Small world produces big results

January 12, 2006, vol. 35, no. 1
By Jennifer Gardy

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Almost everyone knows the Disney ditty It's a Small World. Thanks to the work of scientists like molecular biology and biochemistry assistant professor Peter Unrau we might soon be singing a different tune - it's a small RNA world after all.

Until recently, the biological role of RNA, or ribonucleic acid, was largely underestimated, with most textbooks describing RNA simply as the intermediary that allows DNA to be copied into protein. As Unrau notes, however, “discoveries over the past five to seven years suggest that RNA plays a very important role in what previously was thought to be a protein dominated world.”

One of the most interesting types of RNA identified recently is the small RNA, or smRNA. In a process called gene silencing, smRNAs are able to control not only the amount of protein produced from a gene, but also where and when the protein is made.

“This regulation uses short pieces of RNA to target the actions of particular cellular processes with exquisite accuracy,” explains Unrau. Such fine control over a gene is critical to many activities in the cell, including development and defence against viruses.

In a recent paper in the prominent journal Proceedings of the National Academy of Sciences, Unrau's group, working together with Australian plant biologist Ming-Bo Wang, showed that silencing-associated plant smRNAs are quite different from animal smRNAs. Using tobacco plants, the researchers discovered that plant smRNAS carry a unique chemical modification at their end.

“The results help to explain the differences that have been observed for some time between plant and animal RNA silencing,” says Unrau.

The team is currently working on a paper describing the modified small RNAs in greater detail, including their hypothesis as to the origin of the modification in plants.

“We hope that through this work we may ultimately be able to trace the evolution of this highly important form of gene regulation,” says Unrau. “We understand so little about the biochemistry of this process in plants and animals.”

Ongoing work in Unrau's lab is also focused on understanding RNA's role in the origins of life.

“A number of clues suggest that RNA and not protein was once the dominant biological catalyst,” he says. If this RNA world hypothesis is true, RNA must necessarily be a versatile molecule, capable of carrying out all of the metabolic functions necessary to sustain the earliest life forms.

“Our findings do suggest the chemical dexterity of RNA,” Unrau notes.

What is certain, however, is that Unrau's continued exploration of the RNA world will shed even more light onto this marvelous multi-tasker of a molecule.

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