Featured Research

from universities, journals, and other organizations

No evidence for 30-nm chromatin fibres in the mouse genome

Date:
October 4, 2012
Source:
EMBO - excellence in life sciences
Summary:
Scientists have used three-dimensional imaging techniques to settle a long-standing debate about how DNA and structural proteins are packaged into chromatin fibers. The researchers revealed that the mouse genome consists of 10-nm chromatin fibers but did not find evidence for the wider 30-nm fibers that were previously thought to be important components of the DNA architecture.

DNA packaged into 10-nm chromatin fibres.
Credit: Uta Mackensen, EMBO

Scientists in Canada and the United States have used three-dimensional imaging techniques to settle a long-standing debate about how DNA and structural proteins are packaged into chromatin fibres. The researchers, whose findings are published in EMBO reports, reveal that the mouse genome consists of 10-nm chromatin fibres but did not find evidence for the wider 30-nm fibres that were previously thought to be important components of the DNA architecture.

"DNA is an exceptionally long molecule that can reach several metres in length. This means it needs to be packaged into a highly compact state to fit within the limited space of the cell nucleus," said David Bazett-Jones, Senior Scientist at the Hospital for Sick Children, Toronto, and Professor at the University of Toronto, Canada. "For the past few decades, scientists have favoured structural models for chromatin organization where DNA is first wrapped around proteins in nucleosomes. In one possible model, the strand of repeating nucleosomes is wrapped further into a higher-order thick 30-nm fibre. In a second model, the 30-nm fibre is not required to compact the DNA. Differences between these models have implications for the way the cell regulates the transcription of genes."

Chromatin is the complex of DNA and proteins that is the fundamental constituent of chromosomes in the nucleus of the cell. The researchers used a combination of state-of-the-art imaging techniques, in this case energy spectroscopic imaging and electron tomography, to generate high-resolution three-dimensional images of chromatin in mouse cells. This approach allows for visual analysis of chromatin fibres without the need to add chemical agents to improve the contrast of images.

"Our results revealed that the 30-nm chromatin fibre model is not consistent with the structure we found in our three-dimensional spectroscopic images," said Bazett-Jones. "It was previously thought that the transition between thinner and thicker fibres represented a change from an active to repressed state of chromatin. However, our inability to detect 30-nm fibres in the mouse genome leads us to conclude that the transcriptional machinery has widespread access to the DNA packaged into chromatin fibres."

The results are consistent with recent studies of the human genome which suggest that approximately 80% of the genome contains elements that are linked to biological function. Access to enhancers, promoters and other regulatory sequences on such a wide region of the genome means that all of these sites must be accessible. The 10-nm model of chromatin fibres provides sufficient access to DNA to allow potential target sites to be reached. The 30-nm model would not accommodate such widespread access.

The researchers offer several reasons for the observation of wider fibres in earlier studies. In some cases, the conditions outside of the cell, including those used in earlier studies where chromatin was extracted from the cell, may have given rise to structural artifacts. For some of the earlier spectroscopic studies, it may even be a question of poor resolution of existing 10-nm fibres.


Story Source:

The above story is based on materials provided by EMBO - excellence in life sciences. Note: Materials may be edited for content and length.


Journal Reference:

  1. Eden Fussner, Mike Strauss, Ugljesa Djuric, Ren Li, Kashif Ahmed, Michael Hart, James Ellis, David P Bazett-Jones. Open and closed domains in the mouse genome are configured as 10-nm chromatin fibres. EMBO reports, 2012; DOI: 10.1038/embor.2012.139

Cite This Page:

EMBO - excellence in life sciences. "No evidence for 30-nm chromatin fibres in the mouse genome." ScienceDaily. ScienceDaily, 4 October 2012. <www.sciencedaily.com/releases/2012/10/121004093045.htm>.
EMBO - excellence in life sciences. (2012, October 4). No evidence for 30-nm chromatin fibres in the mouse genome. ScienceDaily. Retrieved August 28, 2014 from www.sciencedaily.com/releases/2012/10/121004093045.htm
EMBO - excellence in life sciences. "No evidence for 30-nm chromatin fibres in the mouse genome." ScienceDaily. www.sciencedaily.com/releases/2012/10/121004093045.htm (accessed August 28, 2014).

Share This




More Plants & Animals News

Thursday, August 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Raw: Australian Sheep Gets Long Overdue Haircut

Raw: Australian Sheep Gets Long Overdue Haircut

AP (Aug. 28, 2014) Hoping to break the record for world's wooliest, Shaun the sheep came up 10 pounds shy with his fleece weighing over 50 pounds after being shorn for the first time in years. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Minds Blown: Scientists Develop Fish That Walk On Land

Minds Blown: Scientists Develop Fish That Walk On Land

Newsy (Aug. 28, 2014) Canadian scientists looking into the very first land animals took a fish out of water and forced it to walk. Video provided by Newsy
Powered by NewsLook.com
Fake Dogs Scare Real Geese from Wis. Park

Fake Dogs Scare Real Geese from Wis. Park

AP (Aug. 28, 2014) Parks officials in Stevens Point, Wisconsin had a fowl problem. Canadian Geese were making a mess of a park, so officials enlisted cardboard versions of man's best friend. (Aug. 28) 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