# Scientists expand DNA alphabet from 4 to 8 letters Breakthrough enables synthetic biology to engineer new biological functions - **Source:** [Latest Science News -- ScienceDaily](https://brifing.si/source/0eef8637-6c5b-4e79-8f5b-6c9c6b36cf16) - **Published:** 2026-09-05 - **Original article:** - **On Brifing:** https://brifing.si/s/c362a9f6-e47d-4701-9619-c6a40f9417b0 ## Breaking nature's genetic code limit All known life uses just four DNA letters (A, T, C, G). UC San Diego scientists demonstrated RNA polymerase can accurately read an eight-letter synthetic alphabet. This breakthrough suggests cells' existing machinery can handle expanded genetic information, potentially enabling engineered biological systems with unnatural capabilities. ## Molecular microscopy reveals mechanics Using cryo-electron microscopy with atomic-scale resolution, researchers captured RNA polymerase from E. coli processing synthetic base pairs. The images showed the enzyme uses similar structural signals to recognize both natural and artificial genetic letters, explaining its surprising adaptability to expanded alphabets. ## Hydrogen bonds not always necessary A related PNAS study found RNA polymerase can recognize synthetic base pairs lacking hydrogen bonds - the forces that normally hold DNA together. This unexpected flexibility suggests biological systems may be more adaptable to synthetic components than previously thought. ## From cancer detection to therapeutics Previous research used expanded genetic alphabets to create synthetic DNA that recognizes liver cancer cells. The new detailed understanding of RNA polymerase's capabilities provides a foundation for developing novel diagnostic tools, targeted therapies, and engineered biological systems with customized functions. ## Precision structural insights The high-resolution structural views revealed exactly how RNA polymerase positions itself when reading synthetic letters. These atomic-level details are crucial for designing future synthetic biology applications that rely on expanded genetic codes working within natural cellular machinery. ## Two landmark studies The Nature Communications paper (Sept 2026) detailed eight-letter alphabet transcription, while the PNAS study (Aug 2026) showed hydrogen bonds aren't essential for recognition. Both were led by Dr. Dong Wang at UC San Diego's Skaggs School of Pharmacy, representing years of synthetic biology research. ## Beyond nature's limitations The research moves synthetic biology closer to creating biological systems that produce compounds not found in nature. Potential applications include manufacturing novel materials, developing more effective medicines, and engineering organisms with customized metabolic pathways for industrial or environmental uses. ## Foundational for future bioengineering By demonstrating how natural enzymes can process expanded genetic codes, this work provides the molecular understanding needed to design next-generation biotechnologies. It represents a significant step toward programming living systems with capabilities beyond what evolution has produced over billions of years. ## Sources covering this story - https://www.sciencedaily.com/releases/2026/09/260904000310.htm — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._