Showing papers by "Junho Lee published in 2000"
TL;DR: A screen for synthetic enhancers of sli-1 identified ark-1 (forAck-related tyrosine kinase), a novel inhibitor of let-23 EGFR signaling in C. elegans, which suggests that ARK-1 acts upstream of RAS and is dependent upon SEM-5.
99 citations
TL;DR: It is demonstrated that diverse types of GARs are present in C. elegans and that GAR‐2 showed virtually no response to muscarinic antagonists such as atropine, scopolamine, and pirenzepine.
Abstract: We have previously identified two G protein-linked acetylcholine receptors (GARs), GAR-1 and GAR-3, in the nematode Caenorhabditis elegans. Whereas GAR-3 is a homologue of muscarinic acetylcholine receptors (mAChRs), GAR-1 is similar to but pharmacologically distinct from mAChRs. In the current work we isolated a new type of GAR using C. elegans genome sequence information. This receptor, named GAR-2, consists of 614 amino acid residues and has seven putative transmembrane domains. Database searches indicate that GAR-2 is most similar to GAR-1 and closely related to GAR-3/mAChRs. The overall amino acid sequence identities to GAR-1 and GAR-3 are approximately 32 and approximately 23%, respectively. When GAR-2 was coexpressed with the G protein-activated inwardly rectifying K(+) (GIRK1) channel in Xenopus oocytes, acetylcholine was able to evoke the GIRK current in a dose-dependent fashion. Oxotremorine, a classical muscarinic agonist, had little effect on the receptor, indicating that GAR-2 is pharmacologically different from mAChRs but rather similar to GAR-1. GAR-2 differs from GAR-1, however, in that it showed virtually no response to muscarinic antagonists such as atropine, scopolamine, and pirenzepine. Expression studies using green fluorescent protein reporter gene fusion revealed that GAR-2 is expressed in a subset of C. elegans neurons, distinct from those expressing GAR-1. Together with our previous reports, this study demonstrates that diverse types of GARs are present in C. elegans.
76 citations
TL;DR: APm-1 and unc-101 encode two highly related micro1 chains that share redundant and distinct functions within AP-1 clathrin-associated protein complexes of the same tissue.
Abstract: In the nematode Caenorhabditis elegans, there exist two μ1 medium chains of the AP-1 clathrin-associated protein complex. Mutations of unc-101, the gene that encodes one of the μ1 chains, cause pleiotropic effects (Lee et al., 1994 blue right-pointing triangle). In this report, we identified and analyzed the second μ1 chain gene, apm-1. Unlike the mammalian homologs, the two medium chains are expressed ubiquitously throughout development. RNA interference (RNAi) experiments with apm-1 showed that apm-1 and unc-101 were redundant in embryogenesis and in vulval development. Consistent with this, a hybrid protein containing APM-1, when overexpressed, rescued the phenotype of an unc-101 mutant. However, single disruptions of apm-1 or unc-101 have distinct phenotypes, indicating that the two medium chains may have distinct functions. RNAi of any one of the small or large chains of AP-1 complex (σ1, β1, or γ) showed a phenotype identical to that caused by the simultaneous disruption of unc-101 and apm-1, but not that by single disruption of either gene. This suggests that the two medium chains may share large and small chains in the AP-1 complexes. Thus, apm-1 and unc-101 encode two highly related μ1 chains that share redundant and distinct functions within AP-1 clathrin-associated protein complexes of the same tissue.
70 citations
TL;DR: The overexpressed polypeptide showed an optimal activity for removing negative DNA supercoils at a relatively high temperature of 52-57 degrees C, which is similar to the optimum temperatures of other eukaryotic DNA topoisomerase III enzymes.
Abstract: To investigate the function of a DNA topoisomerase III enzyme in Caenorhabditis elegans, the full-length cDNA of C.elegans DNA topoisomerase IIIα was cloned. The deduced amino acid sequence exhibited identities of 48 and 39% with those of human DNA topoisomerase IIIα and Saccharomyces cerevisiae DNA topoisomerase III, respectively. The overexpressed polypeptide showed an optimal activity for removing negative DNA supercoils at a relatively high temperature of 52–57°C, which is similar to the optimum temperatures of other eukaryotic DNA topoisomerase III enzymes. When topoisomerase IIIα expression was interfered with by a cognate double-stranded RNA injection, pleiotropic phenotypes with abnormalities in germ cell proliferation, oogenesis and embryogenesis appeared. These phenotypes were well correlated with mRNA expression localized in the meiotic cells of gonad and early embryonic cells.
19 citations
TL;DR: A cDNA encoding the Caenorhabditis elegans homolog of mammalian PEBP2alpha is isolated and it is found that a 301-aa protein with a highly conserved Runt domain is present at the C-terminal end.
17 citations