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 A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>