Nucleases articles from across Nature Portfolio

The authors perform cryo-EM of pre-tRNA in complex with the human tRNA splicing endonuclease complex TSEN to understand the basis of pre-tRNA recognition and processing by TSEN.

The authors employ cryogenic electron microscopy and kinetic analysis to characterize the discrete steps of how the Dis3L2 3′–5′ exoribonuclease recognizes and degrades structured RNA targets.

Observing the natural process of RNA degradation in real-time is a significant challenge. Here, the authors develop and use single-exonuclease nanocircuits to reveal the single-base degradation behaviour of PNPase, and demonstrate proof-of-principle RNA sequencing using this approach.

Antimicrobial toxins are secreted by bacteria to kill rival species. Here the authors report the mechanism of inhibition of EsaD, a toxin secreted by some S. aureus strains to kill competitors that lack the antitoxin EsaG, showing marked mechanistic differences to other Type II toxin-antitoxin systems.

A PAMless CRISPR nuclease is applied for precision DNA cleavage and cloning.

Contact-dependent growth inhibition (CDI) is an important mechanism of bacterial competition. Here, Bartelli et al. show that proteolytic processing of a CDI toxin induces a conformational switch required for translocation into target bacteria.

Craspase is newly identified type III CRISPR–Cas system with two major components: the nuclease Cas7-11, and the protease TPR-CHAT. Craspases perform a delicate balancing act between nuclease and protease activity to achieve immune tolerance and defense in bacteria, and show promise as highly regulatable genome-editing tools.

The CRISPR–Cas enzyme Cas9 faces the challenge of identifying a specific nucleotide sequence within double-stranded DNA. New cryo-EM and biochemical studies show that in the earliest steps of binding, Cas9 bends the DNA and promotes unwinding of two base pairs, enabling it to efficiently scan the sequence of this critical region.

A series of new cryo-EM structures reveals a surprising twist in how the RAG complex initiates V(D)J recombination. The initial complex with substrate DNA adopts two conformations: in one, the DNA is relatively undistorted but the scissile phosphate is far from the active site, and in the other the DNA is partially melted and unwound by half a turn, which allows the scissile phosphate to dock into the active site. Similar pre-catalysis DNA melting may occur with other DDE recombinases, for which equivalent complexes with uncleaved substrate DNA are not yet available.

DROSHA and its partner DGCR8 form a heterotrimeric complex named Microprocessor, which is essential for microRNA biogenesis. A recent study by Kwon et al. in Cell reveals the structure of a DROSHA construct in complex with the C-terminal region of DGCR8, thereby unveiling the topology and interactions between components of the Microprocessor and insights into its 'ruler'-based cleavage activity and function.