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 Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

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 “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>