Four new DNA letters double life’s alphabet

The DNA of life on Earth naturally stores its information in just four key chemicals — guanine, cytosine, adenine and thymine, commonly referred to as G, C, A and T, respectively.

Now scientists have doubled this number of life’s building blocks, creating for the first time a synthetic, eight-letter genetic language that seems to store and transcribe information just like natural DNA.

In a study published on 22 February in Science1, a consortium of researchers led by Steven Benner, founder of the Foundation for Applied Molecular Evolution in Alachua, Florida, suggests that an expanded genetic alphabet could, in theory, also support life.

“It’s a real landmark,” says Floyd Romesberg, a chemical biologist at the Scripps Research Institute in La Jolla, California. The study implies that there is nothing particularly “magic” or special about those four chemicals that evolved on Earth, says Romesberg. “That’s a conceptual breakthrough,” he adds.

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Still, Benner says that the work shows that life could potentially be supported by DNA bases with different structures from the four that we know, which could be relevant in the search for signatures of life elsewhere in the Universe.

Adding letters to DNA could also have more down-to-earth applications.

With more diversity in the genetic building blocks, scientists could potentially create RNA or DNA sequences that can do things better than the standard four letters, including functions beyond genetic storage.

For example, Benner’s group previously showed that strands of DNA that included Z and P were better at binding to cancer cells than sequences with just the standard four bases3. And Benner has set up a company which commercialises synthetic DNA for use in medical diagnostics.

The researchers could potentially use their synthetic DNA to create novel proteins as well as RNA. Benner’s team has also developed further pairs of new bases, opening up the possibility of creating DNA structures that contain 10 or even 12 letters. But the fact that the researchers have already expanded the genetic alphabet to eight is in itself remarkable, says Romesberg. “It’s already doubling what nature has.”

Source: Four new DNA letters double life’s alphabet