Kinesin-8 molecular motors: putting the brakes on chromosome oscillations

Recent studies suggest that the human Kinesin-8 molecular motor Kif18A has a role in chromosome congression. Specifically, these studies find that Kif18A promotes chromosome congression by attenuating chromosome oscillation magnitudes. Together with recent modeling work, in vitro studies, and the analysis of in vivo yeast data, these reports reveal how Kinesin-8 molecular motors might control chromosome oscillation amplitudes by spatially regulating the dynamic instability of microtubule plus-ends within the mitotic spindle

The microtubule-based motor Kar3 and plus end–binding protein Bim1 provide structural support for the anaphase spindle

In budding yeast, the mitotic spindle is comprised of 32 kinetochore microtubules (kMTs) and ∼8 interpolar MTs (ipMTs). Upon anaphase onset, kMTs shorten to the pole, whereas ipMTs increase in length. Overlapping MTs are responsible for the maintenance of spindle integrity during anaphase. To dissect the requirements for anaphase spindle stability, we introduced a conditionally functional dicentric chromosome into yeast. When centromeres from the same sister chromatid attach to opposite poles, anaphase spindle elongation is delayed and a DNA breakage-fusion-bridge cycle ensues that is dependent on DNA repair proteins. We find that cell survival after dicentric chromosome activation requires the MT-binding proteins Kar3p, Bim1p, and Ase1p. In their absence, anaphase spindles are prone to collapse and buckle in the presence of a dicentric chromosome. Our analysis reveals the importance of Bim1p in maintaining a stable ipMT overlap zone by promoting polymerization of ipMTs during anaphase, whereas Kar3p contributes to spindle stability by cross-linking spindle MTs

Rapid microtubule self-assembly kinetics

SUMMARY Microtubule assembly is vital for many fundamental cellular processes. Current models for microtubule assembly kinetics assume that the subunit dissociation rate from a microtubule tip is independent of free subunit concentration. Total-Internal-Reflection-Fluorescence (TIRF) microscopy experiments and data from a laser tweezers assay that measures in vitro microtubule assembly with nanometer resolution, provides evidence that the subunit dissociation rate from a microtubule tip increases as the free subunit concentration increases. These data are consistent with a two-dimensional model for microtubule assembly, and are explained by a shift in microtubule tip structure from a relatively blunt shape at low free concentrations to relatively tapered at high free concentrations. We find that because both the association and the dissociation rates increase at higher free subunit concentrations, the kinetics of microtubule assembly are an order-ofmagnitude higher than currently estimated in the literature

Translating a health behavior change intervention for delivery to 2-year college students: the importance of formative research

Young adults are at risk for weight gain in the transition to independent adulthood; 2-year college students are at greater risk and understudied relative to 4-year students. This project conducted formative research for a randomized controlled weight gain prevention trial among 2-year college students, to ensure appropriateness of content and delivery of a curriculum originally developed for 4-year college students. Data were collected from community college students, faculty, and staff from October 2009 to August 2011. Work included focus groups and key informant interviews, curriculum pilot testing, and social network and support website beta testing. Based on focus groups and interviews, program content, course delivery modes, and communication channels were adjusted to meet population interests and preferences. The course was delivered successfully in pilot testing, and the website was received well by beta testers. Formative work successfully guided program adaptations to address population needs

Model Convolution: A Computational Approach to Digital Image Interpretation

Digital fluorescence microscopy is commonly used to track individual proteins and their dynamics in living cells. However, extracting molecule-specific information from fluorescence images is often limited by the noise and blur intrinsic to the cell and the imaging system. Here we discuss a method called “model-convolution,” which uses experimentally measured noise and blur to simulate the process of imaging fluorescent proteins whose spatial distribution cannot be resolved. We then compare model-convolution to the more standard approach of experimental deconvolution. In some circumstances, standard experimental deconvolution approaches fail to yield the correct underlying fluorophore distribution. In these situations, model-convolution removes the uncertainty associated with deconvolution and therefore allows direct statistical comparison of experimental and theoretical data. Thus, if there are structural constraints on molecular organization, the model-convolution method better utilizes information gathered via fluorescence microscopy, and naturally integrates experiment and theory

Weight and Weight-Related Behaviors Among 2-Year College Students

The purpose of this paper is to describe weight indicators and weight-related behaviors of students enrolled in 2-year colleges, including sex differences

Islands Containing Slowly Hydrolyzable GTP Analogs Promote Microtubule Rescues

Microtubules are dynamic polymers of GTP- and GDP-tubulin that undergo stochastic transitions between growing and shrinking phases. Rescues, the conversion from shrinking to growing, have recently been proposed to be to the result of regrowth at GTP-tubulin islands within the lattice of growing microtubules. By introducing mixed GTP/GDP/GMPCPP (GXP) regions within the lattice of dynamic microtubules, we reconstituted GXP islands in vitro (GMPCPP is the slowly hydrolyzable GTP analog guanosine-5′-[(α,β)-methyleno]triphosphate). We found that such islands could reproducibly induce rescues and that the probability of rescue correlated with both the size of the island and the percentage of GMPCPP-tubulin within the island. The islands slowed the depolymerization rate of shortening microtubules and promoted regrowth more readily than GMPCPP seeds. Together, these findings provide new mechanistic insights supporting the possibility that rescues could be triggered by enriched GTP-tubulin regions and present a new tool for studying such rescue events in vitro

