-
[
Genome Biol,
2000]
SUMMARY: The F-box is a protein motif of approximately 50 amino acids that functions as a site of protein-protein interaction. F-box proteins were first characterized as components of SCF ubiquitin-ligase complexes (named after their main components, Skp I, Cullin, and an F-box protein), in which they bind substrates for ubiquitin-mediated proteolysis. The F-box motif links the F-box protein to other components of the SCF complex by binding the core SCF component Skp I. F-box proteins have more recently been discovered to function in non-SCF protein complexes in a variety of cellular functions. There are 11 F-box proteins in budding yeast, 326 predicted in Caenorhabditis elegans, 22 in Drosophila, and at least 38 in humans. F-box proteins often include additional carboxy-terminal motifs capable of protein-protein interaction; the most common secondary motifs in yeast and human F-box proteins are WD repeats and leucine-rich repeats, both of which have been found to bind phosphorylated substrates to the SCF complex. The majority of F-box proteins have other associated motifs, and the functions of most of these proteins have not yet been defined.
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[
Worm Breeder's Gazette,
1995]
lin-49, an essential gene required for normal F and U cells
-
[
Parasitol Today,
1988]
Ivermectin is a semi-synthetic macrocyclic lactone (Fig. I) active in single low doses against many parasites - particularly nematodes and arthropods. It has been registered for animal health use since early 1985, and was earlier this year approved for human use by the French Directorate o f Pharmacy and Drugs. Of particular interest is ivermectin's potential as a micro filaricide for treatment o f onchocerciasis. Clinical trials leave little doubt about the potential o f ivermectin as a therapeutic tool for symptomatic relief from the effects o f infection with Onchocerca volvulus, and the drug is also recognized to have potential in reducing transmission o f the parasite. The manufacturers (Merck, Sharp and Dohme) recently arranged to provide the drug free o f charge to the WHO for mass trials against onchocerciasis in 12 African and Central American countries. In this article we focus on the pharmacological properties o f ivermectin, with a brief consideration of its absorption, fate, excretion and side-effects, and a discussion o f its micro filaricidal action.
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[
East Coast Worm Meeting,
2000]
Recent reports (see below) showed that high pressure freezing (HPF) followed by freeze substitution is superior to chemical immersion fixation for C. elegans. HPF captures a more "life-like" view of the worm's ultrastructure. We compared HPF and a related technique, rapid freezing onto a metal mirror (MMF). For MMF, live animals on a small piece of filter paper are plunged against a metal mirror in liquid nitrogen. Freezing damage is often a problem, but some animals seem to be well frozen throughout. For HPF, we have tried two methods to concentrate live animals into a small metal planchette (see Lavin and McDonald ref's below). Further processing is the same for both methods. While holding at very low temperatures, the samples are freeze substituted into 1% osmium tetroxide in acetone, then embedded into plastic resin and cured for thin sectioning. By TEM fast-frozen worms reveal excellent views of membrane events and organelles. For instance, we see active endocytosis events that are not captured by chemical fixation. The microtubule network is better preserved and the basal laminae look strikingly different. Sample images are shown at www.aecom.yu.edu/wormem/new.html. HPF and MMF also hold promise for high resolution immunoEM. By reducing the osmium content and adding a dilute aldehyde fixative to the freeze substitution medium, we can better preserve structure than by our microwave technique (Paupard et al., submitted). We have successfully localized epitopes in thin sections from HPF samples. We are conducting HPF trials with Stan Erlandson and Ya Chen at the U. of Minnesota. MMF equipment is available here at Einstein and elsewhere. HPF machines are available to outside users in Madison, Berkeley, Minneapolis, and Albany. As our skills improve, we will offer such services to the C. elegans community. For further information on HPF, we recommend the following sources: Colleen Lavin's website at www.geology.wisc.edu/~uwmr/coating.html Martin Muller's website at www.em.biol.ethz.ch/ Kent McDonald, Methods in Molecular Biology, vol 117, pp. 77-97 (Humana Press) 1999.
