4,613 research outputs found
Derived equivalence and non-vanishing loci II
No full textWe prove a few cases of a conjecture on the invariance of cohomological support loci under derived equivalence by establishing a concrete connection with the related problem of the invariance of Hodge numbers. We use the main case in order to study the derived behavior of fibrations over curves
Insights into the activation mechanism of PopA, a cyclic di-GMP effector protein involved in cell cycle and development of "Caulobacter Crescentus"
No full textIn Caulobacter crescentus, a complex network integrating cyclic di-GMP and Phosphorylation-dependent signals controls the proteolysis of key regulatory proteins to drive cell cycle and polar morphogenesis. The c-di-GMP input is processed by the effector protein PopA. Upon binding of c-di-GMP, PopA is sequestered to the old cell pole where it recruits the replication and cell division inhibitors CtrA and KidO and mediates their destruction by the polar ClpXP protease prior to entry into S-phase. In addition to its role at the stalked cell pole, PopA localizes to the opposite cell pole in dependence of the general topology factor PodJ where it exerts a yet unknown function.
Here we address the activation and polar sequestration mechanism of PopA guided by an existing activation model for the highly homologous c-di-GMP signaling protein PleD. PopA and PleD do not only share an identical domain organization (Rec1-Rec2-GGDEF), but also show similar spatio-temporal behavior during the cell cycle. While PleD is activated and targeted to the old cell pole via phosphorylation-induced dimerization, we show that PopA stalked pole function is phosphorylation-independent and requires c-di-GMP binding as a primary input signal for activation and polar localization. c-di-GMP binds to conserved primary and secondary I-sites within the PopA GGDEF domain and we show that intact binding sites are required for PopA positioning and function. This suggests that c-di-GMP-dependent crosslinking of adjacent GGDEF domains contributes to the localization of an active PopA dimer to the cell pole. Consistent with this, we demonstrate that the GGDEF domain encodes the polar localization signal(s), while the N-terminal receiver domains serve as interaction platform for downstream components that are actively recruited by PopA.
Among these downstream factors is RcdA, a small mediator protein that interacts with the first PopA receiver domain and helps to recruit and degrade CtrA and KidO. In a screen for additional components of the PopA pathway we identify two novel proteins that directly interact with PopA, CC1462 and CC2616. CC1462 is a ClpXP substrate that requires PopA for polar positioning and subsequent degradation during swarmer-to-stalked cell transition. Although located in a flagellar gene cluster, deletion of CC1462 did not affect flagellar assembly and function. Its cellular role as well as the significance of its cell cycle-dependent degradation requires further studies. CC2616, the second PopA interaction partner, is not proteolytically processed and thus belongs to another class of PopA-dependent substrates. CC2616 is annotated as guanine deaminase, which is predicted to catalyze the conversion from guanine to xanthine thereby irreversibly removing guanine based nucleotides from a cellular pool. A CC2616 deletion leads to increased attachment and decreased motility, a phenocopy of strains with elevated c-di-GMP levels. It is not clear whether CC2616 indeed has deaminase activity or whether it has adopted a novel function.
Taken together, this work provides insight into the activation mechanism of a c-di-GMP effector protein. We propose that PopA has evolved through gene duplication from its ancestor, the catalytic PleD response regulator but has lost catalytic activity of the diguanylate cyclase domain. Moreover, PopA has adopted an inverse intra-molecular information transfer originating through c-di-GMP binding at the C-terminal GGDEF domain, which in turn activates the N-terminal receiver stem to serve as platform for downstream partner recruitment
GV-sheaves, Fourier-Mukai transform, and generic vanishing
No full textWe use homological methods to establish a formal criterion for Generic Vanishing, in the sense originated by Green and Lazarsfeld and pursued further by Hacon and the first author, but in the context of an arbitrary Fourier-Mukai correspondence. For smooth projective varieties we apply this to deduce a Kodaira-type generic vanishing theorem for adjoint bundles of the form K_X + L with L a nef line bundle, and in fact a more general generic Nadel-type vanishing theorem for multiplier ideal sheaves. Still in the context of the Picard variety, the same method generates various other generic vanishing results, by reduction to standard vanishing theorems. We further use the formal criterion in order to address examples related to generic vanishing on higher rank moduli spaces (on curves and on some threefold Calabi-Yau fiber spaces)
Préjugés implicites et identités sociales multiples. Quelle pertinence pour l\u27éducation ?
