When the scientists inactivated the microRNA, the amount of hepatitis C virus RNA was reduced by approximately 80 percent. The discovery was widely heralded for its potential to develop new antiviral agents against hepatitis C, the most common blood-borne viral infection in the United States, affecting more than 2.5 million Americans and a staggering 170 million people worldwide. The best treatment regimens now available are difficult, expensive, laden with serious side effects and effective in only half the cases.
Dr. Sarnow discusses the most recent findings in this work on April 5 at Experimental Biology 2006 in San Francisco. His presentation is part of the scientific program of the American Society for Biochemistry and Molecular Biology.
MicroRNAs, or miRNAs for short, are small RNA molecules that regulate genes in many plant and animal species. Although miRNAs were not discovered until the mid-1990, a growing number of studies suggest that over 300 human genes encode microRNAs and that these microRNAs may control gene expression for as much as a third of the human genome, acting as key regulators of processes as diverse as early development, cell proliferation and cell death, and cell differentiation. Some miRNAs are located throughout the body, while others are found only in specific tissue. The miRNA whose surprising new role was discovered by Dr. Sarnow and his colleagues is located only in the liver. The Sarnow team found that miR-122 binds to a specific noncoding binding region in virus, called target 5' NCR. This is the first example of an animal RNA that interacts with its target 5' NCR, and opens an interesting possibility that other viral 5' NCRs are similarly targeted by different miRNAs.