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[
West Coast Worm Meeting,
2000]
Several recent reports (see below) have demonstrated that C. elegans tissues can be very well preserved for electron microscopy by high pressure freezing (HPF) followed by freeze substitution, perhaps substantially better than by standard chemical immersion fixation. HPF shows the potential to capture a more "life-like" view of the worm's ultrastructure. We have been testing both HPF and a related technique, rapid freezing on a metal mirror (MMF) followed by freeze substitution. Both methods obtain similar high quality fixation, although there are some freezing artifacts using the metal mirror device that are eliminated in HPF. For MMF, live animals are concentrated on a small piece of filter paper and plunged against a metal mirror at liquid nitrogen temperature. While freezing damage often occurs about 5-15 microns into the worms, some animals are very well frozen throughout. The frozen samples are held at low temperature and freeze substituted into 1% osmium tetroxide in acetone, then embedded into plastic resin and cured for thin sectioning. For HPF, we have tried two methods to concentrate live animals into small metal planchette, either holding the animals within fine strands of dialysis tubing (C. Lavin, pers. comm.), or mixing them into a slurry of yeast paste to form a space-filling solid support (McDonald, 1999). Examination of fast-frozen specimens by TEM reveals excellent views of membrane events and organelles. For instance, we see many omega figures on coelomocytes which are indicative of active endocytosis, events which are not commonly captured by chemical fixation. Synaptic active zones and vesicles are well preserved, as are their relationships to microtubules. A network of microtubules can also been seen extending to the periphery of hypodermis. Basal laminae look strikingly different, much looser and more mesh-like when compared to chemical fixation. Sample images are shown on our website [www.aecom.yu.edu/wormem/new.html]. These two preparation methods, HPF and MMF, also hold great promise for high resolution immuno-EM. By reducing the osmium content and adding a dilute aldheyde fixation to the freeze substitution medium, we can obtain better resolution than is currently possible by our microwave technique. We have successfully localized epitopes in thin sections from HPF samples. MMF equipment is available here at Einstein campus. We are conducting HPF trials with the help of Stan Erlandson and Ya Chen at the University of Minnesota. As our skills improve, we will be happy to offer such services to the C. elegans community. For further information on HPF, we recommend the following sources: Colleen Lavin's website at www.geology.wisc.edu/~uwmr/caoting.html Martin Muller's website at www.em.bio.ethz.ch/ Kent McDonald, Methods in Molecular Biology, vol 117, pp. 77-97 (Human Press) 1999. In the U.S., there are HPF machines open to the outside users in Madison, Berkeley, Minneapolis and Albany.
-
[
Midwest Worm Meeting,
2000]
Recent reports (see below) showed that high pressure freezing (HPF) followed by freeze substitution is superior to chemical immersion fixation for C. elegans. HPF captures a more "life-like" view of the worm's ultrastructure. We compared HPF and a related technique, rapid freezing onto a metal mirror (MMF). For MMF, live animals on a small piece of filter paper are plunged against a metal mirror in liquid nitrogen. Freezing damage is often a problem, but some animals seem to be well frozen throughout. For HPF, we have tried two methods to concentrate live animals into a small metal planchette (see Lavin and McDonald ref's below). Further processing is the same for both methods. While holding at very low temperatures, the samples are freeze substituted into 1% osmium tetroxide in acetone, then embedded into plastic resin and cured for thin sectioning. By TEM fast-frozen worms reveal excellent views of membrane events and organelles. For instance, we see active endocytosis events that are not captured by chemical fixation. The microtubule network is better preserved and the basal laminae look strikingly different. Sample images are shown at www.aecom.yu.edu/wormem/new.html. HPF and MMF also hold promise for high resolution immunoEM. By reducing the osmium content and adding a dilute aldehyde fixative to the freeze substitution medium, we can better preserve structure than by our microwave technique (Paupard et al., submitted). We have successfully localized epitopes in thin sections from HPF samples. We are conducting HPF trials with Stan Erlandson and Ya Chen at the U. of Minnesota. MMF equipment is available here at Einstein and elsewhere. HPF machines are available to outside users in Madison, Berkeley, Minneapolis, and Albany. As our skills improve, we will offer such services to the C. elegans community. For further information on HPF, we recommend the following sources: Colleen Lavin's website at www.geology.wisc.edu/~uwmr/coating.html Martin Muller's website at www.em.biol.ethz.ch/ Kent McDonald, Methods in Molecular Biology, vol 117, pp. 77-97 (Humana Press) 1999.
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[
Curr Biol,
2015]
Establishment of a neuronal system requires proper regulation of the F-actin-rich leading edges of migrating neurons and neurite growth cones. A new study shows that RhoG signals through the multi-domain protein anillin to stabilize F-actin in these structures.
