Molecular 'security' checks harmful DNA

The finding could pave the way to improvements in genetic engineering and gene therapy technologies, scientists believe.

Researchers from the University of Minnesota found an enzyme in human immune cells that disables double-stranded foreign DNA by altering one of its chemical elements.

They found that the enzyme, called APOBEC3A, transformed cytosine, one of the four main “bases” in DNA that make up the genetic code, into a rarer form called uracil.

Persisting uracils eventually disable DNA, making unwanted foreign DNA molecules safely inactive.

Other enzymes then step in to degrade the uracil-neutralised DNA and sweep its remains out of the cell.

Foreign DNA can infiltrate the genetic code, or genome, leading to malfunctions and disease.

The study also suggests that as much as 8 per cent of human DNA may originally have been imported from a virus and could play a role in mental illnesses such as schizophrenia.

The research has been published in the online journal Nature Structural and Molecular Biology.