Credit: Eduardo de Ugarte, Berkeley Lab Creative Services

Ordering synthetic oligos or genes online is now commonplace and an essential resource to scientists across disciplines. But the phosphoramidite chemistry currently used to synthesize DNA is limited to direct synthesis of about 200 nucleotides, with longer stretches requiring assembly. The capacity to synthesize long stretches of DNA is important for a variety of applications, including DNA storage, DNA origami, and to synthesize DNA containing regions with repeats, which are difficult to put together. In a paper published recently in Nature Biotechnology, Jay Keasling and colleagues report a promising new approach to DNA synthesis. Using a terminal deoxynucleotidyl transferase (TdT) conjugated to a single deoxyribonucleoside triphosphate (dNTP), they tether the primer to TdT after extending it by one nucleotide. This tethering prevents further extension until the dNTP is cleaved by, for example, light. Keasling and colleagues demonstrate synthesis of short oligos, providing proof-of-principle for a method that may in time represent a useful approach to enzymatic DNA synthesis.

Irene Jarchum