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[
Proc Natl Acad Sci U S A,
2010]
The ternary complex of cadherin, beta-catenin, and alpha-catenin regulates actin-dependent cell-cell adhesion. alpha-Catenin can bind beta-catenin and F-actin, but in mammals alpha-catenin either binds beta-catenin as a monomer or F-actin as a homodimer. It is not known if this conformational regulation of alpha-catenin is evolutionarily conserved. The Caenorhabditis elegans alpha-catenin homolog HMP-1 is essential for actin-dependent epidermal enclosure and embryo elongation. Here we show that HMP-1 is a monomer with a functional C-terminal F-actin binding domain. However, neither full-length HMP-1 nor a ternary complex of HMP-1-HMP-2(beta-catenin)-HMR-1(cadherin) bind F-actin in vitro, suggesting that HMP-1 is auto-inhibited. Truncation of either the F-actin or HMP-2 binding domain of HMP-1 disrupts C. elegans development, indicating that HMP-1 must be able to bind F-actin and HMP-2 to function in vivo. Our study defines evolutionarily conserved properties of alpha-catenin and suggests that multiple mechanisms regulate alpha-catenin binding to F-actin.
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[
BMC Genomics,
2021]
Background: F-box proteins represent a diverse class of adaptor proteins of the ubiquitin-proteasome system (UPS) that play critical roles in the cell cycle, signal transduction, and immune response by removing or modifying cellular regulators. Among closely related organisms of the Caenorhabditis genus, remarkable divergence in F-box gene copy numbers was caused by sizeable species-specific expansion and contraction. Although F-box gene number expansion plays a vital role in shaping genomic diversity, little is known about molecular evolutionary mechanisms responsible for substantial differences in gene number of F-box genes and their functional diversification in Caenorhabditis. Here, we performed a comprehensive evolution and underlying mechanism analysis of F-box genes in five species of Caenorhabditis genus, including C. brenneri, C. briggsae, C. elegans, C. japonica, and C. remanei.Results: Herein, we identified and characterized 594, 192, 377, 39, 1426 F-box homologs encoding putative F-box proteins in the genome of C. brenneri, C. briggsae, C. elegans, C. japonica, and C. remanei, respectively. Our work suggested that extensive species-specific tandem duplication followed by a small amount of gene loss was the primary mechanism responsible for F-box gene number divergence in Caenorhabditis genus. After F-box gene duplication events occurred, multiple mechanisms have contributed to gene structure divergence, including exon/intron gain/loss, exonization/pseudoexonization, exon/intron boundaries alteration, exon splits, and intron elongation by tandem repeats. Based on high-throughput RNA sequencing data analysis, we proposed that F-box gene functions have diversified by sub-functionalization through highly divergent stage-specific expression patterns in Caenorhabditis species.Conclusions: Massive species-specific tandem duplications and occasional gene loss drove the rapid evolution of the F-box gene family in Caenorhabditis, leading to complex gene structural variation and diversified functions affecting growth and development within and among Caenorhabditis species. In summary, our findings outline the evolution of F-box genes in the Caenorhabditis genome and lay the foundation for future functional studies.
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[
West Coast Worm Meeting,
2004]
In C. elegans epidermal intermediate filaments (IFs) and their associated structures, the trans-epidermal attachments, are essential for embryonic epidermal elongation (Woo et al 2004). The formation of muscle contractile units and trans-epidermal attachments are mutually dependent during epidermal elongation. To understand how the connection between epidermis and muscle is established and how the two tissues communicate during organogenesis, we performed a screen for epidermal elongation-defective mutants. One locus identified in this screen was defined by three lethal alleles and mapped to the cluster of LG II. Subsequent analysis showed that these mutations were allelic to
vab-13 and
ven-3 . By genetic mapping and allele sequencing we showed that all these mutations affect F10E7.4, which encodes the C. elegans member of the F-spondin family of secreted proteins. F-spondin has been shown to play roles in axon guidance, cell migration, and angiogenesis. Our genetic analysis shows that in C. elegans F-spondin is required for epidermal elongation and muscle attachment, as well as for proper positioning of neuronal processes. Using GFP reporters, we found that F-spondin is expressed in body muscle cells and is a secreted protein. Thus, F-spondin may function in embryogenesis in communication between muscle and epidermis. Immunostaining of F-spondin mutants suggest that F-spondin may indirectly affect the organization of epidermal actin microfilaments and trans-epidermal attachments . We are examining the expression patterns of muscle and basement membrane components in F-spondin mutants. To study the signaling pathways regulated by F-spondin, we are testing mutations in candidate receptor genes for genetic interactions with F-spondin mutations.