Sperm flagella of highly divergent eukaryotic species share an architectural plan. Despite their ostensible ultrastructural similarities, mammalian sperm flagella beat with an asymmetric waveform, in contrast to the symmetrical beats of other eukaryotic flagella. Structural findings elucidate the molecular basis for this evolutionary divergence.

Recent studies offer new insight on the mechanisms of IP6-mediated HIV-1 capsid assembly. The immature Gag lattice enables enrichment of IP6 into virions, aiding capsid maturation. Structures of capsid protein (CA) assemblies reveal motifs serving as switches modulating the conformations of CA pentamers/hexamers and affect co-factor accessibility.

The RNA methyltransferase (MTase) METTL1 catalyzes N⁷-methylguanosine (m⁷G) modification at position 46 in human transfer RNAs (tRNAs). Its dysregulation drives tumorigenesis in many cancer types. Two papers now reveal the structural basis of this tRNA maturation event.

The authors solve cryo-EM structures of the alkaline pH-induced insulin receptor-related receptor (IRR), providing clues into its activation mechanism by pH.

Here, using cryo-EM, the authors detail how the yeast co-transcriptional assembly of the large ribosomal subunit involves a quality-control checkpoint. Ribosome-assembly factors implement this checkpoint by probing the formation and ensuring the co-operative stabilization of correctly folded ribosomal RNA.

Here, the authors show that common fragile sites are unstable under loose activation of the DNA-replication checkpoint. Tight checkpoint activation or CDK1 inhibition stabilizes them by advancing completion of their replication via extra replication-initiation events that are dependent on S-phase availability of proteins involved in pre-RC building.

Here the authors investigate the contribution of transposable elements to regulation of gene expression in human trophoblasts. Amongst other examples, they identify an LTR10A element with potential implications for preeclampsia.

Here, the authors biochemically demonstrate how the Smc5/6 SMC compartment holds a DNA loop by topologically entrapping DNA in two SMC subcompartments and the kleisin compartment. This mechanism requires the Nse5/6 loader to open the neck gate before DNA entrance.

Fluorine nuclear magnetic resonance spectroscopy of the stimulatory heterotrimeric G protein reveals a conformational landscape shaped by interactions with nucleotides, the lipid bilayer and a G-protein-coupled receptor.