity causing methylation of this site is blocked, Hox gene silencing does not occur.

Given those findings, Zhang and his study team could explain the permanence of Hox gene silencing. "Histone methylation cannot be reversed. It becomes permanent, a long-term genetic marker. Thus far, no ’histone demethylase’ has been discovered."

It may well be that methylation and other modifications of histone proteins are part of an emerging "histone code" of modifications that ultimately regulate gene expression. This code was postulated three years ago by Drs. David Allis and Brian Strahl at the University of Virginia. (Strahl is now at UNC.) Currently under investigation by Zhang and colleagues in several departments at UNC, a histone code would be in addition to the now familiar genetic code of repeating As, Cs, Gs, and Ts of DNA nucleotide sequences.

Through this histone code, differentially modified histone proteins could organize the genome into stretches of active and silent regions. Moreover, these regions would be inherited during cell division.

The study was supported by grants from the National Institute of General Medicine at NIH and the American Cancer Society.


note: contact Zhang at 919-843-8225 or yi_zhang@med.unc.edu
School of Medicine contact, Les Lang, 919-843-9687 or llang@med.unc.edu

Leslie Lang | EurekAlert!
Further information:
http://www.med.unc.edu/

More articles from Life Sciences:

nachricht Individual Receptors Caught at Work
19.10.2017 | Julius-Maximilians-Universität Würzburg

nachricht Rapid environmental change makes species more vulnerable to extinction
19.10.2017 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>