Every living thing on Earth builds its genetic code from the same four letters: A, T, C and G. Researchers at UC San Diego have now shown that one of biology’s most essential enzymes can accurately read and process a synthetic DNA alphabet containing eight letters instead of four, a result published in Nature Communications on September 2, 2026, that offers a real molecular explanation for how expanded genetic systems can actually function inside a cell’s existing machinery.

What was actually demonstrated

The study focused on RNA polymerase, the enzyme responsible for reading a strand of DNA and transcribing it into RNA, the essential first step in turning genetic information into anything a cell actually does with it. Using high-resolution cryo-electron microscopy, a technique that lets researchers see molecular structures in near-atomic detail, the team led by Dong Wang, a professor at UC San Diego’s Skaggs School of Pharmacy and Pharmaceutical Sciences, showed exactly how this enzyme recognizes the four additional, synthetic DNA letters using essentially the same biochemical and structural signals it already uses to recognize the four natural ones.

That’s the key finding: it’s not that scientists built a new, separate enzyme to handle the expanded alphabet. A natural, already-existing enzyme, without modification, was shown to accurately transcribe the expanded eight-letter system, sometimes referred to as “Hachimoji” DNA, a name derived from the Japanese for “eight letters.”

Why RNA polymerase’s ordinary behavior is the actual discovery

Building synthetic DNA letters that can physically pair up correctly, the way A pairs with T and C pairs with G in natural DNA, is itself a significant chemistry achievement, and researchers have been working on expanded genetic alphabets for years. But a synthetic genetic system is only useful if a cell’s existing machinery can actually do something with it, read it, copy it, transcribe it into RNA, without requiring an entirely custom-built biological toolkit just to process the new letters.

This study answers that specific, practical question for one of the most important pieces of that machinery. Showing that natural RNA polymerase recognizes synthetic base pairs through the same structural signals it uses for natural ones means an expanded genetic alphabet isn’t just chemically stable on its own, it’s structurally compatible with at least one core piece of the cellular machinery that would need to work with it in any real application.

A second, related finding: base pairs that don’t even need hydrogen bonds

In a related study from the same research group, published in PNAS on August 12, 2026, the researchers reported something even more unusual: RNA polymerase can also recognize a different pair of synthetic bases that hold together without hydrogen bonds at all, the type of chemical bond that ordinarily holds natural DNA’s base pairs together. Instead, this pair relies on hydrophobic interactions, the same general kind of force that makes oil and water separate, to stay paired and get accurately processed by the enzyme regardless.

That finding matters because it shows the enzyme’s recognition system is more flexible than assumed. It isn’t rigidly dependent on the exact hydrogen-bonding pattern natural DNA uses; it can also work with structurally different chemical strategies for holding a base pair together, widening the design space for what future synthetic genetic systems could actually look like.

What an expanded genetic alphabet could eventually be used for

An eight-letter genetic system carries more potential information per unit of DNA than the standard four-letter version, since more distinct letters mean more possible combinations at every position along a strand. Researchers in this field have pointed toward several long-term applications: new kinds of diagnostics that use expanded genetic tags to detect diseases with more specificity, therapeutics built on genetic material engineered to behave differently from natural DNA or RNA inside the body, and engineered biological systems designed for research or industrial purposes that benefit from genetic “letters” natural biology doesn’t already use for anything else, reducing the risk of unwanted interaction with an organism’s existing genome.

What this study does not mean

This research demonstrates that a natural enzyme can transcribe an expanded genetic alphabet accurately at the molecular level. It does not mean a functioning organism running on eight-letter DNA already exists, or that any of the diagnostic or therapeutic applications researchers point toward as long-term possibilities are close to actual products. This is foundational structural biology, explaining a mechanism, not an announcement of a finished technology.

Common myths about synthetic DNA research

Myth: this means scientists have created new, artificial life forms. The study demonstrates that an existing natural enzyme can transcribe synthetic DNA in laboratory conditions. It does not describe a living organism built entirely on an expanded genetic code.

Myth: an eight-letter DNA system could replace natural DNA in humans. Current research in this area is focused on engineered biological systems, diagnostics and research tools, not on modifying or replacing the natural genetic code of existing organisms, including humans.

Myth: this is the first time scientists have made synthetic DNA letters that pair correctly. Building synthetic base pairs that pair up chemically has been an active area of research for years, including earlier work establishing the eight-letter “Hachimoji” system itself. What’s new here specifically is demonstrating that a natural, unmodified enzyme can accurately transcribe that expanded system.

Frequently asked questions

What enzyme did this study focus on, and why does that enzyme matter?
RNA polymerase, the enzyme responsible for reading DNA and transcribing it into RNA, the essential first step in gene expression. Demonstrating it can accurately process an eight-letter genetic alphabet shows that expanded genetic systems are compatible with existing core cellular machinery, not just chemically stable in isolation.

Who led this research, and where was it published?
Dong Wang, a professor at UC San Diego’s Skaggs School of Pharmacy and Pharmaceutical Sciences, led the study, published in Nature Communications on September 2, 2026, with a related study on hydrogen-bond-free synthetic base pairs published in PNAS on August 12, 2026.

What is “Hachimoji” DNA?
Hachimoji, meaning “eight letters” in Japanese, refers to the expanded synthetic genetic alphabet system that adds four additional letters to the four, A, T, C and G, used by all known natural life.

For more on foundational science research and how to evaluate what a study does and doesn’t actually show, see our companion piece Why Most Statistics You See in the News Are More Fragile Than They Look.