Featured Research

from universities, journals, and other organizations

Exploding Chromosomes Fuel Research About Evolution Of Genetic Storage

Date:
August 24, 2008
Source:
University of Chicago
Summary:
Research into single-celled, aquatic algae called dinoflagellates is showing that these and related organisms may have evolved more than one way to tightly pack their DNA into chromsomes. Even so, the evolution of chromosomes in dinoflagellates, humans and other mammals seem to share a common biochemical basis.

This false-color image of the distribution of calcium in the chromosomes of a deer was obtained using secondary ion mass spectrometry with the University of Chicago's high-resolution scanning ion microprobe.The same technique applied to single-celled organisms called dinoflagellates are providing new insights into the evolution of chromosomes.
Credit: Courtesy of Riccardo Levi-Setti

Human cells somehow squeeze two meters of double-stranded DNA into the space of a typical chromosome, a package 10,000 times smaller than the volume of genetic material it contains.

"It is like compacting your entire wardrobe into a shoebox," said Riccardo Levi-Setti, Professor Emeritus in Physics at the University of Chicago.

Now research into single-celled, aquatic algae called dinoflagellates is showing that these and related organisms may have evolved more than one way to achieve this feat of genetic packing. Even so, the evolution of chromosomes in dinoflagellates, humans and other mammals seem to share a common biochemical basis, according to a team Levi-Setti led. The team's findings appear online, in Science Direct's list of papers in press in the European Journal of Cell Biology.

Packing the whole length of DNA into tiny chromosomes is problematic because DNA carries a negative charge that, unless neutralized, prevents any attempt at folding and coiling due to electrostatic repulsion. The larger the quantity of DNA, the more negative charge must be neutralized along its length.

"Dinoflagellates have much more nuclear DNA than humans," said Texas A&M biologist Peter Rizzo, who collaborated on the research with Levi-Setti and Konstantin Gavrilov, a Visiting Research Scientist in the Enrico Fermi Institute at the University of Chicago.

Every bit of DNA must be properly duplicated and divided to facilitate reproduction and growth. In humans and mammals, proteins called histones partially neutralize the DNA's negative charge. When histones wrap themselves in DNA, they become nucleosomes.

Dinoflagellates are stuffed at the core with tightly compacted chromosomes, yet these organisms contain neither histones nor nucleosomes. "What takes care of neutralizing DNA, to allow chromosomes to condense?" Levi-Setti asked. "Most biology books do not tell you."

Other scientists had already identified positively charged atoms called cations as neutralizing factors. They found that dinoflagellate chromosomes explode upon the removal of calcium and magnesium cations.

Levi-Setti has produced the first images of the distribution of these cations in dinoflagellate chromosomes. These images verify that cations, mainly of calcium and magnesium, neutralize DNA's enormous negative charge, and further suggest a critical role in folding the protein as well.

The finding raises questions about the evolution of chromosomes, Rizzo said. "Did dinoflagellates once have histones and then lost them? Or did dinoflagellates never have histones and just 'figured out' a different way to fold large amounts of DNA into chromosomes?" Rizzo asked.

The images were produced using a high-resolution scanning ion microprobe, an instrument that Levi-Setti developed in the 1980s jointly with Hughes Research Laboratories in Malibu, Calif. For the last 15 years, Levi-Setti has collaborated with associates of pioneering chromosome researcher Janet Rowley, the Blum-Riese Distinguished Service Professor in Medicine, Molecular Genetics & Cell Biology and Human Genetics at the University of Chicago.

In 2001, the collaboration demonstrated that cations play an important role in compacting mammalian DNA and helping chromosomes maintain their structure. "Chromosomes would fall apart when calcium and magnesium were removed," Levi-Setti said.

Wondering if there could be a fundamental evolutionary process at work, Levi-Setti extended his research to the fruit fly. Like mammals, fruit flies belong to the pantheon of eukaryotes. In contrast to prokaryotes like bacteria, eukaryotes pack their genetic material in a cellular nucleus. Prokaryotes lack a nucleus.

"Cations play a very important role in the folding and charge neutralization of DNA in all eukaryotes, but more so in dinoflagellates," Rizzo said. "I find it truly amazing that in all other eukaryotes, histones help in this charge neutralization, and dinoflagellates constitute the only exception to this nearly universal rule. It looks like this may have been the first and very efficient step toward the goal of neutralizing DNA, long before histones came into play."


Story Source:

The above story is based on materials provided by University of Chicago. Note: Materials may be edited for content and length.


Journal Reference:

  1. Riccardo Levi-Setti, Konstantin L. Gavrilov and Peter J. Rizzo. Divalent cation distribution in dinoflagellate chromosomes imaged by high-resolution ion probe mass spectrometry. European Journal of Cell Biology, 2008; (in press) DOI: 10.1016/j.ejcb.2008.06.002

Cite This Page:

University of Chicago. "Exploding Chromosomes Fuel Research About Evolution Of Genetic Storage." ScienceDaily. ScienceDaily, 24 August 2008. <www.sciencedaily.com/releases/2008/08/080821164306.htm>.
University of Chicago. (2008, August 24). Exploding Chromosomes Fuel Research About Evolution Of Genetic Storage. ScienceDaily. Retrieved August 30, 2014 from www.sciencedaily.com/releases/2008/08/080821164306.htm
University of Chicago. "Exploding Chromosomes Fuel Research About Evolution Of Genetic Storage." ScienceDaily. www.sciencedaily.com/releases/2008/08/080821164306.htm (accessed August 30, 2014).

Share This




More Plants & Animals News

Saturday, August 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Newsy (Aug. 29, 2014) In a new study, a promising experimental treatment for Ebola managed to cure a group of infected macaque monkeys. Video provided by Newsy
Powered by NewsLook.com
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

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