Volume 22 Issue 3, March 2015

Mapping of ribonucleotides to single-nucleotide resolution in yeast genomes provides new insight into the enzymology of DNA replication.

During infection, pathogenic Yersinia species secrete the antiphagocytic factor YopO (or YpkA), which contains a kinase domain and a Rho GTPase guanine nucleotide–dissociation inhibitor (GDI) domain. The structure of YopO in complex with actin, along with biochemical analyses, reveals the mechanism by which YopO uses actin to activate its kinase domain and recruit, phosphorylate and deactivate actin-assembly factors implicated in phagocytic clearance of the bacterium.

A chaperone segment provides powerful evidence for the molecular mechanism underlying Alzheimer's disease.

Amyloids escape elimination by the proteasome, and their accumulation and subsequent aggregation contribute to various neurodegenerative conditions. A signature feature of amyloidogenic proteins is extended sequences rich in single amino acids. In this issue, Matouschek and colleagues now show that, to initiate degradation, the proteasome prefers substrates that have disordered regions with complex amino acid composition, thus indicating why it fails to rid the cell of most amyloids.

HydEn-seq, a new sequencing method that maps the distribution of ribonucleotides misincorporated by low-fidelity DNA polymerases in budding yeast, reveals unexpected strand-specific replication patterns in both nuclear and mitochondrial genomes.

Genome-wide DNA polymerase usage maps determined in fission yeast, using a new sequencing strategy based on ribonucleotide misincorporation, track the division of labor between replicative polymerases and reveal locations and efficiencies of replication origins.

The neuronal sorting receptor SorLA protects against Alzheimer's disease by binding Aβ peptides. Three new structures of the Vps10p Aβ-binding domain in ligand-free and ligand-bound forms explain the basis of SorLA peptide recognition.

Aβ peptide aggregation is associated with Alzheimer's disease, and Aβ fibrils can catalyze formation of toxic oligomers. Molecular chaperone Brichos binds to the fibril surface, inhibiting the catalytic cycle in vitro, and limits Aβ toxicity.

The proteasome initiates protein degradation at disordered regions within substrates. The proteasomal sequence preferences for the amino acid composition of these regions identified here affect protein half-life and explain unusual stability trends.

Tumor-suppressor protein CYLD cleaves linear and Lys63-linked ubiquitin chains. Structures of CYLD USP domain with Met1- and Lys63-linked diubiquitins and biochemical analyses reveal the mechanism for dual specificity and provide insight into tumor-associated mutations.

Human DNA Polθ can mediate microhomology-mediated end-joining (MMEJ) of DNA molecules in cells and in vitro. Biochemistry work shows that Polθ promotes formation of DNA synapses and strand annealing, activities that require insertion loop 2.

Crystal structures of the bacterial vitamin C transporter UlaA, a member of the AG family of the phosphoenolpyruvate-dependent phosphotransferase system, provide insights on binding to ascorbate and its transport across the cell membrane.

New biochemical analyses in Xenopus cell-free extracts show that two replication forks must converge on a DNA interstrand cross-link (ICL) to permit translesion synthesis and repair.

The crystal structure of Yersinia enterocolitica kinase YopO in complex with monomeric actin, together with biochemical analyses, reveals that YopO uses actin as bait to disrupt host cytoskeleton function and prevent phagocytosis.

The identification of a new subclass of circular RNAs that are predominantly nuclear and promote transcription of their parental genes reveals a new regulatory function for these noncoding RNAs.

Serial femtosecond crystallography of the human δ-opioid receptor in complex with an endomorphin-derived peptide reveals interactions that are important for understanding the pharmacology of opioid peptides and developing analgesics with reduced side effects.

A high-resolution cryo-EM structure of yeast eIF3-bound 40S ribosomal subunits reveals the network of interactions between eIF3 subunits.