The molecular mechanism of on-demand sterol biosynthesis at organelle contact sites.

Contact-sites are specialized zones of proximity between two organelles, essential for organelle communication and coordination. The formation of contacts between the Endoplasmic Reticulum (ER), and other organelles, relies on a unique membrane environment enriched in sterols. However, how these sterol-rich domains are formed and maintained had not been understood.

In situ studies of membrane biology by cryo-electron tomography.

Cryo-electron tomography (cryo-ET) allows high resolution 3D imaging of biological samples in near-native environments. Thus, cryo-ET has become the method of choice to analyze the unperturbed organization of cellular membranes. Here, we briefly discuss current cryo-ET workflows and their application to study membrane biology in situ, under basal and pathological conditions.

Dynamic kinetochore size regulation promotes microtubule capture and chromosome biorientation in mitosis.

Faithful chromosome segregation depends on the ability of sister kinetochores to attach to spindle microtubules. The outer layer of kinetochores transiently expands in early mitosis to form a fibrous corona, and compacts following microtubule capture. Here we show that the dynein adaptor Spindly and the RZZ (ROD-Zwilch-ZW10) complex drive kinetochore expansion in a dynein-independent manner.

Structure of the MIS12 Complex and Molecular Basis of Its Interaction with CENP-C at Human Kinetochores.

Kinetochores, multisubunit protein assemblies, connect chromosomes to spindle microtubules to promote chromosome segregation. The 10-subunit KMN assembly (comprising KNL1, MIS12, and NDC80 complexes, designated KNL1C, MIS12C, and NDC80C) binds microtubules and regulates mitotic checkpoint function through NDC80C and KNL1C, respectively. MIS12C, on the other hand, connects the KMN to the chromosome-proximal domain of the kinetochore through a direct interaction with CENP-C.

Insights from the reconstitution of the divergent outer kinetochore of Drosophila melanogaster.

Accurate chromosome segregation during mitosis and meiosis is crucial for cellular and organismal viability. Kinetochores connect chromosomes with spindle microtubules and are essential for chromosome segregation. These large protein scaffolds emerge from the centromere, a specialized region of the chromosome enriched with the histone H3 variant CENP-A.

The C-terminal domain from S. cerevisiae Pat1 displays two conserved regions involved in decapping factor recruitment.

Eukaryotic mRNA decay is a highly regulated process allowing cells to rapidly modulate protein production in response to internal and environmental cues. Mature translatable eukaryotic mRNAs are protected from fast and uncontrolled degradation in the cytoplasm by two cis-acting stability determinants: a methylguanosine (m(7)G) cap and a poly(A) tail at their 5' and 3' extremities, respectively. The hydrolysis of the m(7)G cap structure, known as decapping, is performed by the complex composed of the Dcp2 catalytic subunit and its partner Dcp1.

Modular assembly of RWD domains on the Mis12 complex underlies outer kinetochore organization.

Faithful chromosome segregation is mandatory for cell and organismal viability. Kinetochores, large protein assemblies embedded in centromeric chromatin, establish a mechanical link between chromosomes and spindle microtubules. The KMN network, a conserved 10-subunit kinetochore complex, harbors the microtubule-binding interface.

The MIS12 complex is a protein interaction hub for outer kinetochore assembly.

Kinetochores are nucleoprotein assemblies responsible for the attachment of chromosomes to spindle microtubules during mitosis. The KMN network, a crucial constituent of the outer kinetochore, creates an interface that connects microtubules to centromeric chromatin. The NDC80, MIS12, and KNL1 complexes form the core of the KMN network.

Two novel families of plasmids from hyperthermophilic archaea encoding new families of replication proteins.

Thermococcales (phylum Euryarchaeota) are model organisms for physiological and molecular studies of hyperthermophiles. Here we describe three new plasmids from Thermococcales that could provide new tools and model systems for genetic and molecular studies in Archaea. The plasmids pTN2 from Thermococcus nautilus sp.

Crystal structure of yeast FAD synthetase (Fad1) in complex with FAD.

Flavin adenine dinucleotide (FAD) synthetase is an essential enzyme responsible for the synthesis of FAD by adenylation of riboflavin monophosphate (FMN). We have solved the 1.9 A resolution structure of Fad1, the yeast FAD synthetase, in complex with the FAD product in the active site.

Structure, function, and targets of the transcriptional regulator SvtR from the hyperthermophilic archaeal virus SIRV1.

We have characterized the structure and the function of the 6.6-kDa protein SvtR (formerly called gp08) from the rod-shaped virus SIRV1, which infects the hyperthermophilic archaeon Sulfolobus islandicus that thrives at 85 degrees C in hot acidic springs. The protein forms a dimer in solution.

Crystal structure of AFV1-102, a protein from the acidianus filamentous virus 1.

Viruses infecting hyperthermophilic archaea have intriguing morphologies and genomic properties. The vast majority of their genes do not have homologs other than in other hyperthermophilic viruses, and the biology of these viruses is poorly understood. As part of a structural genomics project on the proteins of these viruses, we present here the structure of a 102 amino acid protein from acidianus filamentous virus 1 (AFV1-102).

Crystal structure of AFV3-109, a highly conserved protein from crenarchaeal viruses.

The extraordinary morphologies of viruses infecting hyperthermophilic archaea clearly distinguish them from bacterial and eukaryotic viruses. Moreover, their genomes code for proteins that to a large extend have no related sequences in the extent databases. However, a small pool of genes is shared by overlapping subsets of these viruses, and the most conserved gene, exemplified by the ORF109 of the Acidianus Filamentous Virus 3, AFV3, is present on genomes of members of three viral familes, the Lipothrixviridae, Rudiviridae, and "Bicaudaviridae", as well as of the unclassified Sulfolobus Turreted Icosahedral Virus, STIV.