Featured Research

from universities, journals, and other organizations

Once-suspect Protein Found To Promote DNA Repair, Prevent Cancer

Date:
July 23, 2008
Source:
University of Texas M. D. Anderson Cancer Center
Summary:
An abundant chromosomal protein that binds to damaged DNA prevents cancer development by enhancing DNA repair, researchers report in the Proceedings of the National Academies of Science.

An abundant chromosomal protein that binds to damaged DNA prevents cancer development by enhancing DNA repair, researchers at The University of Texas M. D. Anderson Cancer Center report online in the Proceedings of the National Academies of Science July 21, 2008.

The protein, HMGB1, was previously hypothesized to block DNA repair, senior author Karen Vasquez, Ph.D., associate professor in M. D. Anderson's Department of Carcinogenesis at the Science Park - Research Division in Smithville, Texas.

Identification and repair of DNA damage is the frontline defense against the birth and reproduction of mutant cells that cause cancer and other illnesses.

Pinpointing HMGB1's role in repair raises a fundamental question about drugs under development to block the protein, Vasquez said. The protein also plays a role in inflammation, so it's being targeted in drugs under development for rheumatoid arthritis and sepsis.

"Arthritis therapy involves long-term treatment," Vasquez said. "Our findings suggest that depleting this protein may leave patients more vulnerable to developing cancer."

Long known to attach to sites of damaged DNA, the protein was suspected of preventing repair. "That did not make sense to us, because HMGB1 is a chromosomal protein that's so abundant that it would be hard to imagine cell repair happening at all if that were the case," Vasquez said.

In a series of experiments reported in the paper, Vasquez and first author Sabine Lange, a doctoral candidate in the Graduate School of Biomedical Sciences, tracked the protein's impact on all three steps of DNA restoration: access to damage, repair and repackaging of the original structure, a combination of DNA and histone proteins called chromatin.

First, they knocked out the gene mouse embryonic cells and then exposed cells to two types of DNA-damaging agents. One was UV light, the other a chemotherapy called psoralen that's activated by exposure to darker, low frequency light known as UVA. In both cases, the cells survived at a steeply lower rate after DNA damage than did normal cells.

Next they exposed HMGB1 knockout cells and normal cells to psoralen and assessed the rate of genetic mutation. The knockout cells had a mutation frequency more than double that of normal cells, however, there was no effect on the types of mutation that occurred.

Knock out and normal cells were then exposed to UV light and suffered the same amount of damage. However, those with HMGB1 had two to three times the repair as those without. Evidence suggests that HMGB1 works by summoning other DNA repair factors to the damaged site, Vasquez said.

The last step in DNA repair is called chromatin remodeling. DNA does not exist in a linear structure in the chromosome, but wraps around specialized histone proteins. This chromatin structure permits access to DNA when it is loose, or opened up, and blocks access when it is more tightly wrapped. Presence of HMGB1 resulted in a much higher rate of chromatin assembly in both undamaged and UVC-damaged cells.

Lange and Vasquez hypothesize that HMGB1 normally binds to the entrance and exit of DNA nucleosomes, so is nearby when DNA damage occurs. It then binds to and bends the damaged site at a 90-degree angle, a distortion that may help DNA repair factors recognize and repair the damage. After repair it facilitates restructuring of the chromatin.

Co-author with Lange and Vasquez is David Mitchell, Ph.D., professor of carcinogenesis.

The research was supported by grants from the National Cancer Institute and the National Institute of Environmental Health Sciences as well as an American Legion Auxiliary fellowship.


Story Source:

The above story is based on materials provided by University of Texas M. D. Anderson Cancer Center. Note: Materials may be edited for content and length.


Cite This Page:

University of Texas M. D. Anderson Cancer Center. "Once-suspect Protein Found To Promote DNA Repair, Prevent Cancer." ScienceDaily. ScienceDaily, 23 July 2008. <www.sciencedaily.com/releases/2008/07/080721173743.htm>.
University of Texas M. D. Anderson Cancer Center. (2008, July 23). Once-suspect Protein Found To Promote DNA Repair, Prevent Cancer. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2008/07/080721173743.htm
University of Texas M. D. Anderson Cancer Center. "Once-suspect Protein Found To Promote DNA Repair, Prevent Cancer." ScienceDaily. www.sciencedaily.com/releases/2008/07/080721173743.htm (accessed October 20, 2014).

Share This



More Health & Medicine News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How Nigeria Beat Its Ebola Outbreak

How Nigeria Beat Its Ebola Outbreak

Newsy (Oct. 20, 2014) The World Health Organization has declared Nigeria free of Ebola. Health experts credit a bit of luck and the government's initial response. Video provided by Newsy
Powered by NewsLook.com
Another Study Suggests Viagra Is Good For The Heart

Another Study Suggests Viagra Is Good For The Heart

Newsy (Oct. 20, 2014) An ingredient in erectile-dysfunction medications such as Viagra could improve heart function. Perhaps not surprising, given Viagra's history. Video provided by Newsy
Powered by NewsLook.com
Ebola Worries End for Dozens on U.S. Watch Lists

Ebola Worries End for Dozens on U.S. Watch Lists

Reuters - US Online Video (Oct. 20, 2014) Forty-three people who had contact with Thomas Eric Duncan, the first person diagnosed with Ebola in the U.S., were cleared overnight of twice-daily monitoring after 21 days of showing no symptoms. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Fauci: Ebola Protocols to Focus on Training

Fauci: Ebola Protocols to Focus on Training

AP (Oct. 20, 2014) Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, says he expects revised CDC protocols on Ebola to focus on training, observation and ensuring health care workers are more protected. (Oct. 20) 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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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