Magazine article Science News

Gene Finding Gives Clues to DNA Repair

Magazine article Science News

Gene Finding Gives Clues to DNA Repair

Article excerpt

In the mid-1960s, as a postdoctoral student, James E. Cleaver thought a lot about the genetics of radiation sensitivity in cells. One day, he read a newspaper report about xeroderma pigmentosum (XP), a rare disease that renders people ultrasensitive to sunlight. Are people with XP, Cleaver wondered, somehow unable to repair the genetic damage caused by exposure to the sun's ultraviolet rays?

"It was the kind of [hypothesis] that if I was right, I had a living out of it, and if I was wrong, nobody would have noticed," recalls Cleaver, now a geneticist at the University of California, San Francisco. He proposed the connection between XP and faulty DNA repair and proved it. Now, 25 years after Cleaver's initial report, two teams of scientists have independently flushed out the defective gene that causes a particularly severe form of the disease, XP-G. The researchers report their work in the May 13 NATURE.

Defects in this gene, and in seven others linked to different forms of XP, interfere with normal DNA repair. Usually, these genes serve as a blueprint for enzymes that recognize and cut out sections of cells' damaged DNA. Other cell mechanisms clear away the wreckage and replace the damaged sections of genetic code.

People with XP suffer various symptoms, depending on which defective gene they carry. In people with XP-A, for example, DNA repair is almost completely knocked out, causing brain deterioration and many skin tumors. In contrast, people with less severe forms of the disease can avoid many of its serious symptoms by simply avoiding exposure to sunlight. About one person in 100,000 has the disease, says Richard D. Wood, a biochemist at Clare Hall Laboratories in South Mimms, England.

DNA repair, the researchers emphasize, has proved one of the most fundamental aspects of cell life. …

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