Regulating repression : roles for the Sir4 N-terminus in linker DNA protection and stabilization of epigenetic states

The Gasser laboratory is supported by the Novartis Research Foundation and the EU training network Nucleosome 4D. SK was supported by an EMBO long-term fellowship, a Schrodinger fellowship from the FWF, and the Swiss SystemsX.ch initiative/C-CINA; HCF by an EMBO long-term fellowship.Silent information regulator proteins Sir2, Sir3, and Sir4 form a heterotrimeric complex that represses transcription at subtelomeric regions and homothallic mating type (HM) loci in budding yeast. We have performed a detailed biochemical and genetic analysis of the largest Sir protein, Sir4. The N-terminal half of Sir4 is dispensable for SIR-mediated repression of HM loci in vivo, except in strains that lack Yku70 or have weak silencer elements. For HM silencing in these cells, the C-terminal domain (Sir4C, residues 747-1,358) must be complemented with an N-terminal domain (Sir4N; residues 1-270), expressed either independently or as a fusion with Sir4C. Nonetheless, recombinant Sir4C can form a complex with Sir2 and Sir3 in vitro, is catalytically active, and has sedimentation properties similar to a full-length Sir4-containing SIR complex. Sir4C-containing SIR complexes bind nucleosomal arrays and protect linker DNA from nucleolytic digestion, but less effectively than wild-type SIR complexes. Consistently, full-length Sir4 is required for the complete repression of subtelomeric genes. Supporting the notion that the Sir4 N-terminus is a regulatory domain, we find it extensively phosphorylated on cyclin-dependent kinase consensus sites, some being hyperphosphorylated during mitosis. Mutation of two major phosphoacceptor sites (S63 and S84) derepresses natural subtelomeric genes when combined with a serendipitous mutation (P2A), which alone can enhance the stability of either the repressed or active state. The triple mutation confers resistance to rapamycin-induced stress and a loss of subtelomeric repression. We conclude that the Sir4 N-terminus plays two roles in SIR-mediated silencing: it contributes to epigenetic repression by stabilizing the SIR-mediated protection of linker DNA; and, as a target of phosphorylation, it can destabilize silencing in a regulated manner.Publisher PDFPeer reviewe

Was the M_w 7.5 1952 Kern County, California, earthquake induced (or triggered)?

Several recent studies have presented evidence that significant induced earthquakes occurred in a number of oil-producing regions during the early and mid-twentieth century related to either production or wastewater injection. We consider whether the 21 July 1952 M_w 7.5 Kern County earthquake might have been induced by production in the Wheeler Ridge oil field. The mainshock, which was not preceded by any significant foreshocks, occurred 98 days after the initial production of oil in Eocene strata at depths reaching 3 km, within ~1 km of the White Wolf fault (WWF). Based on this spatial and temporal proximity, we explore a potential causal relationship between the earthquake and oil production. While production would have normally be expected to have reduced pore pressure, inhibiting failure on the WWF, we present an analytical model based on industry stratigraphic data and best estimates of parameters whereby an impermeable splay fault adjacent to the main WWF could plausibly have blocked direct pore pressure effects, allowing the poroelastic stress change associated with production to destabilize the WWF, promoting initial failure. This proof-of-concept model can also account for the 98-day delay between the onset of production and the earthquake. While the earthquake clearly released stored tectonic stress, any initial perturbation on or near a major fault system can trigger a larger rupture. Our proposed mechanism provides an explanation for why significant earthquakes are not commonly induced by production in proximity to major faults

Amino acid substitutions within the heptad repeat domain 1 of murine coronavirus spike protein restrict viral antigen spread in the central nervous system.

Targeted recombination was carried out to select mouse hepatitis viruses (MHVs) in a defined genetic background, containing an MHV-JHM spike gene encoding either three heptad repeat 1 (HR1) substitutions (Q1067H, Q1094H, and L1114R) or L1114R alone. The recombinant virus, which expresses spike with the three substitutions, was nonfusogenic at neutral pH. Its replication was significantly inhibited by lysosomotropic agents, and it was highly neuroattenuated in vivo. In contrast, the recombinant expressing spike with L1114R alone mediated cell-to-cell fusion at neutral pH and replicated efficiently despite the presence of lysosomotropic agents; however, it still caused only subclinical morbidity and no mortality in animals. Thus, both recombinant viruses were highly attenuated and expressed viral antigen which was restricted to the olfactory bulbs and was markedly absent from other regions of the brains at 5 days postinfection. These data demonstrate that amino acid substitutions, in particular L1114R, within HR1 of the JHM spike reduced the ability of MHV to spread in the central nervous system. Furthermore, the requirements for low pH for fusion and viral entry are not prerequisites for the highly attenuated phenotype

