THE genetic equivalent of a tailor who uses molecular "fingers" to grab onto DNA, before snipping it apart and stitching in a new sequence could lead to safer gene therapies.
In principle, genetic engineering is simple, but inserting a new gene into the right place in an organism's genome is fraught with difficulty. For example, in a gene therapy trial for X-SCID - or "bubble-boy" disease - inserting a gene in the wrong place triggered cancer in some of the recipients.
One approach for locating and snipping DNA strands involves "zinc fingers" - proteins that bind to DNA and can be linked together to recognise extended stretches of DNA with very high specificity. Zinc fingers are usually attached to enzymes called nucleases, dubbed ZFNs, which cut both strands of DNA.
However, the problem with this approach is that it relies on enzymes, the cell's natural repair machinery to ...