Miguel Sanchez

Sep7 Is Essential to Modify Septin Ring Dynamics and Inhibit Cell Separation during Candida albicans Hyphal Growth

When Candida albicans yeast cells receive the appropriate stimulus, they switch to hyphal growth, characterized by continuous apical elongation and the inhibition of cell separation. The molecular basis of this inhibition is poorly known, despite its crucial importance for hyphal development. In C. albicans, septins are important for hypha formation and virulence. Here, we used fluorescence recovery after photobleaching analysis to characterize the dynamics of septin rings during yeast and hyphal growth. On hyphal induction, septin rings are converted to a hyphal-specific state, characterized by the presence of a frozen core formed by Sep7/Shs1, Cdc3 and Cdc12, whereas Cdc10 is highly dynamic and oscillates between the ring and the cytoplasm. Conversion of septin rings to the hyphal-specific state inhibits the translocation of Cdc14 phosphatase, which controls cell separation, to the hyphal septum. Modification of septin ring dynamics during hyphal growth is dependent on Sep7 and the hyphal-specific cyclin Hgc1, which partially controls Sep7 phosphorylation status and protein levels. Our results reveal a link between the cell cycle machinery and septin cytoskeleton dynamics, which inhibits cell separation in the filaments and is essential for hyphal morphogenesis.

Orchestrating the cell cycle in yeast: sequential localization of key mitotic regulators at the spindle pole and the bud neck.

1 Departamento de Microbiologı!a II, Facultad de Farmacia, Universidad Complutense de Madrid, 28040 Madrid, Spain 2 Departamento de Microbiologı!a y Gene! tica, Instituto de Microbiologı!a-Bioquı!mica, Edificio Departamental, Campus Miguel de Unamuno, Universidad de Salamanca/CSIC, 37007 Salamanca, Spain 3 Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720, USA

Dbf2 is essential for cytokinesis and correct mitotic spindle formation in Candida albicans

We have characterized the DBF2 gene, encoding a protein kinase of the NDR family in Candida albicans, and demonstrate that this gene is essential for cell viability. Conditional mutants were constructed by using the MET3 promoter to analyse the phenotype of cells lacking this kinase. The absence of Dbf2 resulted in cells arrested as large‐budded pairs that failed to contract the actomyosin ring, a function similar to that described for its Saccharomyces cerevisiae orthologue. In addition to its role in cytokinesis, Dbf2 regulates mitotic spindle organization and nuclear segregation as Dbf2‐depleted cells have abnormal microtubules and severe defects in nuclear migration to the daughter cell, which results in a cell cycle block during mitosis. Taken together, these results imply that Dbf2 performs several functions during exit from mitosis and cytokinesis. Consistent with a role in spindle organization, the protein localizes to the mitotic spindle during anaphase, and it interacts physically with tubulin, as indicated by immunoprecipitation experiments. Finally, DBF2 depletion also resulted in impaired true hyphal growth.

Comprehensive transient-state study for CARMENES NIR high-thermal stability

CARMENES has been proposed as a next-generation instrument for the 3.5m Calar Alto Telescope. Its objective is finding habitable exoplanets around M dwarfs through radial velocity measurements (m/s level) in the near-infrared. Consequently, the NIR spectrograph is highly constraint regarding thermal/mechanical requirements. Indeed, the requirements used for the present study limit the thermal stability to ±0.01K (within year period) over a working temperature of 243K in order to minimise radial velocity drifts. This can be achieved by implementing a solution based on several temperature-controlled rooms (TCR), whose smallest room encloses the vacuum vessel which houses the spectrographs optomechanics. Nevertheless, several options have been taken into account to minimise the complexity of the thermal design: 1) Large thermal inertia of the system, where, given a thermal instability of the environment (typically, ±0.1K), the optomechanical system remains stable within ±0.01K in the long run; 2) Environment thermal control, where thermal stability is ensured by controlling the temperature of the environment surrounding the vacuum vessel. The present article also includes the comprehensive transient-state thermal analyses which have been implemented in order to make the best choice, as well as to give important inputs for the thermal layout of the instrument.

Structure-function relationships in nucleosomal arrays containing linker histone H5.

To study the structural and functional changes accompanying the integration of histone H5 into the nucleosome structure, linear DNA species have been employed with a terminal promoter for bacteriophage T7 RNA polymerase followed by tandem repeats of a 207-bp nucleosome positioning sequence. The oligonucleosomes assembled from 12-repeat DNA and saturating amounts of core histone octamer plus histone H5 are compacted, in the presence of 1 mM free magnesium ions, to the level of the 30-nm fiber. Under these ionic conditions the efficiency in RNA synthesis and the size distribution of RNA chains obtained with this template are the same as those corresponding to the template without H5, indicating that the 30-nm fiber stabilized by H5 does not impair RNA elongation. Therefore, under our experimental conditions, incorporation of one molecule of histone H5 per nucleosome does not affect elongation of RNA even when a folded structure is produced. However, elongation is inhibited by binding of an excess of H5.

Aproximación histórica a la intervención humanitaria. Debates y enfoques

Introduccion Aunque a la vista de ciertos acontecimientos recientes cueste creerlo, las sociedades se han esforzado siempre por generar mecanismos orientados a paliar la suerte de aquellos individuos que, por diversas causas, no alcanzaban a disponer de la totalidad de sus facultades. Doctrinas religiosas, principios eticos y fundamentos filosoficos han sustentando a lo largo de la Historia la ayuda a los llamados«desvalidos» y, sin lugar a dudas, los tiempos de guerra se han mostrado como el mejor contexto en el que desplegar dichos propositos. En el ambito belico, la confeccion de normas que permitan distinguir claramente que personas han de ser respetadas en determinadas circunstancias dentro del campo de batalla podria remontarse a los codigos de la caballeria medieval, si no antes. Andando el tiempo, y ya con el patrocinio de las Monarquias modernas, hallamos ejemplos mas acabados de proteccion a las victimas (eso si, a las del propio bando) como el Hospital de Malinas (Brabante) que Felipe II fundo en 1567 para asistencia a los miembros del ejercito permanente de Flandes, perdurando dicha institucion, no sin altibajos, hasta 17061. Asi pues, existen antecedentes fundamentales para la magna obra que se llevo a cabo en la segunda mitad del siglo XIX cuando en el arranque del proceso de unificacion italiana y en medio de la conflagracion