Plate Nº 42 · recorded October 10, 2026
Biology & EvolutionReported finding
Eight-Letter DNA Works: Scientists Show Cells Can Read a Doubled Genetic Alphabet
UC San Diego researchers showed RNA polymerase can accurately read an eight-letter DNA alphabet, revealing how cells might handle synthetic genetic codes.
By Elena Vasquez3 min read620 words
In brief
- A Nature Communications study published Sept. 2, 2026 shows E. coli RNA polymerase accurately reads an eight-letter genetic alphabet.
- Cryo-electron microscopy resolved structures at scales smaller than the width of a single atom.
- A related PNAS study published Aug. 12, 2026 showed recognition of base pairs lacking hydrogen bonds.
- Both studies were led by Dong Wang of UC San Diego's Skaggs School of Pharmacy.
- Earlier work already used expanded alphabets to make DNA that recognizes liver cancer cells.
Every living thing on Earth reads its genes with four chemical letters. On September 2, 2026, researchers at the University of California San Diego showed that a core cellular enzyme can accurately read double that number — an eight-letter genetic alphabet built partly from synthetic DNA letters that do not exist in nature.
The enzyme at the center of the work is RNA polymerase, the molecular machine that reads DNA and produces RNA — the essential first step in turning genes into action. The finding suggests that cells can use their existing molecular machinery to handle synthetic genetic information, a step toward a long-standing goal in synthetic biology: expanding DNA's language beyond the four natural letters A, T, G and C.
The study, led by Dong Wang, PhD, professor at the UC San Diego Skaggs School of Pharmacy and Pharmaceutical Sciences, appeared in Nature Communications under the title "Structural Basis of Transcription of the Hachimoji Eight-Letter Alphabet by E. coli RNA Polymerase."
How did the researchers watch an enzyme read alien DNA?
The team combined biochemical experiments with high-resolution cryo-electron microscopy, an imaging technique so precise it can reveal structures at scales smaller than the width of a single atom. Cryo-electron microscopy works by flash-freezing molecules and imaging them with electron beams, producing detailed three-dimensional views of biological machines at work.
Using this approach, the researchers captured structural snapshots of RNA polymerase from Escherichia coli bacteria as it recognized and incorporated two synthetic base pairs — artificial genetic letters found nowhere in nature.
The images answered a basic question: how does an enzyme shaped by billions of years of four-letter evolution cope with unfamiliar chemistry? The answer turned out to be surprisingly simple. RNA polymerase identifies the synthetic DNA letters using many of the same biochemical and structural signals it relies on to recognize natural base pairs. That overlap helps explain why the enzyme can copy information written in an expanded alphabet with reasonable accuracy.
A second, related study from the same team pushed the point further. Published in PNAS on August 12, 2026, it showed that RNA polymerase can recognize yet another pair of synthetic bases even though those pairs lack the hydrogen bonds — the weak chemical attractions that normally help hold DNA base pairs together.
What does this mean for synthetic biology?
The potential applications extend well beyond understanding how DNA works. Earlier research has already used expanded genetic alphabets to create synthetic DNA molecules capable of recognizing liver cancer cells.
By showing in molecular detail how RNA polymerase reads and transcribes non-natural letters, the new studies lay a foundation for technologies built around expanded genetic codes. Possible applications the researchers point to include:
- new diagnostic tools;
- therapeutics;
- engineered biological systems with capabilities that do not occur in nature.
In such systems, cells might one day produce compounds that no natural organism makes, or carry out functions designed from scratch.
How solid are the findings — and what are the limits?
The structural results are preliminary in scope. They demonstrate accurate reading of specific synthetic base pairs by a bacterial enzyme under controlled laboratory conditions, not a fully functioning organism running on eight-letter genetics. Extending the results to living cells that stably store and use expanded alphabets remains an unsolved engineering challenge.
Still, the two papers mark a concrete advance: they explain, at the level of atoms and molecular shape, why nature's own transcription machinery tolerates unnatural DNA. That mechanistic knowledge is exactly what engineers need to design synthetic letters that cells can reliably copy.
The research was a collaboration involving scientists including Qingrong Li, Steven A. Benner, Dmitry Lyumkis and others across UC San Diego and partner institutions.
via dx.doi.org (Original)
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