Featured Research

from universities, journals, and other organizations

Protein maintains order in the nucleus

Date:
April 4, 2013
Source:
Max-Planck-Gesellschaft
Summary:
Two meters of DNA are packed into the cell nucleus, presumably based on a strictly defined arrangement. Researchers have now succeeded in explaining a phenomenon, which was first observed 40 years ago. Researchers have identified a protein responsible for the correct arrangement of the chromosome centromeres in the nucleus.

Order in the nucleus: Centromeres (marked in green) of the 13 Drosophila tissue culture chromosomes are clustered at only 3 positions. They attach to the nuclear region called nucleolus (dark spot). Chromatin is stained in red and marks the nucleus.
Credit: Patrick Heun, MPI of Immunobiology and Epigenetics

Two metres of DNA are packed into the cell nucleus, presumably based on a strictly defined arrangement. Researchers working with biologist Patrick Heun from the Max Planck Institute of Immunobiology and Epigenetics in Freiburg have now succeeded in explaining a phenomenon, which was first observed 40 years ago. The centromeres, namely the structures at the primary constriction of the X-shaped chromosomes, are clustered in a few specific locations in the cell nucleus. Using fruit flies as a model, the researchers have shown that a single protein plays a key role in this process. If this protein is missing, DNA damage in the cell increases and cell division is impaired.

Each chromosome is duplicated before cell division. However, the two copies remain connected at a single site, the centromere, until shortly before division. This gives rise to the classical X-shaped structure of chromosomes. Over the past 40 years, dye experiments have shown that in many organisms and different cell types, the centromeres of several chromosomes are clustered in the nucleus. However, it is still little understood how the DNA is organized in the nucleus.

In a series of experiments using the fruit fly Drosophila melanogaster, Patrick Heun and colleagues at the Max Planck Institute of Immunobiology and Epigenetics and associated with cluster of excellence BIOSS Centre for Biological Signalling Studies of the University of Freiburg, have now shown that the protein NLP plays a major role for centromere positioning. It binds specifically to the centromere region of the chromosomes and causes their clustering near the nucleolus, an important area of the nucleus. The site where the protein binds to the chromosome depends on the packaging of the DNA. As Heun and his team discovered, however, the DNA sequence at this site does not appear to matter. NLP also exists in a slightly modified form in humans and is known as nucleophosmin.

If the researchers eliminate the NLP protein using the so-called gene knockdown method, the centromeres fall apart and distribute themselves throughout the nucleus. Due to this change in the spatial architecture of the nucleus, silenced areas of DNA are activated and damage accumulates in the DNA double-strand. Such changes can impair the stability of the genome and ultimately contribute to the emergence of cancer. "It is already known that the organisation of the nucleus plays a role in a specific form of leukemia. It would be very interesting to find out whether the lack of organisation of the centromeres also plays a role in cancer cells," says Heun.

In addition to the protein NLP, the scientists also succeeded in decoding the interactions with two other already known proteins. The nucleolus protein modulo anchors the complex consisting of the centromere and NLP to the nucleolus, and the protein CTCF supports NLP in the clustering of the centromeres.

"Regarding the molecular mechanism underlying this phenomenon, we now have a foot in the door," says Heun. He has been working on the elucidation of this process with his doctoral student Jan Padeken and his team since 2008. Other studies on Drosophila and mammalian cells, for example from mice, are now expected to follow. "We anticipate that other proteins are also involved in the organisation of the centromeres and would like to find out whether the discovered protein network also plays a role in other organisms," says Heun.


Story Source:

The above story is based on materials provided by Max-Planck-Gesellschaft. Note: Materials may be edited for content and length.


Journal Reference:

  1. Padeken J, José Mendiburo M, Chlamydas S, Schwarz H-J, Kremmer E, and Heun P. The Nucleoplasmin homologue NLP mediates centromere clustering and anchoring to the nucleolus. Molecular Cell, 2013 (in press)

Cite This Page:

Max-Planck-Gesellschaft. "Protein maintains order in the nucleus." ScienceDaily. ScienceDaily, 4 April 2013. <www.sciencedaily.com/releases/2013/04/130404121930.htm>.
Max-Planck-Gesellschaft. (2013, April 4). Protein maintains order in the nucleus. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2013/04/130404121930.htm
Max-Planck-Gesellschaft. "Protein maintains order in the nucleus." ScienceDaily. www.sciencedaily.com/releases/2013/04/130404121930.htm (accessed September 18, 2014).

Share This



More Plants & Animals News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Chimp Violence Study Renews Debate On Why They Kill

Chimp Violence Study Renews Debate On Why They Kill

Newsy (Sep. 17, 2014) The study weighs in on a debate over whether chimps are naturally violent or become that way due to human interference in the environment. Video provided by Newsy
Powered by NewsLook.com
Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins