Antiviral immunity via telomerase-like reverse transcription in bacteria.

October 12, 2026| Source: Nature

Defense-associated reverse transcriptases (DRTs) employ diverse and distinctive mechanisms of cDNA synthesis to protect bacteria against viral infection 1 . However, the functions and mechanisms of many DRTs remain unknown 2 . Here we identify a new antiviral defense system, DRT10, that associates with a noncoding RNA (ncRNA) to catalyze processive, protein-primed synthesis of tandem-repeat DNA. Reverse transcription is templated by a defined ncRNA region with a characteristic sequence pattern and template boundary elements, both of which are conserved and essential for DNA repeat addition. Cryo-EM reconstructions reveal an unanticipated 2:1 architecture, wherein two RT monomers bind opposite sides of a pseudo-symmetric ncRNA. Biochemical experiments further demonstrate that each RT monomer reverse transcribes the template encoded on its respective side of the ncRNA, but only one generates the long repetitive product, whose template is defined by the distance between two flanking stem-loop anchors. This mode of iterative, boundary-delimited cDNA synthesis exhibits direct parallels to the mechanism of telomeric repeat addition by eukaryotic telomerase, and phylogenetic analyses of RTs across domains of life place telomerase in a monophyletic clade with the DRT family, suggesting a common origin for their DNA polymerization activities. Together with earlier studies of DRT2, DRT3, and DRT9 3-5 , our findings identify a conserved mechanistic logic underlying RNA-templated DNA repeat addition across diverse DRTs, despite vastly different architectural solutions, and expand the repertoire of reverse transcription-based strategies for antiviral immunity in bacteria.

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Extensive glacier loss in the coterminous United States.

Glaciers populate the mountain ranges of the western conterminous United States and despite their importance to alpine hydrology, their area and volume change have never been comprehensively evaluated. Our study shows that since the mid-twentieth century about one-quarter of the glaciers have disappeared and the overall area and volume are reduced by one-third. The pattern of glacier shrinkage suggests most glaciers in the conterminous United States are largely maintained by local topographic in

Physical/TechOctober 20, 2026

Reaction-based cryo-EM resolves the continuous conformational spectrum of CTP synthase catalysis.

Capturing enzymes under native turnover conditions remains a grand challenge in structural biology. Here, we develop a reaction-based cryo-electron microscopy (cryo-EM) strategy that directly samples Drosophila melanogaster cytidine triphosphate synthase (CTPS) from actively catalyzing mixtures containing only natural substrates and allosteric effectors. By integrating reaction-based sampling with three-dimensional variability analysis, we resolve a continuous conformational spectrum of CTPS dur

Physical/TechOctober 20, 2026

GTP orchestrates CTP synthase via an allosteric effector-cycling mechanism.

Cytidine triphosphate (CTP), a fundamental building block of RNA, plays vital roles in diverse biological processes. CTP synthase (CTPS) is the only known enzyme for de novo synthesis of CTP. Efficient CTPS catalysis requires guanosine triphosphate (GTP) in a dose-dependent, nonconsumptive manner; however, the precise mechanism by which GTP drives CTP formation remains unclear. Here, we integrate a series of cryo-EM structures of Drosophila melanogaster CTPS captured from actively catalyzing sam

Physical/TechOctober 20, 2026

Antiferromagnetism and tightly bound Cooper pairs induced by kinetic frustration.

Antiferromagnetism and superconductivity are often viewed as competing orders in correlated electron systems. Here, we demonstrate that kinetic frustration in hole motion facilitates their coexistence within the square-lattice repulsive Hubbard model. Combining exact analytical solutions on tailored geometries with large-scale numerical simulations, we reveal a robust pairing mechanism: Holes on opposite sublattices behave as if they carry opposite effective charges due to spin singlet formation

Physical/TechOctober 20, 2026

Coordinated transformations of the labyrinth and occiput during the dinosaur-bird transition.

Evolutionary shape changes of the vertebrate semicircular canals (SCCs) are often ascribed to evolutionary transitions in locomotion, including the origin of flight during the dinosaur-bird transition. However, the potential for transformations of braincase architecture to influence SCC shape independent of sensory-functional adaptation has generally been overlooked. We evaluate the influence of both factors using a large dataset of 146 living and recently extinct crown birds, including taxa rep