Forebrain-specific deletion of Cdk5 in pyramidal neurons results in mania-like behavior and cognitive impairment

Cyclin-dependent kinase 5 (Cdk5) is associated with synaptic plasticity and cognitive function. Previous reports have demonstrated that Cdk5 is necessary for memory formation, although others have reported Cdk5 conditional knockout mouse models exhibiting enhanced learning and memory. Furthermore, how Cdk5 acts in specific cell populations to affect behavior and cognitive outcomes remains unclear. Here we conduct a behavioral characterization of a forebrain-specific Cdk5 conditional knockout mouse model under the αCaMKII promoter, in which Cdk5 is ablated in excitatory pyramidal neurons of the forebrain. The Cdk5 conditional knockouts exhibit hyperactivity in the open field, reduced anxiety, and reduced behavioral despair. Moreover, the Cdk5 conditional knockouts also display impaired spatial learning in the Morris water maze and are severely impaired in contextual fear memory, which correspond to deficits in synaptic transmission. Remarkably, the hyperactivity of the Cdk5 conditional knockouts can be ameliorated by the administration of lithium chloride, an inhibitor of GSK3β signaling. Collectively, our data reveal that Cdk5 ablation from forebrain excitatory neurons results in deleterious effects on emotional and cognitive behavior and highlight a key role for Cdk5 in regulating the GSK3β signaling pathway.National Institutes of Health (U.S.) (Grant T32 MH074249)National Institutes of Health (U.S.) (Grant R01 NS051874

Propuesta de mejora del servicio de crédito aplicando la metodología Lean Service en la Cooperativa de Ahorro y Crédito Fondesurco

La presente investigación busca determinar la incidencia de la metodología Lean service en el servicio de crédito de la Cooperativa de ahorro y crédito Fondesurco. Para ello se hace uso de las herramientas del Lean, como el ordenamiento de las 5s y las tarjetas Kanban. La problemática de la presente investigación está relacionado a la falta de organización, formatos con datos incompletos, expedientes desordenados, manejo de formatos, demoras en la realización de trabajo, falta de coordinación en las visitas y la falta de capacitación y entrenamiento. Todo ello esta englobado en: Materiales, Medio ambiente y Método. La identificación de la problemática se hizo en base al análisis 6M y Pareto. La metodología aplicada es descriptiva, no experimenta, y de enfoque cuantitativo. Respecto a la recolección de datos, se aplicó la observación de los procesos y la encuesta al personal de la cooperativa que participa en el proceso de crédito. Además se aplica los pasos de la metodología Lean service para las herramientas de 5s y kanban. El procesamiento de los datos se realizó aplicando el programa de Bizagi Modeler para el proceso de crédito, con las especificaciones de tiempo para cada actividad. Obteniendo como resultado que la propuesta de implementación de la metodología Lean service, permite mejorar el servicio de crédito en la Cooperativa de ahorro y crédito Fondesurco, en un 17% respecto a los tiempos manejados para cada proceso, además permite la reducción del tiempo de espera del cliente en un 68%. Además permite un mejor orden y limpieza para el desarrollo de las actividades y manejo de formato, trazabilidad en los documentos, reducción de tiempo de las actividades, reducción del tiempo de espera del cliente.TesisCampus Arequip

Modulation of drug sensitivity in yeast cells by the ATP‐binding domain of human DNA topoisomerase IIα

Epipodophyllotoxins are effective antitumour drugs that trap eukaryotic DNA topoisomerase II in a covalent complex with DNA. Based on DNA cleavage assays, the mode of interaction of these drugs was proposed to involve amino acid residues of the catalytic site. An in vitro binding study, however, revealed two potential binding sites for etoposide within human DNA topoisomerase IIα (htopoIIα), one in the catalytic core of the enzyme and one in the ATP‐binding N‐terminal domain. Here we have tested how N‐terminal mutations that reduce the affinity of the site for etoposide or ATP affect the sensitivity of yeast cells to etoposide. Surprisingly, when introduced into full‐length enzymes, mutations that lower the drug binding capacity of the N‐terminal domain in vitro render yeast more sensitive to epipodophyllotoxins. Consistently, when the htopoIIα N‐terminal domain alone is overexpressed in the presence of yeast topoII, cells become more resistant to etoposide. Point mutations that weaken etoposide binding eliminate this resistance phenotype. We argue that the N‐terminal ATP‐binding pocket competes with the active site of the holoenzyme for binding etoposide both in cis and in trans with different outcomes, suggesting that each topoisomerase II monomer has two non‐equivalent drug‐binding site

