Faulty DNA copying may lead to cancer: study

Washington, May 6:

Scientists have found that fragile sites that can be a breeding ground for human cancers appear in specific areas of the genome where the DNA-copying machinery is slowed or stalled.

Each time a human cell divides, it must first make a copy of its 46 chromosomes to serve as an instruction manual for the new cell. Normally, this process goes off without a hitch.

But from time to time, the information isnt copied and collated properly, leaving gaps or breaks that the cell has to carefully combine back together.

Researchers have long recognised that some regions of the chromosome, called fragile sites, are more prone to breakage and can be a breeding ground for human cancers. But they have struggled to understand why these weak spots in the genetic code occur in the first place.

A comprehensive mapping of the fragile sites in yeast by a team of researchers from Duke University showed that fragile sites appear in specific areas of the genome where the DNA-copying machinery is slowed or stalled, either by certain sequences of DNA or by structural elements.

The study, which appears in Proceedings of the National Academy of Sciences, could give insight into the origins of many of the genetic abnormalities seen in solid tumours.

Other studies have been limited to looking at fragile sites on specific genes or chromosomes, said Thomas D Petes, the Minnie Geller professor of molecular genetics and microbiology at Duke University School of Medicine.

Ours is the first to examine thousands of these sites across the entire genome and ask what they might have in common, Petes said.

The term fragile sites was first coined in the 1980s to describe the chromosome breaks that appeared whenever a molecule called DNA polymerase responsible for copying DNA was blocked in mammalian cells.

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Faulty DNA copying may lead to cancer: study