Eight-letter DNA alphabet read by bacterial RNA polymerase in the lab

UC San Diego researchers demonstrated that bacterial RNA polymerase can transcribe an eight-letter genetic alphabet (four natural nucleotides plus four synthetic ones) into RNA. Cryo-EM structures show the synthetic bases fit in with a Watson–Crick geometry, but fidelity suffers from the Z nucleotide, which a Z* variant helps mitigate. This achievement reflects transcription in controlled biochemical systems—not a fully eight-letter organism—with potential future applications in diagnostics, molecular tools, and expanded genetic information, though translation to proteins remains to be shown.