Structural studies put phage defense mystery on the RADAR.

Phage restriction by adenosine deaminase acting on RNA (RADAR) is a process by which bacteria may alter their own transcriptome to resist bacteriophage. In this issue of Cell, Duncan-Lowey and Tal et al. and Gao et al.

Recent advances in the structural biology of encapsulin bacterial nanocompartments.

Large capsid-like nanocompartments called encapsulins are common in bacteria and archaea and contain cargo proteins with diverse functions. Advances in cryo-electron microscopy have enabled structure determination of many encapsulins in recent years. Here we summarize findings from recent encapsulin structures that have significant implications for their biological roles.

Cryo-EM structure of a thermostable bacterial nanocompartment.

Protein nanocompartments are widespread in bacteria and archaea, but their functions are not yet well understood. Here, the cryo-EM structure of a nanocompartment from the thermophilic bacterium is reported at 2.0 Å resolution.

Determinants of adenine-mutagenesis in diversity-generating retroelements.

Diversity-generating retroelements (DGRs) vary protein sequences to the greatest extent known in the natural world. These elements are encoded by constituents of the human microbiome and the microbial 'dark matter'. Variation occurs through adenine-mutagenesis, in which genetic information in RNA is reverse transcribed faithfully to cDNA for all template bases but adenine.

SHAPE Profiling to Probe Group II Intron Conformational Dynamics During Splicing.

Selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) is a widely used technique for studying the structure and function of RNA molecules. It characterizes the flexibility of single nucleotides in the context of the local RNA structure. Here we describe the application of SHAPE-MaP (mutational profiling) to study different conformational states of the group II intron during the self-splicing reaction.

Structural basis for the second step of group II intron splicing.

The group II intron and the spliceosome share a common active site architecture and are thought to be evolutionarily related. Here we report the 3.7 Å crystal structure of a eukaryotic group II intron in the lariat-3' exon form, immediately preceding the second step of splicing, analogous to the spliceosomal P complex.

Structure determination of group II introns.

Group II introns are self-splicing catalytic RNAs that are able to excise themselves from pre-mRNAs using a mechanism identical to that utilized by the spliceosome. Both structural and phylogenetic data support the hypothesis that group II introns and the spliceosome share a common ancestor. Structures of group II introns have given insight into the active site required for the catalysis of RNA splicing.