Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The genetic transmission of gene locks

20.03.2017

Although all cells in an organism contain the same genes, only some of the genes are activated in a given cells and others remain inactive. Genes coil around histone proteins in the form of DNA threads. If a gene has to remain inactive, its histones are marked by the PRC2 enzyme so that this gene is locked down and cannot be read. When cells divide and the genes are copied, these histone marks must be placed again, at exactly the same location. The mechanism that enables transmission of this information has now been explained by Jürg Müller from the Max Planck Institute of Biochemistry in Martinsried in a study published in the journal Science.

In animals and plants, the genomic DNA in the cell nucleus is wrapped around small proteins known as histones. Jürg Müller, Leader of the Biology of Chromatin Research Group at the MPI of Biochemistry explains: “The DNA is like a big library of books. Each book contains the instruction manual for making a protein. Although the same DNA library is present in all cells, some of the books are ‘sealed’, so they cannot be read. A muscle cell requires other protein-building instructions than an intestinal cell.”


Like a sealed book, some genes from the DNA library cannot be read as, depending on the cell type, only certain genes are needed. The enzyme PRC2 helps with the “sealing” of genes in the cells.

Illustration: Monika Krause © MPI of Biochemistry

An essential mechanism to prevent the expression of genes relies on the chemical marking of histone proteins to permanently “lock down” genes. In the current study, Müller and his team examined how such gene locks are transmitted during cell division.

Histones play a key role in determining how accessible a gene is. When genes need to be permanently locked down, their histones are chemically modified by the enzyme PRC2. “If we imagine the histones as the binder of the book, PRC2 helps to seal that book and prevent that it gets opened and read,” explains Müller.

During cell division, the information about whether a gene needs to remain active or inactive in a given cell has to be transmitted to the daughter cells – or, to continue with the metaphor: All books must be copied and the two copies of certain books must remain sealed. However, the histones available in the mother cell are not sufficient for this and new histones must be added - so that the books do not fall apart.

“We investigated how marked histone proteins present at a gene are distributed during cell division and how newly incorporated histones then become marked by PRC2,” says Müller. The scientists discovered that marked histones are distributed in a random manner to the two gene copies in daughter cells. PRC2 then must first bind to specific sequences in the DNA of that gene in order to mark the new histones.

“If that DNA, called Polycomb Response Element, is removed from a gene, PRC2 cannot mark the new histones and the only marked histones left are the ones from the mother cell. So with each cell division, the amount of marked histones is further diluted and, after a few divisions, they are completely eliminated,” explains Friederike Laprell, first author of the study.

When a cell cannot keep certain books sealed and the instructions in those books become available to a cell, the cell quickly starts to lose or change its identity - a process that results in diseases like cancer. “So it is PRC2 together with the Polycomb Response Element DNA that is present in certain genes that ensures that cells can maintain and propagate their identity for many cell generations,” summarizes Müller.

Original publication:
F. Laprell, K. Finkl and J. Müller: Propagation of Polycomb-repressed chromatin requires sequence-specific recruitment to DNA, Science, March 2017
DOI: 10.1126/science.aai8266

Contact:
Dr. Jürg Müller
Chromatin Biology
Max Planck Institute of Biochemistry
Am Klopferspitz 18
82152 Martinsried
E-Mail: muellerj@biochem.mpg.de
www.biochem.mpg.de/mueller

Dr. Christiane Menzfeld
Public Relations
Max Planck Institute of Biochemistry
Am Klopferspitz 18
82152 Martinsried
Germany
Tel. +49 89 8578-2824
E-Mail: pr@biochem.mpg.de
www.biochem.mpg.de

Weitere Informationen:

http://www.biochem.mpg.de/en - homepage max planck institute of biochemistry
http://www.biochem.mpg.de/en/rg/mueller - homepage Jürg Müller

Dr. Christiane Menzfeld | Max-Planck-Institut für Biochemie

More articles from Life Sciences:

nachricht Are there sustainable solutions in dealing with dwindling phosphorus resources?
16.10.2017 | Leibniz-Institut für Nutzierbiologie (FBN)

nachricht Strange undertakings: ant queens bury dead to prevent disease
13.10.2017 | Institute of Science and Technology Austria

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

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...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

Im Focus: Small collisions make big impact on Mercury's thin atmosphere

Mercury, our smallest planetary neighbor, has very little to call an atmosphere, but it does have a strange weather pattern: morning micro-meteor showers.

Recent modeling along with previously published results from NASA's MESSENGER spacecraft -- short for Mercury Surface, Space Environment, Geochemistry and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

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

Conference Week RRR2017 on Renewable Resources from Wet and Rewetted Peatlands

28.09.2017 | Event News

 
Latest News

A single photon reveals quantum entanglement of 16 million atoms

16.10.2017 | Physics and Astronomy

The melting ice makes the sea around Greenland less saline

16.10.2017 | Earth Sciences

On the generation of solar spicules and Alfvenic waves

16.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>