Life Sciences Commons^™

Drosophila Fascin Mutants Are Rescued By Overexpression Of The Villin-Like Protein, Quail, Kelly Cant, Brenda A. Knowles, Shalina Mahajan-Miklos, Matthew Heintzelman, Lynn Cooley

Dartmouth Scholarship

Actin bundle assembly in specialized structures such as microvilli on intestinal epithelia and Drosophila bristles requires two actin bundling proteins. In these systems, the distinct biochemical properties and temporal localization of actin bundling proteins suggest that these proteins are not redundant. During Drosophila oogenesis, the formation of cytoplasmic actin bundles in nurse cells requires two actin bundling proteins, fascin encoded by the singed gene and a villin-like protein encoded by the quail gene. singed and quail mutations are fully recessive and each mutation disrupts nurse cell cytoplasmic actin bundle formation. We used P-element mediated germline transformation to overexpress quail in …

The Leukemic Protein Core Binding Factor Beta (Cbfbeta)-Smooth-Muscle Myosin Heavy Chain Sequesters Cbfalpha2 Into Cytoskeletal Filaments And Aggregates, Neeraj Adya, Terryl Stacy, Nancy A. Speck, Pu Paul Liu

Dartmouth Scholarship

The fusion gene CBFB-MYH11 is generated by the chromosome 16 inversion associated with acute myeloid leukemias. This gene encodes a chimeric protein involving the core binding factor β (CBFβ) and the smooth-muscle myosin heavy chain (SMMHC). Mouse model studies suggest that this chimeric protein CBFβ-SMMHC dominantly suppresses the function of CBF, a heterodimeric transcription factor composed of DNA binding subunits (CBFα1 to 3) and a non-DNA binding subunit (CBFβ). This dominant suppression results in the blockage of hematopoiesis in mice and presumably contributes to leukemogenesis. We used transient-transfection assays, in combination with immunofluorescence and green fluorescent protein-tagged proteins, to monitor …

Identification And Characterization Of Spcu, A Chaperone Required For Efficient Secretion Of The Exou Cytotoxin, Viviane Finck-Barbançon, Timothy L. Yahr, Dara W. Frank

Dartmouth Scholarship

In recent studies, we have shown that Pseudomonas aeruginosa strains that are acutely cytotoxic in vitro damage the lung epithelium in vivo. Genetic analysis indicated that the factor responsible for acute cytotoxicity was controlled by ExsA and therefore was part of the exoenzyme S regulon. The specific virulence determinant responsible for epithelial damage in vivo and cytotoxicity in vitro was subsequently mapped to the exoU locus. The present studies are focused on a genetic characterization of the exoU locus. Northern blot analyses and complementation experiments indicated that a region downstream of exoU was expressed and that the expression of this …

The Seca Subunit Of Escherichia Coli Preprotein Translocase Is Exposed To The Periplasm, Jerry Eichler, William Wickner

Dartmouth Scholarship

SecA undergoes conformational changes during translocation, inserting domains into and across the membrane or enhancing the protease resistance of these domains. We now show that some SecA bound at SecYEG is accessible from the periplasm to a membrane-impermeant probe in cells with a permeabilized outer membrane but an intact plasma membrane.

Transport Of Er Vesicles On Actin Filaments In Neurons By Myosin V, Joel S. Tabb, Bradley J. Molyneaux, Darien L. Cohen, Sergei A. Kuznetsov, George M. Langford

Dartmouth Scholarship

Axoplasmic organelles in the giant axon of the squid have been shown to move on both actin filaments and microtubules and to switch between actin filaments and microtubules during fast axonal transport. The objectives of this investigation were to identify the specific classes of axoplasmic organelles that move on actin filaments and the myosin motors involved. We developed a procedure to isolate endoplasmic reticulum (ER) from extruded axoplasm and to reconstitute its movement in vitro. The isolated ER vesicles moved on exogenous actin filaments adsorbed to coverslips in an ATP-dependent manner without the addition of soluble factors. Therefore myosin was …

Transport Of Axl2p Depends On Erv14p, An Er–Vesicle Protein Related To The Drosophila Cornichon Gene Product, Jacqueline Powers, Charles Barlowe

Dartmouth Scholarship

COPII-coated ER-derived transport vesicles from Saccharomyces cerevisiae contain a distinct set of membrane-bound polypeptides. One of these polypeptides, termed Erv14p (ER-vesicle protein of 14 kD), corresponds to an open reading frame on yeast chromosome VII that is predicted to encode an integral membrane protein and shares sequence identity with the Drosophila cornichon gene product. Experiments with an epitope-tagged version of Erv14p indicate that this protein localizes to the ER and is selectively packaged into COPII-coated vesicles. Haploid cells that lack Erv14p are viable but display a modest defect in bud site selection because a transmembrane secretory protein, Axl2p, is not …

Developmental Regulation Of A Cyclin-Dependent Kinase Inhibitor Controls Postembryonic Cell Cycle Progression In Caenorhabditis Elegans, Yang Hong, Richard Roy, Victor Ambros

Dartmouth Scholarship

C. elegans cki-1 encodes a member of the CIP/KIP family of cyclin-dependent kinase inhibitors, and functions to link postembryonic developmental programs to cell cycle progression. The expression pattern of cki-1::GFP suggests that cki-1 is developmentally regulated in blast cells coincident with G1, and in differentiating cells. Ectopic expression of CKI-1 can prematurely arrest cells in G1, while reducing cki-1 activity by RNA-mediated interference (RNAi) causes extra larval cell divisions, suggesting a role for cki-1 in the developmental control of

