When viruses attack, some bacteria reach for a molecular tool that looks strikingly familiar to anyone who studies human cells. Scientists at Columbia University report in Nature that a newly characterised defence system called DRT10 builds DNA in much the same way as telomerase, the enzyme that stops the tips of our chromosomes from wearing down.
The find emerged from a family of bacterial reverse transcriptases so poorly understood that researchers dubbed it the “Unknown Group” in 2008. Graduate student Stephen Tang, working in biochemist Samuel Sternberg’s laboratory, showed that one of its members shields its host from infection by churning out long runs of repetitive DNA, copied again and again from a short RNA template.
That copy-and-repeat routine is precisely how telomerase restores telomeres in yeast, plants, animals and people. The resemblance might have remained a footnote had Copenhagen collaborator Mario Rodríguez Mestre not shown the team a family tree of all known reverse transcriptases. Sternberg noticed a thin cluster of enzymes from complex organisms sitting snugly among the bacterial ones; that cluster was telomerase. Further analyses point to a common ancestor, implying that repeat-building chemistry predates cells with nuclei and was later put to work capping their linear chromosomes.
The discovery also adds a new kind of instrument to the gene-engineering kit. CRISPR cuts, base editors swap single letters, but DRT10 writes fresh sequence from RNA. The group has already used it to make human telomere repeats inside human cells and now wants to learn whether lengthening chromosome ends can delay cellular ageing.
Possible targets include inherited telomere disorders and CAR-T cancer therapy, where engineered immune cells that stay active longer could help patients. Sternberg calls it “early days”. The university is seeking patent protection for the system.
