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[
Worm,
2014]
Mutually exclusive selection of one exon in a cluster of exons is a rare form of alternative pre-mRNA splicing, yet suggests strict regulation. However, the repertoires of regulation mechanisms for the mutually exclusive (ME) splicing in vivo are still unknown. Here, we experimentally explore putative ME exons in C. elegans to demonstrate that 29 ME exon clusters in 27 genes are actually selected in a mutually exclusive manner. Twenty-two of the clusters consist of homologous ME exons. Five clusters have too short intervening introns to be excised between the ME exons. Fidelity of ME splicing relies at least in part on nonsense-mediated mRNA decay for 14 clusters. These results thus characterize all the repertoires of ME splicing in this organism.
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[
International C. elegans Meeting,
1991]
A microbial exometabolite (ME) has been isolated which inhibits egg- laying in Caenorhabditis elegans. Nematodes exposed to active concentrations of the factor, and maintained at 22C in axenic culture ( liver extract medium), mature and grow normally. Eggs are fertilized and larvae develop and move within eggs as in untreated nematodes. However, eggs are not laid, though occasionally hatch occurs within the gonad. In shake culture of the microbe, active yellow-pigmented ME appears at 3-4 days. A concentration of 8 parts ME: 1 part liver extract completely inhibits egg-laying. Concentrations of 4 ME: 1 liver extract and 2 ME: 1 liver extract, inhibit egg-laying about 50 and 25%, respectively. Sections from nematodes exposed to extracts of a microbe showing similar properties examined by transmission electron microscopy indicated that the constrictor and dilator muscles associated with vulval function in egg-laying appear normal. ME is thermostable (at 100C for 5 min.), and the active fraction does not pass through 6,000-8,000 MW dialysis tubing. About one-half of the activity is lost when ME is dialyzed through 12,000 14,000 MW membrane tubing, suggesting the presence of at least two active fractions. Trypsinization obliterated activity. Thus far, the double control experiment with trypsin inhibitor has not yielded definitive results. SDS gel electrophoresis of boiled ME, with molecules below 8,000 MW removed by dialysis, revealed several strong protein bands, one or more of which may be ME. ME purification and characterization studies continue.
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[
Biosci Rep,
2003]
Thank you so very much for inviting me to be here. It gives me a mingled sense of humility at how much I owe to others, and of joy that the collective work on the worm has been recognized in this way.
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[
Chembiochem,
2003]
Thank you so very much for inviting me to be here. It gives me a mingled sense of humility at how much I owe to others, and of joy that the collective work on the worm has been recognised in this way.
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[
Int J Dev Biol,
2000]
1969 was a landmark year. But for me it was not Neil Armstrong's giant leap or Woodstock heralding the beginning of the end of the sixties that sticks in my mind. It was a visit I made to Cambridge to meet a "bloke who is starting a new project to study some sort of worm", as my head of department at the Medical Research Council's National Institute of Medical Research informed me...
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[
Dev Biol,
2002]
In mammals, one of the two somatic X chromosomes in the female is inactivated, thereby equalizing X chromosome-derived transcription in the two sexes, a process known as dosage compensation. In the germline, however, the situation is quite different. Both X chromosomes are transcriptionally active during female oogenesis, whereas the X and Y chromosomes are transcriptionally silent during male spermatogenesis. Previous studies suggest that Caenorhabditis elegans germline X chromosomes might have different transcriptional activity in the two sexes in a manner similar to that in mammals. Using antibodies specific to H3 methylated at either lysine 4 or lysine 9, we show that the pattern of site-specific H3 methylation is different between X chromosomes and autosomes as well as between germline X chromosomes from the two sexes in C. elegans. We show that the pachytene germline X chromosomes in both sexes lack Me(K4)H3 when compared with autosomes, consistent with their being transcriptionally inactive. This transcriptional inactivity of germline X chromosomes is apparently transient in hermaphrodites because both X chromosomes stain brightly for Me(K4)H3 after germ nuclei exit pachytene. The male single X chromosome, on the other hand, remains devoid of Me(K4)H3 staining throughout the germline. Instead, the male germline X chromosome exhibits a high level of Me(K9)H3 that is not detected on any other chromosomes in either sex, consistent with stable silencing of this chromosome. Using mutants defective in the sex determination pathway, we show that X-chromosomal Me(K9)H3 staining is determined by the sexual phenotype, and not karyotype, of the animal. We detect a similar high level of Me(K9)H3 in male mouse XY bodies, suggesting an evolutionarily conserved mechanism for silencing the X chromosome specifically in the male germline.