INTRODUCTION

The proper development of a multicellular organism requires the precise orchestration of cell proliferation and differentiation. Despite considerable progress toward …

Molecular Basis For Effects Of Carcinogenic Heavy Metals On Inducible Gene Expression, Joshua W. Hamilton, Ronald C. Kaltreider, Olga V. Bajenova, Michael A. Ihnat, Jennifer Mccaffrey, Bruce W. Turpie, Erin E. Rowell, Jannet Oh, Michael J. Nemeth, Carrie A. Pesce, Jean P. Lariviere

Dartmouth Scholarship

Certain forms of the heavy metals arsenic and chromium are considered human carcinogens, although they are believed to act through very different mechanisms. Chromium(VI) is believed to act as a classic and mutagenic agent, and DNA/chromatin appears to be the principal target for its effects. In contrast, arsenic(III) is considered nongenotoxic, but is able to target specific cellular proteins, principally through sulfhydryl interactions. We had previously shown that various genotoxic chemical carcinogens, including chromium (VI), preferentially altered expression of several inducible genes but had little or no effect on constitutive gene expression. We were therefore interested in whether these carcinogenic …

Sec35p, A Novel Peripheral Membrane Protein, Is Required For Er To Golgi Vesicle Docking, Susan M. Vanrheenen, Xiaochun Cao, Vladimir V. Lupashin, Charles Barlowe, M. Gerard Waters

Dartmouth Scholarship

SEC35 was identified in a novel screen for temperature-sensitive mutants in the secretory pathway of the yeast Saccharomyces cerevisiae (Wuestehube et al., 1996. Genetics. 142:393–406). At the restrictive temperature, the sec35-1 strain exhibits a transport block between the ER and the Golgi apparatus and accumulates numerous vesicles. SEC35 encodes a novel cytosolic protein of 32 kD, peripherally associated with membranes. The temperature-sensitive phenotype of sec35-1 is efficiently suppressed by YPT1, which encodes the rab-like GTPase required early in the secretory pathway, or by SLY1-20, which encodes a dominant form of the ER to Golgi target …

Identification Of A Family Of Zinc Transporter Genes From Arabidopsis That Respond To Zinc Deficiency, Natasha Grotz, Tama Fox, Erin Connolly, Walter Park, Mary Lou Guerinot, David Eide

Dartmouth Scholarship

Millions of people worldwide suffer from nutritional imbalances of essential metals like zinc. These same metals, along with pollutants like cadmium and lead, contaminate soils at many sites around the world. In addition to posing a threat to human health, these metals can poison plants, livestock, and wildlife. Deciphering how metals are absorbed, transported, and incorporated as protein cofactors may help solve both of these problems. For example, edible plants could be engineered to serve as better dietary sources of metal nutrients, and other plant species could be tailored to remove metal ions from contaminated soils. We report here the …

The Carg Boxes In The Promoter Of The Arabidopsis Floral Organ Identity Gene Apetala3 Mediate Diverse Regulatory Effects, Joline J. Tilly, David W. Allen, Thomas Jack

Dartmouth Scholarship

APETALA3 is a MADS box gene required for normal development of the petals and stamens in the Arabidopsis flower. Studies in yeast, mammals and plants demonstrate that MADS domain transcription factors bind with high affinity to a consensus sequence called the CArG box. The APETALA3 promoter contains three close matches to the consensus CArG box sequence. To gain insights into the APETALA3 regulatory circuitry, we have analyzed the APETALA3 promoter using AP3::uidA(GUS) fusions. 496 base pairs of APETALA3 promoter sequence 5′ to the transcriptional start directs GUS activity in the same temporal and spatial expression pattern as the APETALA3 RNA …

The Consequences Of Changing The Top Predator In A Food Web: A Comparative Experimental Approach, Mark A. Mcpeek

Dartmouth Scholarship

Changing the top predator in a food web often results in dramatic changes in species composition at lower trophic levels; many species are extirpated and replaced by new species in the presence of the new top predator. These shifts in species composition also often result in substantial alterations in the strengths of species interactions. However, some species appear to be little affected by these changes that cause species turnover at other positions in the food web. An example of such a difference in species responses is apparent in the distributions of coenagrionid damselflies (Odonata: Zygoptera) among permanent water bodies with …

Unifying Biology: The Evolutionary Synthesis And Evolutionary Biology, Michael Dietrich

Dartmouth Scholarship

A review of a book by Vassiliki Betty Smocovitis titled Unifying Biology: The Evolutionary Synthesis\r\nand Evolutionary Biology (Princeton: Princeton University Press, 1996).

Gregor Mendel: The First Geneticist, Michael Dietrich

Dartmouth Scholarship

A review of Gregor Mendel: The First Geneticist by Vitezslav Orel. Oxford University Press, 1998.

Thermodynamic Constraints On Nitrogen Transformations And Other Biogeochemical Processes At Soil-Stream Interfaces, Lars O. Hedin, Joseph C. Von Fischer, Nathaniel E. Ostrom, Brian P. Kennedy, Michael G. Brown, G. Philip Robertson

Dartmouth Scholarship

There is much interest in biogeochemical processes that occur at the interface between soils and streams since, at the scale of landscapes, these habitats may function as control points for fluxes of nitrogen (N) and other nutrients from terrestrial to aquatic ecosystems. Here we examine whether a thermodynamic perspective can enhance our mechanistic and predictive understanding of the biogeochemical function of soil-stream interfaces, by considering how microbial communities interact with variations in supplies of electron donors and acceptors. Over a two-year period we analyzed >1400 individual samples of subsurface waters from networks of sample wells in riparian wetlands along Smith …