Modulation of sterol homeostasis by the Cdc42p effectors Cla4p and Ste20p in the yeast Saccharomyces cerevisiae

This article is available open access through the publisher’s website at the link below. Copyright @ 2009 The Authors.The conserved Rho-type GTPase Cdc42p is a key regulator of signal transduction and polarity in eukaryotic cells. In the yeast Saccharomyces cerevisiae, Cdc42p promotes polarized growth through the p21-activated kinases Ste20p and Cla4p. Previously, we demonstrated that Ste20p forms a complex with Erg4p, Cbr1p and Ncp1p, which all catalyze important steps in sterol biosynthesis. CLA4 interacts genetically with ERG4 and NCP1. Furthermore, Erg4p, Ncp1p and Cbr1p play important roles in cell polarization during vegetative growth, mating and filamentation. As Ste20p and Cla4p are involved in these processes it seems likely that sterol biosynthetic enzymes and p21-activated kinases act in related pathways. Here, we demonstrate that the deletion of either STE20 or CLA4 results in increased levels of sterols. In addition, higher concentrations of steryl esters, the storage form of sterols, were observed in cla4Δ cells. CLA4 expression from a multicopy plasmid reduces enzyme activity of Are2p, the major steryl ester synthase, under aerobic conditions. Altogether, our data suggest that Ste20p and Cla4p may function as negative modulators of sterol biosynthesis. Moreover, Cla4p has a negative effect on steryl ester formation. As sterol homeostasis is crucial for cell polarization, Ste20p and Cla4p may regulate cell polarity in part through the modulation of sterol homeostasis.Deutsche Forschungsgemeinschaft and the Austrian FWF

Sensitivity to the KARMEN Timing Anomaly at MiniBooNE

We present sensitivities for the MiniBooNE experiment to a rare exotic pion decay producing a massive particle, Q^0. This type of decay represents one possible explanation for the timing anomaly reported by the KARMEN collaboration. MiniBooNE will be able to explore an area of the KARMEN signal that has not yet been investigated

Searching for Sakitawak: Place and People in Northern Saskatchewan\u27s Île-à-la-Crosse

This presentation is a history of a small community, Île-à-la-Crosse, located in an area now part of Saskatchewan, Canada. With an historic reputation for cooperation and enviable trading circumstances, its residents traditionally have determined that protection of the community ensured the best opportunities for the advancement and security of individuals. As a result of this belief, residents reinforced their own understandings of sustainability as a means to ensure personal success. The community’s fame for hosting such a set of norms grew, particularly from the eighteenth to the twentieth century, and outsiders often visited to improve their own efforts as a result of this reputation. Given the belief that community longevity assured individual concerns, many visitors quickly decided to adopt local processes even if those functions contrasted sharply from their own original beliefs. Based on these decisions, the visitors’ institutions experienced changes as well. Through this social cooperation to better ensure personal success, a culture began to develop, and so the village’s distinctive administrative and economic processes were continued through family and neighbourly ties. Some characteristics, such as multiculturalism, shared land use, complex trading activities, and sustainability, further distinguished Île-à-la-Crosse as a result. Though well aware of the village a number of parties (such as the Hudson’s Bay Company and the Canadian government), still regularly excluded the community from their deliberations because of its unique ability to supposedly need less intervention considered necessary elsewhere. These various corporate and political authorities, concerned with their own existence, instead emphasised the conditions of communities that demonstrated social hostility, monetary difficulties, and other forms of disparity. As these historic parties failing to appreciate the village’s positive components in their fullest form, historians also did not integrate the village into their narratives since they almost always focused on conflict and change in their investigations. Because of this missing analysis about Île-à-la-Crosse, historical accounts have created lacunae in our understanding and awareness not just of local but also of provincial and national issues pertaining to “development.” Today, the lack of historic and historical awareness has as well directly impacted a modern day Indigenous “land claim”. Particularly when examining “absence” and “overlap” in a space’s natural and social form, Île-à-la-Crosse’s story from its earliest existence to its present shape can finally remind us how local conditions –even before humans started living in those circumstances – can teach us about how to survive and succeed today as individuals and as part of a larger community and country. It also reminds us how we should pay more attention to peace, cooperation and interaction in both intellectual and social circles

The Heavy-Flavour Contribution to Proton Structure

We present theoretical and experimental considerations pertaining to deeply inelastic heavy-flavour production at HERA. The various theoretical uncertainties in the cross section calculation are discussed. Cuts are imposed to determine the fraction of charm production accessible to the detectors. The production of charm at asymptotic $Q^2$ and bottom production are also covered. Experimental aspects include current charm production data analysis and prospects for future analyses including anticipated high precision and distinguishing photon-gluon fusion charm events from excitation from the charm parton density. The feasibility of measuring $F_2^{b\overline b}(x,Q^2)$ is investigated.Comment: 22 total pages with 16 figures. To appear in abbreviated form in the proceedings of the workshop ``Future Physics at HERA'', DESY, Hamburg, 199

Search for Exotic Muon Decays

Recently, it has been proposed that the observed anomaly in the time distribution of neutrino induced reactions, reported by the KARMEN collaboration, can be interpreted as a signal from an exotic muon decay branch mu+ to e+ X. It has been shown that this hypothesis gives an acceptable fit to the KARMEN data if the boson X has a mass of m_X=103.9MeV/c^2, close to the kinematical limit. We have performed a search for the X particle by studying for the first time the very low energy part of the Michel spectrum in mu+ decays. Using a HPGe detector setup at the muE4 beamline at PSI we find branching ratios BR(mu+ to e+ X)<5.7e-4 (90% C.L.) for most of the region 103MeV/c^2<m_X<105MeV/c^2.Comment: 9 page

The reaction np→ppπ−{n} {p} \to {p} {p} \pi^{-} from threshold up to 570 MeV

The reaction ${n} {p} \to {p} {p} \pi^{-}$ has been studied in a kinematically complete measurement with a large acceptance time-of-flight spectrometer for incident neutron energies between threshold and 570 MeV. The proton-proton invariant mass distributions show a strong enhancement due to the pp($^{1}{S}_{0}$) final state interaction. A large anisotropy was found in the pion angular distributions in contrast to the reaction ${p}{p} \to {p}{p} \pi^{0}$. At small energies, a large forward/backward asymmetry has been observed. From the measured integrated cross section $\sigma({n}{p} \to {\rm p}{p} \pi^{-})$, the isoscalar cross section $\sigma_{01}$ has been extracted. Its energy dependence indicates that mainly partial waves with Sp final states contribute. Note: Due to a coding error, the differential cross sections ${d \sigma}/{d M_{pp}}$ as shown in Fig. 9 are too small by a factor of two, and inn Table 3 the differential cross sections ${d \sigma}/{d \Omega_{\pi}^{*}}$ are too large by a factor of $10/2\pi$. The integrated cross sections and all conclusions remain unchanged. A corresponding erratum has been submitted and accepted by European Physics Journal.Comment: 18 pages, 16 figure