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Full-Text Articles in Life Sciences

Ets-Core Binding Factor: A Common Composite Motif In Antigen Receptor Gene Enhancers, Batu Erman, Marta Cortes, Barbara S. Nikolajczyk, Nancy A. Speck, Ranjan Sen Dec 1997

Ets-Core Binding Factor: A Common Composite Motif In Antigen Receptor Gene Enhancers, Batu Erman, Marta Cortes, Barbara S. Nikolajczyk, Nancy A. Speck, Ranjan Sen

Dartmouth Scholarship

A tripartite domain of the murine immunoglobulin μ heavy-chain enhancer contains the μA and μB elements that bind ETS proteins and the μE3 element that binds leucine zipper-containing basic helix-loop-helix (bHLH-zip) factors. Analysis of the corresponding region of the human μ enhancer revealed high conservation of the μA and μB motifs but a striking absence of the μE3 element. Instead of bHLH-zip proteins, we found that the human enhancer bound core binding factor (CBF) between the μA and μB elements; CBF binding was shown to be a common feature of both murine and human enhancers. Furthermore, mutant enhancers that bound …


Coupled Er To Golgi Transport Reconstituted With Purified Cytosolic Proteins, Charles Barlowe Dec 1997

Coupled Er To Golgi Transport Reconstituted With Purified Cytosolic Proteins, Charles Barlowe

Dartmouth Scholarship

A cell-free vesicle fusion assay that reproduces a subreaction in transport of pro-alpha-factor from the ER to the Golgi complex has been used to fractionate yeast cytosol. Purified Sec18p, Uso1p, and LMA1 in the presence of ATP and GTP satisfies the requirement for cytosol in fusion of ER-derived vesicles with Golgi membranes. Although these purified factors are sufficient for vesicle docking and fusion, overall ER to Golgi transport in yeast semi-intact cells depends on COPII proteins (components of a membrane coat that drive vesicle budding from the ER). Thus, membrane fusion is coupled to vesicle formation in ER to Golgi …


Competitive Interactions Among Symbiotic Fungi Of The Southern Pine Beetle, Kier D. Klepzig, Richard T. Wilkens Nov 1997

Competitive Interactions Among Symbiotic Fungi Of The Southern Pine Beetle, Kier D. Klepzig, Richard T. Wilkens

Dartmouth Scholarship

The southern pine beetle, a damaging pest of conifers, is intimately linked to three symbiotic fungi. Two fungi, Ceratocystiopsis ranaculosus and Entomocorticium sp. A, are transported within specialized structures (mycangia) in the beetle exoskeleton and are mutualists of the beetle. A third fungus, Ophiostoma minus, is transported externally on the beetle exoskeleton (phoretically) and is an antagonist of the beetle. This study examined competitive interactions among these three fungi. The results of de Wit replacement series and primary and secondary resource capture assays with these fungi provide strong evidence for differential competition between the phoretic and mycangial fungi. O. minus …


Site-Dependent Regulation Of Population Size: A New Synthesis, Nicholas L. Rodenhouse, Thomas W. Sherry, Richard T. Holmes Oct 1997

Site-Dependent Regulation Of Population Size: A New Synthesis, Nicholas L. Rodenhouse, Thomas W. Sherry, Richard T. Holmes

Dartmouth Scholarship

The nature and extent of population regulation remains a principal unanswered question for many types of organisms, despite extensive research. In this paper, we provide a new synthesis of theoretical and empirical evidence that elucidates and extends a mechanism of population regulation for species whose individuals preemptively use sites that differ in suitability. The sites may be territories, refuges from predation, oviposition sites, etc. The mechanism, which we call site dependence, is not an alternative to density dependence; rather, site dependence is one of several mechanisms that potentially generate the negative feedback required for regulation. Site dependence has two major …