Erratum to: Model Convolution: A Computational Approach to Digital Image Interpretation

Digital fluorescence microscopy is commonly used to track individual proteins and their dynamics in living cells. However, extracting molecule-specific information from fluorescence images is often limited by the noise and blur intrinsic to the cell and the imaging system. Here we discuss a method called “model-convolution,” which uses experimentally measured noise and blur to simulate the process of imaging fluorescent proteins whose spatial distribution cannot be resolved. We then compare model-convolution to the more standard approach of experimental deconvolution. In some circumstances, standard experimental deconvolution approaches fail to yield the correct underlying fluorophore distribution. In these situations, model-convolution removes the uncertainty associated with deconvolution and therefore allows direct statistical comparison of experimental and theoretical data. Thus, if there are structural constraints on molecular organization, the model-convolution method better utilizes information gathered via fluorescence microscopy, and naturally integrates experiment and theory

Racial Differences in the Association Between Luminal Master Regulator Gene Expression Levels and Breast Cancer Survival

Compared with their European American (EA) counterparts, African American (AA) women are more likely to die from breast cancer in the United States. This disparity is greatest in hormone receptor-positive subtypes. Here we uncover biological factors underlying this disparity by comparing functional expression and prognostic significance of master transcriptional regulators of luminal differentiation.Fil: Byun, Jung S.. National Institutes of Health; Estados UnidosFil: Singhal, Sandeep K.. Columbia University; Estados UnidosFil: Park, Samson. National Institutes of Health; Estados UnidosFil: Yi, Dae Ik. National Institutes of Health; Estados UnidosFil: Yan, Tingfen. National Institutes of Health; Estados UnidosFil: Caban, Ambar. Columbia University Medical Center; Estados UnidosFil: Jones, Alana. National Institutes of Health; Estados UnidosFil: Mukhopadhyay, Partha. Columbia University Medical Center; Estados UnidosFil: Gille, Sarah. National Institutes of Health; Estados UnidosFil: Hewitt, Stephen M.. No especifíca;Fil: Newman, Lisa. No especifíca;Fil: Davis, Melissa B.. Henry Ford Health System; Estados UnidosFil: Jenkins, Brittany D.. Henry Ford Health System; Estados UnidosFil: Sepulveda, Jorge L.. Columbia University Medical Center; Estados UnidosFil: de Siervi, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Nápoles, Anna María. National Institute On Minority Health And Health Disparities; Estados UnidosFil: Vohra, Nasreen A.. East Carolina University; Estados UnidosFil: Gardner, Kevin. Columbia University Medical Center; Estados Unido

Protein expression of the gp78 E3 ligase predicts poor breast cancer outcome based on race

Women of African ancestry suffer higher rates of breast cancer mortality compared with all other groups in the United States. Though the precise reasons for these disparities remain unclear, many recent studies have implicated a role for differences in tumor biology. Using an epitope-validated antibody against the endoplasmic reticulum-associated E3 ligase, gp78, we show that elevated levels of gp78 in patient breast cancer cells predict poor survival. Moreover, high levels of gp78 are associated with poor outcomes in both ER+ and ER- tumors, and breast cancers expressing elevated amounts of gp78 protein are enriched in gene expression pathways that influence cell cycle, metabolism, receptor-mediated signaling, and cell stress response pathways. In multivariate analysis adjusted for subtype and grade, gp78 protein is an independent predictor of poor outcomes in women of African ancestry. Furthermore, gene expression signatures, derived from patients stratified by gp78 protein expression, are strong predictors of recurrence and pathological complete response in retrospective clinical trial data and share many common features with gene sets previously identified to be overrepresented in breast cancers based on race. These findings implicate a prominent role for gp78 in tumor progression and offer insights into our understanding of racial differences in breast cancer outcomes.Fil: Singhal, Sandeep K.. No especifíca;Fil: Byun, Jung S.. National Institutes of Health; Estados UnidosFil: Yan, Tingfen. National Institutes of Health; Estados UnidosFil: Yancey, Ryan. Columbia University; Estados UnidosFil: Caban, Ambar. Columbia University; Estados UnidosFil: Hernandez, Sara Gil. National Institutes of Health; Estados UnidosFil: Bufford, Sediqua. No especifíca;Fil: Hewitt, Stephen M.. No especifíca;Fil: Winfield, Joy. Columbia University; Estados UnidosFil: Pradhan, Jaya. Columbia University; Estados UnidosFil: Mustkov, Vesco. Columbia University; Estados UnidosFil: McDonald, Jasmine A.. No especifíca;Fil: Pérez Stable, Eliseo J.. National Institutes of Health; Estados UnidosFil: Nápoles, Anna María. National Institutes of Health; Estados UnidosFil: Vohra, Nasreen. No especifíca;Fil: de Siervi, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Yates, Clayton. No especifíca;Fil: Davis, Melissa B.. No especifíca;Fil: Yang, Mei. No especifíca;Fil: Tsai, Yien Che. No especifíca;Fil: Weissman, Allan M.. No especifíca;Fil: Gardner, Kevin. Columbia University; Estados Unido