New gene-silencing pathway found...( Biologists at Washington University ...)

Biologists at Washington University in St. Louis have made major headway in explaining a mechanism by which plant cells silence potentially harmful genes.

Differential gene expression profoundly influences the way in which organisms grow and develop. For instance, although every cell in the human body has the same genetic information, different subsets of the DNA get activated to make an eye different from a toe. RNA polymerases, the enzymes responsible for making RNA from DNA templates, are key players in determining which genes get switched on and which get left off.

A team led by Craig Pikaard, Ph.D., Washington University professor of biology in Arts & Sciences, has been investigating the role of two plant-specific RNA polymerases since playing a leading role in their discovery in 2005. In a paper published Nov. 14, 2008 in Cell, Pikaard and his colleagues explain how these RNA polymerases work together to use the non-coding region of DNA to prevent destructive, virus-derived genes from being activated.

"There's a lot of interest in harnessing this sort of silencing on purpose to be able to silence the genes that you care about," says Pikaard. Understanding the cellular machinery responsible for gene silencing has major implications for gene therapy, where RNA-centric approaches are showing real promise for control of diseases such as cancer and HIV.

Pikaard and his colleagues' work may have important implications for applied medical research. For instance, gene therapy procedures sometimes use retroviral vectors as a way of introducing a foreign gene to replace a function impaired by disease. Often this foreign gene, called a transgene, restores the missing function for a while and then unexpectedly goes silent. Pikaard explains, "It gets inactivated and it's probably the same sort of RNA-directed silencing mechanism." he explains. " If you could prevent the silencing of the transgene or if you co
'/>"/>