A Ca-regulated deAMPylation switch in human and bacterial FIC proteins.

FIC proteins regulate molecular processes from bacteria to humans by catalyzing post-translational modifications (PTM), the most frequent being the addition of AMP or AMPylation. In many AMPylating FIC proteins, a structurally conserved glutamate represses AMPylation and, in mammalian FICD, also supports deAMPylation of BiP/GRP78, a key chaperone of the unfolded protein response. Currently, a direct signal regulating these FIC proteins has not been identified.

Small GTPase peripheral binding to membranes: molecular determinants and supramolecular organization.

Small GTPases regulate many aspects of cell logistics by alternating between an inactive, GDP-bound form and an active, GTP-bound form. This nucleotide switch is coupled to a cytosol/membrane cycle, such that GTP-bound small GTPases carry out their functions at the periphery of endomembranes. A global understanding of the molecular determinants of the interaction of small GTPases with membranes and of the resulting supramolecular organization is beginning to emerge from studies of model systems.

FIC proteins: from bacteria to humans and back again.

During the last decade, FIC proteins have emerged as a large family comprised of a variety of bacterial enzymes and a single member in animals. The air de famille of FIC proteins stems from a domain of conserved structure, which catalyzes the post-translational modification of proteins (PTM) by a phosphate-containing compound. In bacteria, examples of FIC proteins include the toxin component of toxin/antitoxin modules, such as Doc-Phd and VbhT-VbhA, toxins secreted by pathogenic bacteria to divert host cell processes, such as VopS, IbpA and AnkX, and a vast majority of proteins of unknown functions.

Characterization of the activation of small GTPases by their GEFs on membranes using artificial membrane tethering.

Active, GTP-bound small GTPases need to be attached to membranes by post-translational lipid modifications in order to process and propagate information in cells. However, generating and manipulating lipidated GTPases has remained difficult, which has limited our quantitative understanding of their activation by guanine nucleotide exchange factors (GEFs) and their termination by GTPase-activating proteins. Here, we replaced the lipid modification by a histidine tag in 11 full-length, human small GTPases belonging to the Arf, Rho and Rab families, which allowed to tether them to nickel-lipid-containing membranes and characterize the kinetics of their activation by GEFs.

Sodium selenide toxicity is mediated by O2-dependent DNA breaks.

Hydrogen selenide is a recurrent metabolite of selenium compounds. However, few experiments studied the direct link between this toxic agent and cell death. To address this question, we first screened a systematic collection of Saccharomyces cerevisiae haploid knockout strains for sensitivity to sodium selenide, a donor for hydrogen selenide (H(2)Se/HSe(-/)Se(2-)).

Rpa43 and its partners in the yeast RNA polymerase I transcription complex.

An Rpa43/Rpa14 stalk protrudes from RNA polymerase I (RNAPI), with homology to Rpb7/Rpb4 (RNAPII), Rpc25/Rpc17 (RNAPIII) and RpoE/RpoF (archaea). In fungi and vertebrates, Rpa43 contains hydrophilic domains forming about half of its size, but these domains lack in Schizosaccharomyces pombe and most other eukaryote lineages. In Saccharomyces cerevisiae, they can be lost with little or no growth effect, as shown by deletion mapping and by domain swapping with fission yeast, but genetically interact with rpa12Δ, rpa34Δ or rpa49Δ, lacking non-essential subunits important for transcript elongation.

The A14-A43 heterodimer subunit in yeast RNA pol I and their relationship to Rpb4-Rpb7 pol II subunits.

A43, an essential subunit of yeast RNA polymerase I (pol I), interacts with Rrn3, a class I general transcription factor required for rDNA transcription. The pol I-Rrn3 complex is the only form of enzyme competent for promoter-dependent transcription initiation. In this paper, using biochemical and genetic approaches, we demonstrate that the A43 polypeptide forms a stable heterodimer with the A14 pol I subunit and interacts with the common ABC23 subunit, the yeast counterpart of the omega subunit of bacterial RNA polymerase.