Volume 22 Issue 5, May 2015

Mammalian cells have both cytoplasmic and mitochondrial ribosomes, which have long been considered to operate completely independently. However, a new report shows that after heat shock, MRPL18, a human mitochondrial ribosomal protein, binds to cytoplasmic ribosomes to influence translation of heat-shock mRNAs.

The first structures of a light-driven sodium pump provide insight into the mechanism of ion transport and selectivity. Genetic manipulation of rat neuronal cells and of Caenorhabditis elegans worms demonstrates the utility of such pumps for optogenetic applications.

The identification of a second regulatory checkpoint controlling RNA polymerase II elongation near the poly(A) site of protein-coding genes reveals an additional level of complexity in the modulation of eukaryotic transcriptional elongation and termination.

Regulation of integrin activity is critical for human health, and the steps mediating integrin activation are well established. In contrast, the counteracting mechanisms of inactivation are less understood. An integrin inhibitor, filamin, is shown to stabilize the integrin resting state by bondage of the cytoplasmic domains of the integrin heterodimer, thus providing evidence of a new mechanism for integrin retention in the inactive state.

R-type pyocins, produced by Pseudomonas aeruginosa, are sheath-tube nanomachines that puncture the envelopes of target cells, inducing their death. Cryo-EM studies reveal the atomic structures of the pyocin R2 in its extended precontraction and postcontraction forms, which suggest a mechanism for the contraction process of this molecular syringe.

Dynactin is an essential cofactor for the microtubule-based motor cytoplasmic dynein. Two recent papers report structures obtained by cryo-EM of dynactin, the dynein–dynactin complex and dynein–dynactin bound to its track, the microtubule.

Roth and colleagues have developed PRESTO-Tango, a new open-source platform for high-throughput screening of the entire human nonolfactory GPCRome, and they show how it can be used to identify new ligands for orphan human GPCRs.

The evolutionarily conserved antisense long noncoding RNA asFGFR2 influences cell type–specific alternative-splicing patterns of FGFR2 by recruiting chromatin modifiers to the locus.

Cryo-EM structures of the pre- and postcontraction states of Pseudomonas aeruginosa R-type pyocins provide details of the conformational changes between the tube and sheath that take place during contraction.

The integrin inhibitor filamin competes with activators for integrin binding, but an NMR structural analysis now reveals that filamin also functions by stabilizing integrin in its resting state.

Crystal structures of the microbial rhodopsin KR2, a recently discovered light-driven sodium pump, reveal the translocation pathway of sodium ions and shed light on the molecular mechanism of ion pumping.

Genome-wide mapping of CDK9-dependent transcription-elongation checkpoints reveals an unexpected control point near the poly(A) site of pol II–transcribed human genes.

A stress-induced cytosolic isoform of the mitochondrial ribosomal protein MRPL18 facilitates the specific translation of heat-shock proteins during the general shutdown of protein synthesis that occurs in response to cellular stress.

The hexameric ClpX AAA+ ATPase requires subunit asymmetry and switching between nucleotide-loadable and nucleotide-unloadable conformations for cooperative ATP hydrolysis and efficient substrate binding, unfolding and degradation.

Assays in both C. elegans and human cells show that Notch interacts with ATM kinase to inhibit the DNA-damage response and that Notch activity is inversely correlated with ATM activation in breast cancer cells.

Solving the crystal structure of the Y-complex hub allowed Schwartz and colleagues to assemble a high-resolution composite structure of the complete Y complex, one of the principal nuclear pore complex scaffolds.