The Interaction Between Cytoplasmic Dynein And Dynactin Is Required For Fast Axonal Transport, Clare M. Waterman-Storer, Sher B. Karki, Sergei A. Kuznetsov, Joel S. Tabb, Dieter G. Weiss, George M. Langford, Erika L. F. Holzbaur Oct 1997

The Interaction Between Cytoplasmic Dynein And Dynactin Is Required For Fast Axonal Transport, Clare M. Waterman-Storer, Sher B. Karki, Sergei A. Kuznetsov, Joel S. Tabb, Dieter G. Weiss, George M. Langford, Erika L. F. Holzbaur

Dartmouth Scholarship

Fast axonal transport is characterized by the bidirectional, microtubule-based movement of membranous organelles. Cytoplasmic dynein is necessary but not sufficient for retrograde transport directed from the synapse to the cell body. Dynactin is a heteromultimeric protein complex, enriched in neurons, that binds to both microtubules and cytoplasmic dynein. To determine whether dynactin is required for retrograde axonal transport, we examined the effects of anti-dynactin antibodies on organelle transport in extruded axoplasm. Treatment of axoplasm with antibodies to the p150(Glued) subunit of dynactin resulted in a significant decrease in the velocity of microtubule-based organelle transport, with many organelles bound along microtubules. …


Cell Signaling Pathways Elicited By Asbestos, B T. Mossman, S Faux, Y Janssen, L A. Jimenez, Cynthia Timblin, Christine Zanella, Jonathan Goldberg, Eric Walsh, Aaron Barchowsky, Kevin Driscoll Sep 1997

Cell Signaling Pathways Elicited By Asbestos, B T. Mossman, S Faux, Y Janssen, L A. Jimenez, Cynthia Timblin, Christine Zanella, Jonathan Goldberg, Eric Walsh, Aaron Barchowsky, Kevin Driscoll

Dartmouth Scholarship

In recent years, it has become apparent that minerals can trigger alterations in gene expression by initiating signaling events upstream of gene transactivation. These cascades may be initiated at the cell surface after interaction of minerals with the plasma membrane either through receptorlike mechanisms or integrins. Alternatively, signaling pathways may be stimulated by active oxygen species generated both during phagocytosis of minerals and by redox reactions on the mineral surface. At least two signaling cascades linked to activation of transcription factors, i.e., DNA-binding proteins involved in modulating gene expression and DNA replication, are stimulated after exposure of lung cells to …


The Role Of Proximal And Distal Sequence Variations In The Presentation Of An Immunodominant Ctl Epitope Encoded By The Ecotropic Ak7 Mulv, Victor Kim, William R. Green Jul 1997

The Role Of Proximal And Distal Sequence Variations In The Presentation Of An Immunodominant Ctl Epitope Encoded By The Ecotropic Ak7 Mulv, Victor Kim, William R. Green

Dartmouth Scholarship

An emv-14-derived, replication-competent ecotropic murine leukemia virus [MuLV], designated AK7, was previously cloned from the AKXL-5 recombinant inbred mouse strain and partially characterized. While genetically encoding for an envelope-derived immunodominant CTL epitope [KSPWFTTL] located in the transmembrane region of p15TM, this virus, unlike the emv-11-derived virus AKR623, fails to be efficiently recognized by AKR/Gross MuLV-specific cytotoxic T lymphocytes [CTL]. AK7 thus provides the opportunity to study the role of retroviral sequence variations that are located outside of the immunodominant epitope as a mechanism of escape from CTL-mediated immune surveillance. In an attempt to identify which region[s] of the AK7 genome …


Head Direction Cells And Episodic Spatial Information In Rats Without A Hippocampus, Edward J. Golob, Jeffrey S. Taube Jul 1997

Head Direction Cells And Episodic Spatial Information In Rats Without A Hippocampus, Edward J. Golob, Jeffrey S. Taube

