Scientists discover new way to reverse genetic defects

Scientists have discovered a way to bypass the type of mutation that causes about a third of human genetic diseases.

Experiments in yeast have shown how chemical modifications can allow a cell's machinery to ignore mistakes in DNA known as nonsense mutations. These stop the machinery prematurely during protein production, resulting in a shorter-than-usual protein that may function incorrectly or not at all.

For proteins to be produced in the cell, molecules called mRNA translate the information stored within DNA into amino acids, which are the building blocks of proteins. At the end of this mRNA there is normally a stop codon - a three-letter sequence that tells the machinery to cease activity - but problems can arise if this appears in the wrong place.

The researchers, from the University of Rochester Medical Centre in the USA, hope their work will lay the foundations for better treatments of some common diseases.

In an interview with the Guardian, Professor Yitao Yu said: 'Our work is still really early with regard to clinical application. However, we believe it will eventually offer a potential therapeutic option for premature stop codon-caused diseases, such as cystic fibrosis and muscular dystrophy'.

In the study, published in Nature, Professor Yu and first author Dr John Karijolich used yeast with a genetic mutation that prevents it surviving in a copper sulphate solution. However, they also provided it with mRNA that produces a protein that confers resistance to this chemical.

The catch was this mRNA contained a nonsense mutation and wouldn't produce a complete protein until they engineered the cells to produce a chemical to turn this stop sign into a 'go'. This allowed the machinery to continue translating the mRNA sequence into a healthy, full-size protein at nearly the same rate as cells with no genetic flaws.

'This is a very exciting finding', said Professor Yu. 'No one ever imagined that you could alter a stop codon the way we have and allow translation to continue uninterrupted like it was never there in the first place'.

Although this research holds great potential, more work is required to see if it applicable to humans and human diseases, especially as the protein produced may not be exactly the same as the one produced in a cell without the premature stop codon.