The RNA silencing machinery silences gene expression, by destroying RNA, a molecule that carries out DNA's instructions. Two years ago, components of the RNA silencing machinery were shown to be absolutely required for forming heterochromatin, a chromatin state that silences DNA, suggesting a new rule in biology. But researchers from Texas A&M University and the University of Oregon disagree.

They broke that rule in reporting their findings in the July 25 issue of Science magazine. Funding for the research is supported by grants from the National Institutes of Health.

Knowledge gained from their research will enable scientists to better understand the complexities of chromosome biology, which ultimately will lead to conquering disease by the means of gene therapy, says Rodolfo Aramayo, associate professor of biology at Texas A&M University, who specializes in genetics and studies the biology of meiotic chromosomes. Since the majority of birth defects are caused by chromosomal abnormalities, he says it is absolutely fundamental to understand how chromosomes work.

"Understanding normal chromosome biology is more than a curious scientific endeavor," says Aramayo. "It is a must if we ever are to conquer disease."

In a study with Neurospora crassa, a mold, Aramayo and his colleagues created mutant cells that cannot produce any key components of the RNA silencing mechanism, and discovered that heterochromatin formed just fine.

"Think about a chromosome as being a highway," says Aramayo. "In order to function properly, some sections of the highway must have illumination, which means DNA must be
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27-Jul-2004