Scientists Find 2-Template Bacterial DNA System That Builds C-A-C-A Strands Against Viruses
Updated
Updated · ScienceAlert · Aug 23
Scientists Find 2-Template Bacterial DNA System That Builds C-A-C-A Strands Against Viruses
2 articles · Updated · ScienceAlert · Aug 23
Summary
Researchers found an E. coli defense system, DRT3, that makes one DNA strand from a protein template rather than from DNA or RNA, producing a repeating C-A-C-A-C-A sequence.
Cryo-EM and mutation experiments showed two amino acids in the DRT3b enzyme direct which DNA bases are added; changing them disrupted both DNA synthesis and antiviral protection.
A second enzyme, DRT3a, separately builds the complementary strand from an RNA template, so the double helix forms only after two independently synthesized strands pair up.
RecBCD normally destroys the unusual DNA, but viruses that disable RecBCD remove that brake, letting DRT3 DNA accumulate and halt bacterial growth to block viral replication.
The Cell study points to an unexpected flow of biological information—from protein to DNA—and suggests bacterial immune systems may contain more unconventional DNA-writing enzymes.
If proteins can write DNA from scratch, could this bizarre bacterial defense system unlock a new era of genetic engineering?
How many more hidden molecular codes exist in nature that completely defy the traditional rules of DNA replication?
DRT3 and the Central Dogma: The 2026 Discovery of Template-Free DNA Synthesis and Its Implications for Biology and Biotechnology
Overview
In April 2026, Stanford scientists discovered the DRT3 system in E. coli, revealing a new way for bacteria to make DNA. Unlike normal enzymes that copy a template, Drt3b uses its own protein shape to guide the creation of repetitive DNA, which helps defend against viruses. When a virus attacks, it introduces a protein that activates DRT3, leading to the buildup of special DNA and triggering the infected cell to self-destruct, protecting the bacterial community. This discovery challenges textbook biology, shows how bacteria evolve defenses, and opens new possibilities and challenges for synthetic biology and medicine.