Scientists create protein-based bacterial DNA
- A Stanford team reported in Science on April 16 that a bacterial anti-phage system called DRT3 can build defined DNA partly from a protein template, not only from nucleic acids. - The paper says DRT3 makes alternating poly(GT/AC) double-stranded DNA; one enzyme copies an RNA ACACAC motif, while its partner adds the matching poly(AC) strand without a nucleic acid template. - The finding extends a fast-growing list of unusual bacterial reverse-transcriptase defenses, including DRT2, DRT9 and a new DRT7 preprint. (science.org)
Cells usually build DNA by copying an existing DNA or RNA sequence. A Science paper published April 16 reports a bacterial anti-phage system that makes part of its DNA product from a protein-guided template instead. (science.org) The system is called DRT3, short for defense-associated reverse transcriptase 3. It was described by Pujuan Deng, Hyunbin Lee, Carlo Armijo, Haoqing Wang and Alex Gao at Stanford University. (science.org) (gaolab.bio) Phages are viruses that infect bacteria, and bacteria carry many built-in defense systems against them. DRT proteins are one of those defenses, and they have emerged only recently as a large family of anti-phage enzymes with unusual DNA-making chemistry. (nature.com) (science.org) In the DRT3 system, one enzyme called Drt3a reads a short RNA motif — ACACAC — and uses it to build a poly(GT) DNA strand. A second enzyme, Drt3b, then builds the complementary poly(AC) strand. (science.org) The unusual part is that Drt3b does that second step “in the complete absence of a nucleic acid template,” according to the paper. The authors say conserved residues in Drt3b enforce the exact A-C alternation, producing sequence-specific DNA through a protein-templated mechanism. (science.org) The team also reports a cryo-electron microscopy structure at 2.6 angstrom resolution. It shows a D3-symmetric 6:6:6 complex made of Drt3a, Drt3b and a noncoding RNA. (science.org) This is not the first sign that bacterial reverse transcriptases do more than make ordinary complementary DNA. A 2024 Science paper found that DRT2 can generate long DNA products that act as de novo genes during phage infection. (science.org) Another 2025 Science study from Ning Jia’s group reported that DRT9 makes long poly-A-rich single-stranded DNA after phage infection, likely by responding to rising intracellular deoxyadenosine triphosphate, or dATP. (science.org) A bioRxiv preprint posted April 18, 2026 from the same group describes DRT7 as making long, protein-primed, protein-templated poly(A)/poly(T)-rich duplex-like DNA after activation by a phage protein. That study has not been peer reviewed. (biorxiv.org) Taken together, the recent DRT papers describe bacterial antiviral systems that do not fit the standard textbook split between template-directed copying and mostly random template-free nucleotide addition. The DRT3 paper is the peer-reviewed result at the center of the current social-media claims. (science.org) (biorxiv.org)
