A global view of substrate phosphorylation and dephosphorylation during budding yeast mitotic exit

The cell cycle is the process by which a cell duplicates its DNA during S-phase and divides its chromosomes during M-phase, creating two genetically identical daughter cells. Cell cycle events are ordered by synthesis and degradation of key cell regulators and by phosphorylation and dephosphorylation of numerous substrates. Phosphorylation can alter the activity, interactions or subcellular localization of a protein. A substrate’s phosphorylation status is the readout of competing activities of kinases and phosphatases that target each of its phosphorylation sites. In our recent study (EMBO J. 37, e98745), we performed time-resolved global phosphoproteome analysis of a period during the cell cycle known as mitotic exit. During this time, numerous cell biological events happen in fast succession but in strict order. First, at the metaphase to anaphase transition, the mitotic spindle elongates to pull maximally condensed chromosomes to opposite cell halves. Shortly after that, spindles disassemble and chromosomes decondense, before finally cell division is completed by cytokinesis. Our time-resolved phosphoproteome analysis of this period in budding yeast provided a survey of the principles of phosphoregulation used to order these events

The PP2A inhibitor I2PP2A is essential for sister chromatid segregation in oocyte meiosis II.

Haploid gametes are generated through two consecutive meiotic divisions, with the segregation of chromosome pairs in meiosis I and sister chromatids in meiosis II. Separase-mediated stepwise removal of cohesion, first from chromosome arms and later from the centromere region, is a prerequisite for maintaining sister chromatids together until their separation in meiosis II [1]. In all model organisms, centromeric cohesin is protected from separase-dependent removal in meiosis I through the activity of PP2A-B56 phosphatase, which is recruited to centromeres by shugoshin/MEI-S332 (Sgo) [2-5]. How this protection of centromeric cohesin is removed in meiosis II is not entirely clear; we find that all the PP2A subunits remain colocalized with the cohesin subunit Rec8 at the centromere of metaphase II chromosomes. Here, we show that sister chromatid separation in oocytes depends on a PP2A inhibitor, namely I2PP2A. I2PP2A colocalizes with the PP2A enzyme at centromeres at metaphase II, independently of bipolar attachment. When I2PP2A is depleted, sister chromatids fail to segregate during meiosis II. Our findings demonstrate that in oocytes I2PP2A is essential for faithful sister chromatid segregation by mediating deprotection of centromeric cohesin in meiosis II

How oocytes try to get it right: spindle checkpoint control in meiosis

International audienceThe generation of a viable, diploid organism depends on the formation of haploid gametes, oocytes, and spermatocytes, with the correct number of chromosomes. Halving the genome requires the execution of two consecutive specialized cell divisions named meiosis I and II. Unfortunately, and in contrast to male meiosis, chromosome segregation in oocytes is error prone, with human oocytes being extraordinarily ``meiotically challenged''. Aneuploid oocytes, that are with the wrong number of chromosomes, give rise to aneuploid embryos when fertilized. In humans, most aneuploidies are lethal and result in spontaneous abortions. However, some trisomies survive to birth or even adulthood, such as the well-known trisomy 21, which gives rise to Down syndrome (Nagaoka et al. in Nat Rev Genet 13:493-504, 2012). A staggering 20-25 % of oocytes ready to be fertilized are aneuploid in humans. If this were not bad enough, there is an additional increase in meiotic missegregations as women get closer to menopause. A woman above 40 has a risk of more than 30 % of getting pregnant with a trisomic child. Worse still, in industrialized western societies, child birth is delayed, with women getting their first child later in life than ever. This trend has led to an increase of trisomic pregnancies by 70 % in the last 30 years (Nagaoka et al. in Nat Rev Genet 13:493-504, 2012; Schmidt et al. in Hum Reprod Update 18:29-43, 2012). To understand why errors occur so frequently during the meiotic divisions in oocytes, we review here the molecular mechanisms at works to control chromosome segregation during meiosis. An important mitotic control mechanism, namely the spindle assembly checkpoint or SAC, has been adapted to the special requirements of the meiotic divisions, and this review will focus on our current knowledge of SAC control in mammalian oocytes. Knowledge on how chromosome segregation is controlled in mammalian oocytes may help to identify risk factors important for questions related to human reproductive health

Mouse oocytes depend on BubR1 for proper chromosome segregation but not for prophase I arrest

