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Gene for repairing DNA found in radiation-resistant microbe
By Adam Marcus

Scientists have identified a gene that is essential for the repair of damaged DNA in a microbe. A similar gene has not been found in humans, but the discovery could help researchers understand the important process of how errors in the genome are corrected.

Most healthy cells routinely repair slight DNA errors. Some cancers, including certain breast and colon tumors, are due to faulty DNA repair. And cancer therapies that target tumor cells can also lead to DNA damage in normal tissue.

D. radiodurans

The microbial gene, called irrE, was identified in Deinococcus radiodurans, a bacterium that can withstand a thousand times more radiation than a person can. The gene appears to help regulate the process of mending DNA. Bacteria without the gene were vulnerable to radiation damage.

The discovery was made by Ashlee Earl and her colleagues at Louisiana State University, in Baton Rouge, and presented recently at a meeting in New Orleans of the American Society for Microbiology and the Institute for Genomic Research.

Repair mechanisms are likely to have been conserved throughout evolution, so repair genes in D. radiodurans may be found in other organisms, including humans.

"Even if the actual proteins aren't conserved directly, there may be a similar kind of repair mechanism at work," says Michael Volkert, a molecular geneticist at the University of Massachusetts Medical School in Worcester, who studies DNA repair.

Although organisms can generally patch up breaks in single strands of DNA, D. radiodurans fixes double-stranded breaks with ease. In fact, while E. coli bacteria cannot overcome a single double-stranded break, D. radiodurans can repair 100 and survive, according to James Keck, a molecular biologist at the University of Wisconsin, in Madison.

Earlier this year scientists proposed that D. radiodurans owes its durability to the way its genome is formed in tightly packed rings. Several researchers challenged that conclusion.

See related GNN articles
»Microbe's donut-shaped genome packs a punch
»Discovering DNA repair genes in C. elegans

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Earl, A. et al. The IrrE Protein of Deinococcus radiodurans is a Novel Regulator of recA Expression. 3rd ASM & TIGR Conference on Microbial Genomes. (January 30-February 1) New Orleans, LA)

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