in its potential as was Johannes Gutenberg's printing press.And likeGutenberg's invention, most DNA editing tools are slow, expensive, and hard to
use a brilliant technology in its infancy.professor at the Media Lab at the Ma*sachusetts Institute of Technology."You
have to change it functionally and radically."
Such change, Church said, serves three goals.The first is to add functionality
to a cell by encoding for useful new amino acids.The second is to introduce
safeguards that prevent cross-contamination between modified organisms and the
wild.A third, related aim, is to establish multiviral resistance by rewriting
code hijacked by viruses.such viruses affect up to 20 percent of cultures.A notable example afflicted
the biotech company Genzyme, where estimates of losses due to viral
contamination range from a few hundred million dollars to more than $1 billion.
In a paper scheduled for publication July 15 in Science, the researchers
describe how they replaced instances of a codon a DNA "word" of three
nucleotide letters in 32 strains of E.coli, and then coaxed those partially
edited strains along an evolutionary path toward a single cell line in which all
314 instances of the codon had been replaced.
That many edits surpa*ses current methods by two orders of magnitude, said
Harris Wang, a research fellow in Church's lab at the Wyss Institute for
Biologically Inspired Engineering who shares lead-author credit on the paper
with Farren Isaacs, an a*sistant professor of molecular, cellular, and
developmental biology at Yale University and a former Harvard research fellow,
and Peter Carr, a research scientist at the MIT Media Lab.
In the genetic code, most codons specify an amino acid, a protein building
block.But a few codons tell the cell when to stop adding amino acids to a
protein chain, and it was one of these "stop" codons that the Harvard
researchers targeted.With just 314 occurrences, the TAG stop codon is the
rarest word in the E.coli genome, making it a prime target for replacement.
Using a platform called multiplex automated genome engineering, or MAGE, the
team replaced instances of the TAG codon with another stop codon, TAA, in living
E.coli cells.
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