Dartmouth Scholarship

To successfully navigate through the environment animals rely on information concerning their directional heading and location. Many cells within the postsubiculum and anterior thalamus discharge as a function of the animal’s head direction (HD), while many cells in the hippocampus discharge in relation to the animal’s location. We placed lesions in the hippocampus and recorded from HD cells in the postsubiculum and anterior thalamus. Lesions of the hippocampus did not disrupt the HD cell signal in either brain area, indicating that the HD cell signal must be generated by structures external to the hippocampus. In addition, each cell’s preferred firing …


Phosphorylation Regulates The Assembly Of Numa In A Mammalian Mitotic Extract, Alejandro Saredi, Louisa Howard, Duane A. Compton Jun 1997

Phosphorylation Regulates The Assembly Of Numa In A Mammalian Mitotic Extract, Alejandro Saredi, Louisa Howard, Duane A. Compton

Dartmouth Scholarship

NuMA is a 236 kDa nuclear protein that is required for the organization of the mitotic spindle. To determine how NuMA redistributes in the cell during mitosis, we have examined the behavior of NuMA in a mammalian mitotic extract under conditions conducive to the reassembly of interphase nuclei. NuMA is a soluble protein in mitotic extracts prepared from synchronized cultured cells, but forms insoluble structures when the extract becomes non-mitotic (as judged by the inactivation of cdc2/cyclin B kinase and the disappearance of mpm-2-reactive antigens). These NuMA-containing structures are irregularly shaped particles of 1–2 microm in diameter and their assembly …


Identification Of A Novel Antiapoptotic Functional Domain In Simian Virus 40 Large T Antigen., Suzanne D. Conzen, Christine A. Snay, Charles N. Cole Jun 1997

Identification Of A Novel Antiapoptotic Functional Domain In Simian Virus 40 Large T Antigen., Suzanne D. Conzen, Christine A. Snay, Charles N. Cole

Dartmouth Scholarship

The ability of DNA tumor virus proteins to trigger apoptosis in mammalian cells is well established. For example, transgenic expression of a simian virus 40 (SV40) T-antigen N-terminal fragment (N-termTag) is known to induce apoptosis in choroid plexus epithelial cells. SV40 T-antigen-induced apoptosis has generally been considered to be a p53-dependent event because cell death in the brain is greatly diminished in a p53-/- background strain and is abrogated by expression of wild-type (p53-binding) SV40 T antigen. We now show that while N-termTags triggered apoptosis in rat embryo fibroblasts cultured in low serum, expression of full-length T antigens unable to …


Both An N-Terminal 65-Kda Domain And A C-Terminal 30-Kda Domain Of Seca Cycle Into The Membrane At Secyeg During Translocation, Jerry Eichler, William Wickner Apr 1997

Both An N-Terminal 65-Kda Domain And A C-Terminal 30-Kda Domain Of Seca Cycle Into The Membrane At Secyeg During Translocation, Jerry Eichler, William Wickner

Dartmouth Scholarship

SecA, a 102-kDa hydrophilic protein, couples the energy of ATP binding to the translocation of preprotein across the bacterial inner membrane. SecA function and topology were studied with metabolically labeled [35S]SecA and with inner membrane vesicles from cells that overex- pressed SecYEGDFyajC, the integral domain of preprotein translocase. During translocation in the presence of ATP and preprotein, a 65-kDa N-terminal domain of SecA is protected from proteolytic digestion through insertion into the mem- brane, as previously reported for a 30-kDa C-terminal domain [Economou, A. & Wickner, W. (1994) Cell 78, 835–843]. Insertion of both domains occurs at saturable SecYEGDFyajC sites …


I2b Is A Small Cytosolic Protein That Participates In Vacuole Fusion, Paul Slusarewicz, Zuoyu Xu, Kimberly Seefeld, Albert Haas, William T. Wickner Mar 1997

I2b Is A Small Cytosolic Protein That Participates In Vacuole Fusion, Paul Slusarewicz, Zuoyu Xu, Kimberly Seefeld, Albert Haas, William T. Wickner

