Wednesday, April 25, 2012

Junk DNA can function as virus detector

DNA is the blueprint for the information that all life forms depend on. Cells use specialized machinery to read specific parts of the genetic code, called genes, which are used for the production of proteins. In turn, proteins govern almost all cellular functions and thus are the building blocks of life. Despite the fact that our entire genetic code, dubbed the genome, holds tens of thousands of genes, there are large parts that are not used for protein production at all. This so-called junk DNA was thought to be unimportant, as remnants of evolutionary processes. More recently it was revealed junk DNA does have surprising functions, such as distinguishing us from monkeys. A recent study shows this so-called non-coding DNA is able to function as a detector for virus infections. This is normally a job for the immune system, which is why the role of our DNA is peculiar.

To get the information from the DNA to protein-producing facilities in the cell, an intermediate is needed, called RNA. By reading genes, a mirror image of the genetic information is created, which is small enough to move throughout the cell and get it to the place where it is needed. Junk DNA creates RNA molecules that do not translate into proteins, which is why scientists have long thought that they are useless. More recently, it was shown that RNA can do more than just function as a simple messenger.
From DNA to protein: transcription and translation, with the aid of RNA.
At the Tel Aviv University, scientists discovered that some RNA molecules that do not code for a protein product can give out signals to indicate viral presence. So-called ncRNA molecules do this by multiplying during infection, but their exact role is still unclear. Still, it is likely that a response holds biological relevance, and deserves further investigation.

Experiments showed that some viruses can cause an increase in ncRNA, that surprisingly can be detected with 100 percent accuracy, which shows it is a strong indicator for infection. As said, the specific role of these ncRNA molecules is unclear, but it could be that they are recruited by the virus, to help destroy the host cell. Therefore, inhibiting their production could be a potential anti-viral treatment.

It was already known that viruses target genetic code and the corresponding cellular machinery to alter the read-out of genes. This is necessary to get the cell to produce viral substances, that are consequently assembled into new viruses. Because they have no means of replicating themselves, viruses rely on inserting their genetic code into ours, and thereafter hijack cellular machinery to gather information from the viral genes to build viral proteins. Its effect on non-coding pieces of the genome is something new, but it is likely to be important for the virus to make it spread throughout the body.

As said, more research is needed to uncover the exact role of ncRNA, but it is peculiar that our genetic code plays its own role in detecting a virus infection. Normally, the cell has specialized receptors to detect the presence of invaders, which are used by the immune system to clear away the infection. It seems that ncRNA is a whole new concept in the immunology of virus infection. 


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