A newly discovered bacterial defense system has opened an unexpected window onto one of the deepest questions in molecular biology: how life on Earth came to protect the ends of its chromosomes. Researchers at Columbia University Irving Medical Center report in Nature that a bacterial antiviral mechanism known as DRT10, short for Defense-Associated Reverse Transcriptase 10, shares a likely common evolutionary origin with telomerase, the enzyme that nearly all higher organisms depend on to maintain their linear chromosomes. The finding, published on October 12, 2026, connects two fields that have long operated in isolation, the study of microbial immunity and the biology of aging and cancer, and suggests that the molecular machinery for writing repetitive DNA may have arisen once, in a common ancestor, long before eukaryotes put it to work safeguarding their genomes.

DRT10 belongs to a growing catalog of bacterial defense systems that rival CRISPR in their ingenuity, but it departs from the familiar playbook in a fundamental way. CRISPR-based defenses and the genome editors derived from them work primarily by cutting DNA at specified sites. DRT10 instead deploys a reverse transcriptase, an enzyme capable of synthesizing DNA from an RNA template, to produce a long strand of DNA bearing a repetitive sequence. That capacity to write new DNA sequences rather than merely sever existing ones is precisely what makes the system so intriguing to biotechnologists. Samuel Sternberg, professor of biochemistry and molecular biophysics at Columbia University Vagelos College of Physicians and Surgeons and a Howard Hughes Medical Institute investigator, who led the study, describes it as an exotic departure from the typical way scientists think about genome engineering. Rather than cutting DNA like CRISPR or swapping single letters of the genetic code like base editors, the system uses RNA as a template to write new sequences of DNA, offering a different starting point for building tools to engineer cells.

The road to the discovery began with a longstanding mystery in bacterial genomics. In 2008, researchers grouped together a collection of bacterial DNA-writing enzymes under the informal label of the Unknown Group, a family of dozens of reverse transcriptases whose functions had never been determined. Because reverse transcription creates new DNA from strands of RNA, these enzymes have long been considered promising raw material for developing genetic tools that could write therapeutic sequences into genomes. Sternberg’s laboratory, which has built its reputation by mining the genomes of bacteria and archaea for inventive ways these organisms control and alter their own DNA, found the family irresistible. As Sternberg notes, the team had a large family of enzymes that could write DNA but almost no idea what bacteria were using them for, a biological mystery with the potential to yield entirely new biotechnology.

It was Stephen Tang, a graduate student in the Sternberg lab, who cracked the case. Searching within the Unknown Group, Tang identified DRT10 and demonstrated that the system fights viral infection by using its reverse transcriptase to generate a long piece of DNA with a repetitive sequence read from a template RNA. Tang worked alongside co-first authors Josephine L. Ramirez and Qixiang He and an international team of collaborators. Ramirez led the biochemical studies that characterized the system’s activity, while He and Israel S. Fernández directed structural work that revealed how DRT10’s protein and RNA components fit together at the molecular level. Together, these complementary approaches provided a first mechanistic portrait of a defense strategy that no one had previously described.

The pivotal realization came as Tang probed how the reverse transcriptase operates. The enzyme, he recognized, works much like telomerase, the specialized reverse transcriptase found in eukaryotes, an evolutionarily distant group of organisms that includes yeast, plants, fungi, and animals. In humans and most other eukaryotes, telomerase creates DNA caps that protect the ends of linear chromosomes. Every time a cell divides, these caps, called telomeres, erode, and without telomerase to replenish them, chromosomes gradually lose protective sequence until cells stop dividing and enter a senescent state. That a bacterial antiviral enzyme and the guardian of human chromosome ends should operate by such similar chemistry was far too striking to dismiss as coincidence.

