Featured Research

from universities, journals, and other organizations

Damaged DNA Synthesis Enzyme Shown To Cause Progressive Muscle Weakening

Date:
May 7, 2002
Source:
NIH/National Institute Of Environmental Health Sciences
Summary:
Researchers at the National Institute of Environmental Health Sciences have filled in a last bit of evidence showing how and why an inherited, degenerative disease generally gets worse with time. The researchers reported in the Journal of Biological Chemistry that they have demonstrated in the laboratory for the first time that in the replication of a subset of genes (the mitochondrial genes) a damaged enzyme makes errors ten-fold to 100-fold more frequently than in healthy individuals.

Researchers at the National Institute of Environmental Health Sciences have filled in a last bit of evidence showing how and why an inherited, degenerative disease generally gets worse with time. The researchers reported in the Journal of Biological Chemistry that they have demonstrated in the laboratory for the first time that in the replication of a subset of genes (the mitochondrial genes) a damaged enzyme makes errors ten-fold to 100-fold more frequently than in healthy individuals.

The researchers compared what happens to a typewriter with a slightly damaged key: "This enzyme frequently makes mistakes while copying the mitochondrial genes, and the accumulation of the mistakes causes the muscle weakness to progress," according to one of the researchers.

This is the first time that such a damaged enzyme -- a DNA synthesis enzyme -- has been shown to play a role in a degenerative disease, in this case a condition called progressive external ophthalmoplegia.

The scientists said that their work applies specifically to this rare affliction in which the eye muscles deteriorate and the patient must move his head, rather than his eyes, to follow an object. However, they said, the principle of repeated, copying errors applies to other mitochondrial degenerative conditions as well, including aging itself.

The answer to the riddle of why degenerative diseases progress with time, the involved muscles getting progressively weaker, has been long in coming:

Nearly 40 years ago, a patient with such a disease was found to have abnormal mitochondria, the main energy-producing component of the cells in the body. Mitochondria play an important role in the proper functioning of energy-hungry organs like the eyes, kidneys and heart and brain.

They act semi-independently from the rest of the cell, and they contain a set of 37 specialized genes on a tiny chromosome. Mutations in any of the mitochondrial genes can cause a cellular energy deficit, the first symptoms of which is often the muscular degeneration known as progressive external ophthalmoplegia.

Recently, this disease was linked to a mutation (called Y955C) in one of the cell's genes that produces the enzyme (DNA polymerase gamma) that is responsible for replicating mitochondrial DNA.

In their report, the NIEHS researchers describe the first laboratory evidence that this faulty enzyme causes the ophthalmoplegia, or paralysis of the eye, by causing changes in the mitochondrial genes. The scientists said that this is also the first time that such a damaged enzyme has been shown to play a role in a degenerative disease.

Reporting the work are Mikhail V. Ponamarev, Ph. D., Matthew J. Longley, Ph.D., Dinh Nguyen, Thomas A. Kunkel, Ph.D., and William C. Copeland, Ph.D. Dr. Kunkel leads the DNA Replication Fidelity Section at NIEHS while Dr. Copeland leads the Mitochondrial Replication Section in the Laboratory of Molecular Genetics. Dr. Copeland's group was the first to clone the DNA that encodes polymerase gamma in 1996.


Story Source:

The above story is based on materials provided by NIH/National Institute Of Environmental Health Sciences. Note: Materials may be edited for content and length.


Cite This Page:

NIH/National Institute Of Environmental Health Sciences. "Damaged DNA Synthesis Enzyme Shown To Cause Progressive Muscle Weakening." ScienceDaily. ScienceDaily, 7 May 2002. <www.sciencedaily.com/releases/2002/05/020507073606.htm>.
NIH/National Institute Of Environmental Health Sciences. (2002, May 7). Damaged DNA Synthesis Enzyme Shown To Cause Progressive Muscle Weakening. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2002/05/020507073606.htm
NIH/National Institute Of Environmental Health Sciences. "Damaged DNA Synthesis Enzyme Shown To Cause Progressive Muscle Weakening." ScienceDaily. www.sciencedaily.com/releases/2002/05/020507073606.htm (accessed July 28, 2014).

Share This




More Health & Medicine News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
West Africa Gripped by Deadly Ebola Outbreak

West Africa Gripped by Deadly Ebola Outbreak

AFP (July 28, 2014) The worst-ever outbreak of the deadly Ebola epidemic grips west Africa, killing hundreds. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com
Google's Next Frontier: The Human Body

Google's Next Frontier: The Human Body

Newsy (July 27, 2014) Google is collecting genetic and molecular information to paint a picture of the perfectly healthy human. Video provided by Newsy
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