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[
Cancer Research,
1999]
It is an honor and a great pleasure to introduce Dr. Robert Horvitz to you as the 1998 recipient of the Alfred Sloan Prize of the General Motors Cancer Research Foundation. Let me begin by telling you a little bit about Bob's
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[
Cell,
1987]
C. elegans contains a microtubule binding protein that resembles both dynein and kinesin. This protein has a MgATPase activity and copurifies on both sucrose gradients and DEAE Sephadex columns with a polypeptide of Mr approximately 400 kd. The ATPase activity is 50% inhibited by 10 microM vanadate, 1 mM N-ethyl maleimide, or 5 mM AMP- PNP; it is enhanced 50% by 0.2% Triton. The 400 kd polypeptide is cleaved at a single site by ultraviolet light in the presence of ATP and vanadate. In these ways, the protein resembles dynein. The protein also promotes ATP-dependent translocation of microtubules or axonemes, "plus" ends trailing. This property is kinesin-like; however, the motility is blocked by 5 microM vanadate, 1 mM N-ethyl maleimide, 0.5 mM ATP-gamma-S, or by ATP-vanadate-UV cleavage of the 400 kd polypeptide, characteristics that differ from kinesin. We propose that this protein is a novel microtubule translocator.
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[
Worm Breeder's Gazette,
1986]
We have identified a protein in C. bines properties of the flagellar ATPase, dynein with those of the microtubule-dependent translocator, kinesin. The microtubule stabilizing drug, taxol, has been used to drive microtubule assembly in extracts of either gravid adult worms or of embryos, and the resulting polymers have been isolated by differential centrifugation. One of the microtubule-associated proteins (Mr. approx. 400K) can be extracted from the polymer by 10 mM ATP and 100 mM NaCl. This polypeptide and a Mg-ATPase activity cosediment on sucrose density gradients at approximately 20 S. The specific activity of the peak fraction is 60 - 120 nanomoles ATP hydrolyzed/milligram protein/min. ( conditions have not yet been optimized). The activity is more than 50Z inhibited by either 10 uM vanadate, 1 mM N-ethyl maleimide or by 5 mM AMP-PNP. The ATPase is enhanced 50Z by 0.2Z Triton X-100. These properties are dynein-like. When the 20 S protein is mixed with either microtubules or flagellar axonemes on slide, it promotes a nucleotide triphosphate-dependent microtubule translocation. Axonemes glide with their 'plus' ends trailing. These properties are kinesin-like. However, microtubules move at about 0.8 - 1.0 um/sec., about twice as fast as with kinesin under conditions of saturating ATP. Furthermore, the motion is ATP-specific and is blocked by either 10 uM vanadate, 1mM N-ethyl maleimide, or by 0.5 mM ATP-gamma-S. Motility is slowed but not blocked by [AMP-PNP] = [ATP]. These characteristics and the presence of an ATPase activity differ from the properties described for kinesin. The roughly parallel inhibition of the ATPase and the motility by several reagents suggests that the enzyme activity and the motility are caused by the same protein or protein complex. We therefore propose that the 400 K protein from C. rotubule translocator which possesses properties of both dynein and kinesin.
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[
International C. elegans Meeting,
1987]