Piloting a Savings-Led Microfinance Intervention with Women Engaging in Sex Work in Mongolia: Further Innovation for HIV Risk Reduction

This paper describes a pilot study testing the feasibility of an innovative savings-led microfinance intervention in increasing the economic empowerment and reducing the sexual risk behavior of women engaging in sex work in Mongolia. Women’s economic vulnerability may increase their risk for HIV by compromising their ability to negotiate safer sex with partners and heightening the likelihood they will exchange sex for survival. Microfinance has been considered a potentially powerful structural HIV prevention strategy with women conducting sex work, as diversification of income sources may increase women’s capacity to negotiate safer transactional sex. With 50% of all reported female HIV cases in Mongolia detected among women engaging in sex work, direct prevention intervention with women conducting sex work represents an opportunity to prevent a potentially rapid increase in HIV infection in urban Mongolia. The piloted intervention consisted of a matched savings program in which matched savings could be used for business development or vocational education, combined with financial literacy and business development training for women engaging in sex work. Results of the pilot demonstrate participants’ increased confidence in their ability to manage finances, greater hope for pursuing vocational goals, moderate knowledge gains regarding financial literacy, and an initial transition from sex work to alternative income generation for five out of nine participants. The pilot findings highlight the potential for such an intervention and the need for a clinical trial testing the efficacy of savings-led microfinance programs in reducing HIV risk for women engaging in sex work in Mongolia

Print versus screen—presentation medium-dependent picture consumption

Part I: The use of digital technologies has forever changed how consumers are capturing, sharing, and storing their pictures. The long-term objective of Part I of this study is to obtain an overall picture of the current state of consumer photographers’ practices. While digital camera owners are taking more photos than ever before, most are not printing them. However, experiments conducted on the presentation mediumdependent differences in picture consumption showed that a majority of the participants prefer printed images to images viewed on a screen. Regardless of this preference, participants did not print images very often for a variety of reasons, including lack of time or money. In addition, results showed that the most commonly used printing tools included Kodak EasyShare Gallery, Shutterfly, and Flickr. Finally, participants cited Photoshop, Lightroom, and Picasa as the primary editing tools, with Facebook being mentioned as the main sharing tool. Parts II & III: The advent of digital print engines capable of achieving high image quality has opened up many new and exciting print product opportunities, including the short-run printing of magazines. However, content available for magazines is also readily available on-line. It is not immediately obvious that the capability of creating a short-run magazine translates into a viable business model; just because they can be printed does not necessarily mean that it makes sense to do so. The objective of this project was to take the first steps toward identifying and understanding the differences in how information is consumed from print on paper versus computer display and which characteristics of these media are particularly relevant in this comparison. Longer-term, it is intended to explore how such differences affect the efficacy of magazine advertising. This evaluation involved an assessment of differences for several metrics, including information retention, time taken to view images, preference for visually consuming information, and distribution of visual gaze as measured by eyetrackers. Experimentation was conducted that focused on the first three of these four factors (Part II). Experimentation in Part III generally confirmed the results of this study: specifically, that people preferred the hard copy rendition over a PDF when given the choice (for reasons of image accessibility and tangibility), and that neither the time used to view the photo books nor information retention as measured by image recognition and information recall were affected by the medium in which the photo book was seen. The results of this study also agreed with earlier research findings that observers tend to fixate first and most often in the central areas of images. This research also found, however, important differences between how the observers viewed the printed and screen versions of the photo book, with the screen group having more fixations per image for many of the images early in the book (though not spending more time with these images), while the print group switched more often between images. While the work conducted in Part II suggested that there were no important differences between the print and screen groups of observers, the results of Part III hint at differences that may be important with regard to individual images or image layouts. Further work involving image content with a more balanced mix of text and pictorial imagery might prove useful in exploring these findings further