No full textMaria Popa-Roch (maître de Conférences en science de l\u27éducation, IUFM Martinique) présente ses recherches expérimentales sur les préjugés implicites et les identités sociales multiples. Elle s\u27interroge sur les enjeux pédagogiques autour des activations automatiques et des catégorisations automatiques avec les évaluations des catégories et l?assignation de préjugés implicites
Activation and polar sequestration of PopA, a c-di-GMP effector protein involved in Caulobacter crescentus cell cycle control
No full textWhen Caulobacter crescentus enters S-phase the replication initiation inhibitor CtrA dynamically positions to the old cell pole to be degraded by the polar ClpXP protease. Polar delivery of CtrA requires PopA and the diguanylate cyclase PleD that positions to the same pole. Here we present evidence that PopA originated through gene duplication from its paralogue response regulator PleD and subsequent co-option as c-di-GMP effector protein. While the C-terminal catalytic domain (GGDEF) of PleD is activated by phosphorylation of the N-terminal receiver domain, functional adaptation has reversed signal transduction in PopA with the GGDEF domain adopting input function and the receiver domain serving as regulatory output. We show that the N-terminal receiver domain of PopA specifically interacts with RcdA, a component required for CtrA degradation. In contrast, the GGDEF domain serves to target PopA to the cell pole in response to c-di-GMP binding. In agreement with the divergent activation and targeting mechanisms, distinct markers sequester PleD and PopA to the old cell pole upon S-phase entry. Together these data indicate that PopA adopted a novel role as topology specificity factor to help recruit components of the CtrA degradation pathway to the protease specific old cell pole of C. crescentus
Power Converters, Electric Drives and Energy Storage Systems for Electrified Transportation and Smart Grid Applications
No full textThe proposed special issue (SI) has invited submissions related to renewable energy, energy storage, power converters and electric drive systems for electrified transportation and smart grid applications [...
IMPROVING SOCIAL MEDIA PRACTICES FOR B-TO-B MARKET
No full textB2B social networks are today at the heart of all discussions, whether at the professional or personal level. Indeed, there are more and more controversies around these tools of commu-nication. However, in many cases, social networks are a real advertising boost. Today, social networks in B2B are a real factor of influence and they are an integral part of a digital market-ing strategy.
An inductive research approach was applied in this thesis and a qualitative research method was used for collecting the data. The qualitative research was conducted through four inter-views, three of them with three different distributors for Kekkilä Professional and one inter-view with the marketing manager. The data was collected data from both primary and second-ary sources. Primary data was collected from the interviews and the secondary method in-cluded data collected from the author’s own experience, books and electric sources.
In the theoretical part, the author explains the meaning of digital marketing, social media mar-keting, which are the social media channels, and which social networks will be the most im-portant for Kekkilä Professional to focus on when the company will develop its social media practices for the B2B market in the future. The author continues with theories about particulari-ties for the B2B market. A SWOT analysis was created for the case company and a develop-ment plan for Kekkilä Professional is presented.
In conclusion, Kekkilä Professional should focus on social media channels (LinkedIn, Face-book and Twitter) in the future for the B2B market because using social media is essential in the digital communication era. However, it is important to take the time to design a complete social media strategy to use them wisely and to achieve the goals that Kekkilä Professional has set.
Social media has earned its acclaim in the B2B market and these channels became essential to explore, to generate traffic and to create leads
M-regularity and the fourier-mukai transform
No full textThis is a survey of M-regularity and its applications, expanding on lectures given by the second author at the Seattle conference, in August 2005, and at the Luminy workshop "Geometrie Algebrique Complexe", in October 2005
Taxonomic Study on Eleven Species from Mount Popa Area, Kyaukpadaung Township in Mandalay Region
No full textThe present research deals with floristic study of Mount Popa Area in Kyaukpadaung Township, Mandalay Region of Myanmar was undertaken since 2022. The total of 11 species under 11 genera belonging to 9 families were studied. The morphological characters of detailed taxonomic description of an individual species were described with their photographs. An artificial key to the studied species were also constructed. Among them, Butea monosperma (Lam.) Kunt, Chukrasia tabularis A. Juss, Indigofera tinchoria L., and Leea asiatica (L.) Ridsdale. were common species of the study area. In Mount Popa, Magnolia champaca (L.) Baill. ex Pierre. was the characteristic species of this area. Moreover, Leea asiatica (L.) Ridsdale., Chukrasia tabularis A. Juss, Martynia annua L. and Aeginetia indica L. were used as medicinal plants in the study area. Moreover, the near threatened species, critically endangered possibly extinct species, vulnerable species and endangered species were also recorded. In National Red List of Sri Lanka, Chukrasia tabularis A. Juss. is near threatened species, Aeginetia indica L. as critically endangered possibly extinct species, Butea monoaperma (Lam.) Kunt as vulnerable species and Abelmoschus ficulneus (L.) Wight & Arn. as near threatened and Pittosporum napaulense (D.C) Rehder & E.H Wilson are as endangered species. The floristic study of Mount Popa Area showed a relatively high diversity of wild plant species. For that reason, the study areas can be considered as important areas for the conservation of the floral diversity and it has been designated as Geopark recently
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