International audienceMammalian female meiosis is error prone, with rates of meiotic chromosome missegregations strongly increasing towards the end of the reproductive lifespan. A strong reduction of BubR1 has been observed in oocytes of women approaching menopause and in ovaries of aged mice, which led to the hypothesis that a gradual decline of BubR1 contributes to age-related aneuploidization. Here we employ a conditional knockout approach in mouse oocytes to dissect the meiotic roles of BubR1. We show that BubR1 is required for diverse meiotic functions, including persistent spindle assembly checkpoint activity, timing of meiosis I and the establishment of robust kinetochore–microtubule attachments in a meiosis-specific manner, but not prophase I arrest. These data reveal that BubR1 plays a multifaceted role in chromosome segregation during the first meiotic division and suggest that age-related decline of BubR1 is a key determinant of the formation of aneuploid oocytes as women approach menopause

Phosphorylation of the F-BAR protein Hof1 drives septin ring splitting in budding yeast

Abstract A double septin ring accompanies cytokinesis in yeasts and mammalian cells. In budding yeast, reorganisation of the septin collar at the bud neck into a dynamic double ring is essential for actomyosin ring constriction and cytokinesis. Septin reorganisation requires the Mitotic Exit Network (MEN), a kinase cascade essential for cytokinesis. However, the effectors of MEN in this process are unknown. Here we identify the F-BAR protein Hof1 as a critical target of MEN in septin remodelling. Phospho-mimicking HOF1 mutant alleles overcome the inability of MEN mutants to undergo septin reorganisation by decreasing Hof1 binding to septins and facilitating its translocation to the actomyosin ring. Hof1-mediated septin rearrangement requires its F-BAR domain, suggesting that it may involve a local membrane remodelling that leads to septin reorganisation. In vitro Hof1 can induce the formation of intertwined septin bundles, while a phosphomimetic Hof1 protein has impaired septin-bundling activity. Altogether, our data indicate that Hof1 modulates septin architecture in distinct ways depending on its phosphorylation status

Beno[C][1,2,5]oxadiazole for the treatment of diseases caused by Helicobacter

The present invention relates to new compounds which are benzo[c][1,2,5]oxadiazole derivatives, and the use thereof in the treatment of infectious diseases caused by Helicobacter pylori. Also, the present invention relates to a pharmaceutical composition and to a combined preparation both comprising said compoundsPeer reviewedUniversidad de Zaragoza, Consejo Superior de Investigaciones Científicas (España), Fundación Instituto de Investigación Sanitaria de Aragón, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Instituto PasteurA1 Solicitud de patente con informe sobre el estado de la técnic

Compuestos para el tratamiento de enfermedades causadas por Helicobacter

Compuestos para el tratamiento de enfermedades causadas por Helicobacter. La presente invención se refiere a nuevos compuestos que son benzo [c] [1,2,5] oxadiazol. derivados, y su uso en el tratamiento de enfermedades infecciosas causadas por Helicobacter pylori. Además, la presente invención se refiere a una composición farmacéutica y a una preparación combinada que comprende dichos compuestos.Peer reviewedUniversidad de Zaragoza, Consejo Superior de Investigaciones Científicas (España), Fundación Instituto de Investigación Sanitaria de Aragón, Fundación Agencia Aragonesa para la Investigación y Desarrollo, Institut PasteurA1 Solicitud de patente con informe sobre el estado de la técnic

A new approach for Helicobacter pylori eradication: In vivo assessment of novel flavodoxin inhibitors efficacy

Resumen del póster presentado a la VIII National Congress of the Institute for Biocomputation and Physics of Complex Systems (BIFI), celebrado en Zaragoza (España) del 31 de enero al 2 de febrero de 2017.Peer reviewe

Combating bacterial multidrug resistance: new drugs against Helicobacter pylori

Resumen del póster presentado al VIII International Congress BIFI: "Complexity, Networks and Collective Behaviour", celebrado en Zaragoza (España) del 6 al 8 de febrero de 2018.Peer reviewe

Fighting superbugs: new promising compounds against Helicobacter pylori

Resumen del trabajo presentado a la XII Reunión del Grupo Microbiología Molecular de la Sociedad Española de Microbiología, celebrada en Zaragoza del 5 al 7 de septiembre de 2018.Peer Reviewe