In the last few years scientists have been surprised by small nucleotide sequences, microRNAs and siRNAs (small interfering RNAs), that appear to play a role in both suppressing and promoting cancer. “We are at a transition in our understanding of RNA,” said Phillip A. Sharp, Ph.D., Nobel laureate and Institute Professor at the Massachusetts Institute of Technology. “RNA is taking on a new role. It is a regulatory molecule.”

These small RNAs are double-stranded sequences of about 22 nucleotides that act by disrupting messenger RNA. According to Sharp, they regulate up to a fifth of human genes, a function once thought to be the exclusive province of proteins. “The double strand is the signature key that converts the RNA into a regulatory molecule,” Sharp said in June as he gave the Adelberg Lecture sponsored by the Department of Genetics.

This regulatory role could have therapeutic value if it can be harnessed to turn off mutant, disease-causing genes. “The big problem with using siRNAs is how to introduce them into the cell,” Sharp said. “That delivery problem stands between this being a very broad platform for therapeutics and where we are at now.”