RESUMEN
While research in youth mentoring is extensive in the U.S., little research has explored its effectiveness in New Zealand, despite its growth in the past 20 years. While arguments have been raised that overseas models may not fit all cultural contexts within New Zealand, there appears to be limited evidence supporting this contention. Further, little is known about associations between effectiveness and the cultural appropriateness of programs and research. This systematic review of youth mentoring programs in New Zealand is based on 26 studies that met inclusion criteria. Of those, 14 had a significant proportion (15% or more) of indigenous Maori youth and six had a significant proportion of Pasifika (Pacific Islander) youth. While almost all programs and associated research were culturally appropriate to the overall New Zealand context, they tended to be less culturally appropriate for programs working with Maori and Pasifika youth. Further, there was a negative association between cultural appropriateness and program effectiveness.
Asunto(s)
Cultura , Mentores , Etnicidad , Humanos , Nueva ZelandaRESUMEN
In budding yeast, the essential roles of microtubules include segregating chromosomes and positioning the nucleus during mitosis. Defects in these functions can lead to aneuploidy and cell death. To ensure proper mitotic spindle and cytoplasmic microtubule formation, the cell must maintain appropriate stoichiometries of alpha- and beta-tubulin, the basic subunits of microtubules. The experiments described here investigate the minimal levels of tubulin heterodimers needed for mitotic function. We have found a triple-mutant strain, pac10Delta plp1Delta yap4Delta, which has only 20% of wild-type tubulin heterodimer levels due to synthesis and folding defects. The anaphase spindles in these cells are approximately 64% the length of wild-type spindles. The mutant cells are viable and accurately segregate chromosomes in mitosis, but they do have specific defects in mitosis such as abnormal nuclear positioning. The results establish that cells with 20% of wild-type levels of tubulin heterodimers can perform essential cellular functions with a short spindle, but require higher tubulin heterodimer concentrations to attain normal spindle length and prevent mitotic defects.
Asunto(s)
Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/citología , Saccharomyces cerevisiae/metabolismo , Tubulina (Proteína)/química , Tubulina (Proteína)/metabolismo , Proteínas Adaptadoras Transductoras de Señales , Secuencia de Bases , Segregación Cromosómica , Cromosomas Fúngicos/genética , ADN de Hongos/genética , Genes Fúngicos , Lipoproteínas/genética , Lipoproteínas/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Mitosis/genética , Mutación , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fenotipo , Pliegue de Proteína , Estructura Cuaternaria de Proteína , ARN de Hongos/genética , ARN de Hongos/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Huso Acromático/ultraestructura , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Tubulina (Proteína)/genéticaRESUMEN
Undimerized beta-tubulin is toxic in the yeast S. cerevisiae. It can arise if levels of beta-tubulin and alpha-tubulin are unbalanced or if the tubulin heterodimer dissociates. We are using the toxicity of beta-tubulin to understand early steps in microtubule morphogenesis. We find that deletion of PLP1 suppresses toxic beta-tubulin formed by disparate levels of alpha- and beta-tubulin. That suppression occurs either when alpha-tubulin is modestly underexpressed relative to beta-tubulin or when beta-tubulin is inducibly and strongly overexpressed. Plp1p does not affect tubulin expression. Instead, a significant proportion of the undimerized beta-tubulin in plp1Delta cells is less toxic than that in wild-type cells. It is also less able to combine with alpha-tubulin to form a heterodimer. As a result, plp1Delta cells have lower levels of heterodimer. Importantly, plp1Delta cells that also lack Pac10, a component of the GimC/PFD complex, are even less affected by free beta-tubulin. Our results suggest that Plp1p defines a novel early step in beta-tubulin folding.
Asunto(s)
Pliegue de Proteína , Saccharomyces cerevisiae/metabolismo , Tubulina (Proteína)/metabolismo , Ubiquitina-Proteína Ligasas , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Chaperonina 60/metabolismo , Dimerización , Proteínas F-Box , Eliminación de Gen , Lipoproteínas/genética , Lipoproteínas/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Proteínas Asociadas a Microtúbulos/genética , Proteínas Asociadas a Microtúbulos/metabolismo , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Tubulina (Proteína)/genética , Tubulina (Proteína)/toxicidadRESUMEN
Cells expressing a mutant allele of alpha-tubulin, tub1-729, are cold sensitive and arrest as large-budded cells with microtubule defects. The cold sensitivity of tub1-729 is suppressed by extra copies of a subset of the mitotic checkpoint genes BUB1, BUB3, and MPS1, but not MAD1, MAD2, and MAD3. This suppression by checkpoint genes does not depend upon their role in the MAD2-dependent spindle assembly checkpoint. In addition, BUB1 requires an intact kinase domain as well as Bub3p to suppress tub1-729. The data suggest that tub1-729 cells are defective in microtubule-kinetochore attachments and that the products of specific checkpoint genes can act either directly or indirectly to affect these attachments.
Asunto(s)
Saccharomyces cerevisiae/genética , Huso Acromático/genética , Tubulina (Proteína)/genética , Alelos , Secuencia de Bases , Cromosomas Fúngicos/genética , Cartilla de ADN , Genes Fúngicos , Genotipo , Mitosis/genética , Plásmidos , Reacción en Cadena de la Polimerasa , Saccharomyces cerevisiae/citología , Saccharomyces cerevisiae/crecimiento & desarrollo , TemperaturaRESUMEN
Kinetochore components have catalytic as well as structural activities. New evidence illustrates how these proteins integrate spindle morphogenesis with regulation of the timing and accuracy of chromosome segregation.
Asunto(s)
Cinetocoros/fisiología , Mitosis/fisiología , Huso Acromático/fisiología , Anafase/fisiología , Animales , Segregación Cromosómica/fisiología , Humanos , Sustancias Macromoleculares , Microtúbulos/fisiologíaRESUMEN
Free beta-tubulin not in heterodimers with alpha-tubulin can be toxic, disrupting microtubule assembly and function. We are interested in the mechanisms by which cells protect themselves from free beta-tubulin. This study focused specifically on the function of Rbl2p, which, like alpha-tubulin, can rescue cells from free beta-tubulin. In vitro studies of the mammalian homolog of Rbl2p, cofactor A, have suggested that Rbl2p/cofactor A may be involved in tubulin folding. Here we show that Rbl2p becomes essential in cells containing a modest excess of beta-tubulin relative to alpha-tubulin. However, this essential activity of Rbl2p/cofactorA does not depend upon the reactions described by the in vitro assay. Rescue of beta-tubulin toxicity requires a minimal but substoichiometric ratio of Rbl2p to beta-tubulin. The data suggest that Rbl2p binds transiently to free beta-tubulin, which then passes into an aggregated form that is not toxic.