Wednesday, 22 August 2018

Ancient virus defends koalas against new viral attacks



Date:  August 6, 2018
Source:  University of Illinois College of Agricultural, Consumer and Environmental Sciences

Summary:
A new study in koalas uncovers how virulent retroviruses become harmless bits of 'junk DNA' over time.

The human genome is riddled with endogenous retroviruses -- little pieces of degraded and generally harmless retrovirus DNA passed down through the generations, along with our own genetic information. Because most endogenous retroviruses have been part of our DNA for millions of years, scientists can't explain how they went from their virulent, disease-causing forms to the inert bits of "junk DNA" most of them are today. A new study published today in the Proceedings of the National Academy of Sciences looks to koalas for an answer.

"In humans, the youngest known endogenous retrovirus groups are around 5 million years old. That makes it very hard to tell what happened. But the koala is one of the few species known to have an ongoing invasion of the germline by a retrovirus," says Alfred Roca, one of the authors of the study and an associate professor in the Department of Animal Sciences at the University of Illinois.

Like other viruses, retroviruses first attack from the outside. They enter the body, fuse with cells to release their contents, and insert pieces of their DNA into the genetic code of the host, hijacking the host's DNA-replicating machinery to make more copies of themselves.


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