The functional similarity might have remained an interesting footnote had it not been for a visit to the Sternberg lab by Mario Rodríguez Mestre, a colleague at the University of Copenhagen who uses computational methods to identify and classify bacterial defense systems. During a talk, Mestre presented a preliminary evolutionary tree of all known reverse transcriptases, with branches color-coded by domain of life. One side of the tree was almost entirely brown, representing bacterial enzymes, while the other side was turquoise, representing eukaryotic enzymes. Sternberg interrupted the presentation, intrigued by a narrow turquoise sliver of eukaryotic reverse transcriptases that clustered tightly with the bacterial branch. That sliver turned out to be telomerase. For Sternberg, it was a eureka moment: the functional parallels between DRT10 and telomerase might reflect a shared evolutionary ancestry rather than convergence, unifying what had seemed like two separate fields into a single large family of enzymes.

Additional evolutionary analyses bolstered that interpretation. The data support a common origin for bacterial defense-associated reverse transcriptases and telomerase, indicating that the capacity to synthesize repetitive DNA arose in a shared ancestor and was later adapted by eukaryotes to maintain linear chromosomes. This raises a provocative possibility about the history of life itself. As Sternberg suggests, ancient enzymatic capabilities of a DRT10-like system may have been part of the molecular machinery that allowed the eukaryotic branch of life to emerge with a different, linear chromosomal topology. Bacteria carry their genomes on circular chromosomes that need no end protection, whereas eukaryotes adopted linear chromosomes, which create the telomere problem that telomerase solves. An ancestral DNA-writing enzyme capable of generating repetitive telomeric sequence could therefore have been a prerequisite for the transition, helping set the evolutionary stage for complex organisms.

Beyond its evolutionary significance, the discovery carries immediate translational promise. Telomere shortening drives cells into senescence, and the accumulation of senescent cells is linked to a range of age-related diseases, raising the possibility that restoring telomeres could help preserve healthy cell function. Defects in telomere maintenance also underlie a class of disorders known as telomeropathies, and Sternberg’s team hopes to explore whether DRT10 could eventually be adapted to address them. The lab has already used the enzyme to synthesize human telomeric DNA repeats in human cells and is now working to determine whether lengthening chromosomes can prevent cells from senescing and extend their healthy lifespans. Although the work remains at an early stage, the prospect of turning a bacterial defense enzyme into a tool for rebuilding protective DNA at chromosome ends represents a striking repurposing of microbial immunity for human medicine.

Cancer immunotherapy offers another potential application. CAR-T cell therapy, which engineers a patient’s own T cells to recognize and attack cancer cells, is often limited by the exhaustion and finite lifespan of the therapeutic cells themselves. Because telomere length governs how long a cell can continue dividing, maintaining or lengthening telomeres could help therapeutic T cells remain active for longer periods in patients. DRT10, with its ability to write repetitive DNA from an RNA template, gives researchers a brand-new way to explore that question, and potentially a means of engineering longer-lived cell therapies.

The study also stands as a testament to the value of basic research pursued without a predetermined application in mind. Curiosity about what bacteria do with a family of uncharacterized enzymes has illuminated deep questions about aging, cancer, and the evolution of life, revealing an unexpected connection between microbial antiviral defense and one of the most consequential enzymes in human biology. Columbia University has filed a patent application related to the work, with Sternberg, Tang, and Ramirez listed as inventors, and Sternberg holds advisory roles with several genome-editing companies, signaling commercial interest in the technology. Whether DRT10 matures into a clinical tool for telomeropathies, an enhancer of CAR-T therapy, or a novel platform for writing DNA into genomes, its discovery has already accomplished something profound: it has traced a single molecular thread from the viral wars of bacteria to the chromosome caps that make complex life possible, and offered an awe-inspiring look back at how life evolved.

Subject of Research: A bacterial antiviral reverse transcriptase system, DRT10, and its shared evolutionary origin with eukaryotic telomerase

Article Title: Scientists uncover an ancient link between viral defense and chromosome protection

Article References: Scientists uncover an ancient link between viral defense and chromosome protection. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: DRT10, reverse transcriptase, telomerase, bacterial antiviral defense, telomeres, genome engineering, evolution, senescence, CAR-T cell therapy, telomeropathies, CRISPR, Columbia University