New Mysterious Class of RNA

When first discovered, the ribonucleic acid (RNA) was regarded as just a link in a chain that passed the message encoded in DNA to protein factories: the ribosomes.

But with the advanced genetic research, in the last few years RNA was upgraded.

The findings of RNA interference and microRNAs showed that this molecular type plays a major role in genomic activity. Now, a research team led by David Bartel, a professor in MIT's Department of Biology, has encountered an entirely new class of RNA molecules. More than 5,000 of these new molecules, baptized 21U-RNAs, were discovered in the C. elegans worm.

The name of these new RNAs depicts their qualities: Each molecule contains 21 nucleotide bases (chemical building blocks), and each starts with the basis named uridine, represented "U" (the only RNA nucleotide basis not found on DNA).

All 5,000 different 21U-RNA molecules originated from one of two chromosomal regions. Further, "we can predict where additional 21U-RNA genes might reside," says Bartel, who is also a member of the Whitehead Institute for Biomedical Research and a Howard Hughes Medical Institute investigator. "Combining these predictions with the 5,000 (21U-RNAs) that we experimentally identified, we suspect that there are more than 12,000 different 21U-RNA genes in the genome."

"There are so many 21U-RNA genes spread out over such a wide swath of the genome, but they all share common requirements for expression and common structural features," says Bartel lab Ph.D. student J. Graham Ruby, lead author on the study.

Till now, the function of these molecules remains unknown, but their uniform structure points towards a specific role. This "common structure and origin suggests an important function," said MIT Institute Professor and Nobel Laureate Phillip Sharp, a biologist.

"It requires function to conserve specificity."