Dartmouth Scholarship

Saccharomyces cerevisiae vacuole inheritance requires two low molecular weight activities, LMA1 and LMA2. LMA1 is a heterodimer of thioredoxin and protease B inhibitor 2 (IB2). Here we show that the second low molecular weight activity (LMA2) is monomeric IB2. Though LMA2 / IB2 was initially identified as a protease B inhibitor, this protease inhibitor activity is not related to its ability to promote vacuole fusion: ( i ) Low M r protease B inhibitors cannot substitute for LMA1 or LMA2, ( ii ) LMA1 and LMA2 promote the fusionof vacuoles from a strain that …


Docking Of Yeast Vacuoles Is Catalyzed By The Ras-Like Gtpase Ypt7p After Symmetric Priming By Sec18p (Nsf), Andreas Mayer, William Wickner Jan 1997

Docking Of Yeast Vacuoles Is Catalyzed By The Ras-Like Gtpase Ypt7p After Symmetric Priming By Sec18p (Nsf), Andreas Mayer, William Wickner

Dartmouth Scholarship

Vacuole inheritance in yeast involves the for- mation of tubular and vesicular “segregation struc- tures” which migrate into the bud and fuse there to es- tablish the daughter cell vacuole. Vacuole fusion has been reconstituted in vitro and may be used as a model for an NSF-dependent reaction of priming, docking, and fusion. We have developed biochemical and micro- scopic assays for the docking step of in vitro vacuole fusion and characterized its requirements. The vacu- oles must be primed for docking by the action of Sec17p ( a -SNAP) and Sec18p (NSF). Priming is neces- sary for both fusion …


A Heterodimer Of Thioredoxin And Ib2 Cooperates With Sec18p (Nsf) To Promote Yeast Vacuole Inheritance, Zuoyu Xu, Andreas Mayer, Eric Muller, William Wickner Jan 1997

A Heterodimer Of Thioredoxin And Ib2 Cooperates With Sec18p (Nsf) To Promote Yeast Vacuole Inheritance, Zuoyu Xu, Andreas Mayer, Eric Muller, William Wickner

Dartmouth Scholarship

Early in S phase, the vacuole (lysosome) of Saccharomyces cerevisiae projects a stream of vesicles and membranous tubules into the bud where they fuse and establish the daughter vacuole. This inheritance reaction can be studied in vitro with isolated vacuoles. Rapid and efficient homotypic fusion between saltwashed vacuoles requires the addition of only two purified soluble proteins, Sec18p (NSF) and LMA1, a novel heterodimer with a thioredoxin subunit. We now report the identity of the second subunit of LMA1 as IB2, a previously identified cytosolic inhibitor of vacuolar proteinase B. Both subunits are needed for efficient vacuole inheritance in vivo …


Cyclic Amp And Its Receptor Protein Negatively Regulate The Coordinate Expression Of Cholera Toxin And Toxin-Coregulated Pilus In Vibrio Cholerae, Karen Skorupski, Ronald K. Taylor Jan 1997

Cyclic Amp And Its Receptor Protein Negatively Regulate The Coordinate Expression Of Cholera Toxin And Toxin-Coregulated Pilus In Vibrio Cholerae, Karen Skorupski, Ronald K. Taylor

Dartmouth Scholarship

Insertion mutations in two Vibrio cholerae genes, cya and crp, which encode adenylate cyclase and the cyclic AMP (cAMP) receptor protein (CRP), respectively, derepressed the expression of a chromosomal cholera toxin (CT) promoter-lacZ fusion at the nonpermissive temperature of 37 degrees C. In the classical biotype strain O395, the crp mutation increased the production of both CT and toxin-coregulated pilus (TCP) in vitro under a variety of growth conditions not normally permissive for their expression. The most dramatic increase in CT and TCP was observed with the crp mutant in Luria-Bertani (LB) medium pH 8.5, at 30 degrees C. El …