Synthetic genetic alphabet with eight letters successfully read by RNA polymerase

UC San Diego researchers demonstrated that RNA polymerase can accurately read an eight-letter genetic alphabet, doubling the four letters used by all known life. This synthetic genetic expansion could enable new possibilities in biotechnology. The work was published recently.

All known organisms encode genetic information using just four nucleotide letters, which combine to form genes and direct protein production. The UC San Diego team's work shows that a synthetic system with eight letters can still be processed by RNA polymerase, the enzyme responsible for transcribing DNA into RNA. This suggests that expanded genetic alphabets are not merely stable in storage but can participate in the fundamental copying step of gene expression.

The demonstration represents a milestone in synthetic biology, a field that seeks to redesign biological systems for novel functions. By proving that the cellular machinery tolerates additional letters, researchers open a path toward storing more information per gene and creating proteins with unnatural amino acids. The findings were published recently, adding to a growing body of work on xenobiology and expanded genetic codes.