Featured Research

from universities, journals, and other organizations

Stressed Cells Spark DNA Repair Missteps And Speed Evolution

Date:
September 16, 2005
Source:
Baylor College of Medicine
Summary:
When Dr. Susan Rosenberg, professor of molecular and human genetics at Baylor College of Medicine, first published her finding that the mutation rate increased in bacteria stressed by starvation, sometimes resulting in a rare change that benefited the bacteria, it was controversial. In a report in the current issue of the journal Molecular Cell, she and her colleagues describe not only how it happens but also show that this only occurs at a special time and place in the stressed cells.

HOUSTON -- (Sept. 16, 2005) -- When Dr. Susan Rosenberg, professor of molecular and human genetics at Baylor College of Medicine, first published her finding that the mutation rate increased in bacteria stressed by starvation, sometimes resulting in a rare change that benefited the bacteria, it was controversial.

In a report in the current issue of the journal Molecular Cell, she and her colleagues describe not only how it happens but also show that this only occurs at a special time and place in the stressed cells.

It all begins with the way that the cell repairs breaks in the double strands of DNA that are its genetic blue print. Usually, when this happens, special protein machinery in the cell copies the missing DNA from another chromosome and rejoins the broken ends around the newly synthesized genetic material.

"It fixes the hole in the DNA by copying similar information," said Rosenberg. However, when the process goes wrong, the repair process introduces errors into the DNA.

When graduate student Rebecca G. Ponder set up a system so that she could control where the break in DNA occurred, she found that errors occurred right next to the break in the stressed cells, and that the rate of errors was 6,000 fold higher than in cells whose DNA was not broken. "It's really about local repair," said Rosenberg. Not only that, but subsequent experiments proved that this mechanism of increased mutation at sites of DNA repair occurs only in the cells under stress. "Even if you get a break in a cell, it won't process it in a mutagenic way," said Rosenberg. "The cell repairs it, but does not make mutations unless the cell is stressed."

The findings support the notion that the increased mutation rate may give the cells a selective advantage, she said. Faced with starvation, most cells do not increase their mutation rate. Then if food becomes available again, they do well.

Among the small percentage that do increase mutations, most of the errors are neutral, not affecting cells at all. Many are deleterious, resulting in cell death. But a small percentage is advantageous, allowing the cells to survive in an adverse environment.

The fact that the changes in the rate of mutation occur only in a certain physical space at a certain time gives the cells advantage because it reduces the risk to the whole colony. DNA breaks occur only rarely in each individual cell. If the mutations are restricted in time and space, it reduces the risk that the mistakes in repair will affect some other gene. It can also enhance the likelihood of two mutations occurring in the same gene or neighboring genes.

"This can speed evolution of complex protein machines." Rosenberg said.

###

Natalie C. Fonville also contributed to this research, which was supported by grants from the U.S. Department of Defense Breast Cancer Research Program and the National Institutes of Health.


Story Source:

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


Cite This Page:

Baylor College of Medicine. "Stressed Cells Spark DNA Repair Missteps And Speed Evolution." ScienceDaily. ScienceDaily, 16 September 2005. <www.sciencedaily.com/releases/2005/09/050916080112.htm>.
Baylor College of Medicine. (2005, September 16). Stressed Cells Spark DNA Repair Missteps And Speed Evolution. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2005/09/050916080112.htm
Baylor College of Medicine. "Stressed Cells Spark DNA Repair Missteps And Speed Evolution." ScienceDaily. www.sciencedaily.com/releases/2005/09/050916080112.htm (accessed September 19, 2014).

Share This



More Plants & Animals News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
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

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