Scientists have shown how the hepatitis C virus uses a small RNA molecule in the liver to ensure its own survival.
MiR-122 is a prominent micro RNA in liver cells that regulates gene expression. When this is bound with the viral RNA, the latter is stabilised, allowing the liver to boost its chances of survival.
The finding is expected to help researchers understand why a new antiviral drug is appearing effective against hepatitis C.
In 2005, it was discovered that miR-122 is required for hepatitis C to replicate itself, although how it did this was unknown.
Stanley M. Lemon, MD, professor of medicine and microbiology and immunology and a member of UNC Lineberger Comprehensive Cancer Center and the Center for Translational Immunology, said the virus does "two very interesting things to RNA".
"First, it has evolved a unique relationship with a key regulator, since miR-122 represents about half of all microRNAs present in the liver.
"Second, the virus has usurped a process that usually downregulates gene expression to upregulate the stability of its RNA and expression of viral proteins needed for its lifecycle. It's a classic example of how viruses subvert normally beneficial functions of the cell to their own nefarious purposes," he explained.
The new drug proving effective against the virus is known as an antagomer. The drug binds to miR-122 and sequesters it in the liver, destabilising the viral genome and quickening its degradation in the liver.
Hepatitis C presents such a large public health challenge as symptoms usually do not appear until months or years after the initial infection, with many of those with the disease not knowing they are infected.
Last year, scientists discovered a compound, known as PD 404,182, which essentially dissolves viruses and works on hepatitis C, as well as lentiviruses, and could possibly be used to develop a new topical preventative for HIV.
"Since RNA is pretty unstable, once it is exposed it's gone very quickly and the virus is rendered non-infectious," Zhilei Chen, assistant professor in Texas A&M's Artie McFerrin Department of Chemical Engineering, explained.