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41.
Wingert RA Galloway JL Barut B Foott H Fraenkel P Axe JL Weber GJ Dooley K Davidson AJ Schmid B Schmidt B Paw BH Shaw GC Kingsley P Palis J Schubert H Chen O Kaplan J Zon LI;Tübingen Screen Consortium 《Nature》2005,436(7053):1035-1039
Iron is required to produce haem and iron-sulphur (Fe-S) clusters, processes thought to occur independently. Here we show that the hypochromic anaemia in shiraz (sir) zebrafish mutants is caused by deficiency of glutaredoxin 5 (grx5), a gene required in yeast for Fe-S cluster assembly. We found that grx5 was expressed in erythroid cells of zebrafish and mice. Zebrafish grx5 rescued the assembly of grx5 yeast Fe-S, showing that the biochemical function of grx5 is evolutionarily conserved. In contrast to yeast, vertebrates use iron regulatory protein 1 (IRP1) to sense intracellular iron and regulate mRNA stability or the translation of iron metabolism genes. We found that loss of Fe-S cluster assembly in sir animals activated IRP1 and blocked haem biosynthesis catalysed by aminolaevulinate synthase 2 (ALAS2). Overexpression of ALAS2 RNA without the 5' iron response element that binds IRP1 rescued sir embryos, whereas overexpression of ALAS2 including the iron response element did not. Further, antisense knockdown of IRP1 restored sir embryo haemoglobin synthesis. These findings uncover a connection between haem biosynthesis and Fe-S clusters, indicating that haemoglobin production in the differentiating red cell is regulated through Fe-S cluster assembly. 相似文献
42.
B. E. Leonard F. Ramaekers H. Rigter 《Cellular and molecular life sciences : CMLS》1976,32(7):901-902
Summary Monoamine levels in brain and urine of homozygous and heterozygous diabetes insipidus (DI) rats (Brattleboro strain) were assessed. Homozygous DI rats had a higher whole brain content of serotonin than their heterozygous littermates. However, when corrected for differences in brain weight, homozygous DI also appeared to have higher brain concentrations of noradrenaline, tyrosine and GABA. The total 24 h excretion of all amines and their precursors was greater in the homozygous than in the heterozygous rats.The authors thankHerman Müller andIneke van de Veerdonk for their assistance with part of this study. 相似文献
43.
Wildland shrubs have gained considerable attention in recent years due to increasing recognition of their values as animal feed, as wildlife habitat, and for land reclamation. Better management of the shrub resource will be possible through clearer taxonomic identification and better understanding of phylogenetic relationships. This study applied polyacrylamide gel electrophoresis and further developed this technique to address genetic relationships among 16 paired shrub species (genera: Artemisia, Chrysothamnus, Atriplex, Ceratoides, Sarcobatus, Purshia, Cowania, and Cercocarpus [Compositae, Chenopodiaceae, Rosaceae]). Cluster analysis of similarity values for total protein and 14 isoenzyme systems gave patterns of species relationships expected from classical morphological grounds with two minor exceptions. Isoenzyme analyses showed promise for solving taxonomic, phylogenetic, and population genetics problems. 相似文献
44.
Western records for 27 species of Trichoptera are given; a majority of the records are from the Beartooth Mountains of northwestern Wyoming. In addition, examples of variation in the male genitilia of Limnephilus coloradensis (Banks) are figured and the female is described. Some comments regarding the larvae of Allomyia ( Imania ) are presented. 相似文献
45.
46.
Two new phenotypes of Aspergillus flavus which exhibit novel patterns of aflatoxin production have been identified and characterized. In one of the new variants of A. flavus, aflatoxin is made in the absence of carbohydrate and concomitantly with growth, without a lag period. A second variant did not produce aflatoxin in the presence or absence of carbohydrate. Chemical mutagenesis of this nonaflatoxigenic strain resulted in mutant strains which produced aflatoxin on carbohydrate-containing media. The aflatoxin production pattern observed in these mutants resembled the typical production scheme, with a lag period through log phase growth. 相似文献
47.
The Bloom's syndrome helicase suppresses crossing over during homologous recombination 总被引:1,自引:0,他引:1
Mutations in BLM, which encodes a RecQ helicase, give rise to Bloom's syndrome, a disorder associated with cancer predisposition and genomic instability. A defining feature of Bloom's syndrome is an elevated frequency of sister chromatid exchanges. These arise from crossing over of chromatid arms during homologous recombination, a ubiquitous process that exists to repair DNA double-stranded breaks and damaged replication forks. Whereas crossing over is required in meiosis, in mitotic cells it can be associated with detrimental loss of heterozygosity. BLM forms an evolutionarily conserved complex with human topoisomerase IIIalpha (hTOPO IIIalpha), which can break and rejoin DNA to alter its topology. Inactivation of homologues of either protein leads to hyper-recombination in unicellular organisms. Here, we show that BLM and hTOPO IIIalpha together effect the resolution of a recombination intermediate containing a double Holliday junction. The mechanism, which we term double-junction dissolution, is distinct from classical Holliday junction resolution and prevents exchange of flanking sequences. Loss of such an activity explains many of the cellular phenotypes of Bloom's syndrome. These results have wider implications for our understanding of the process of homologous recombination and the mechanisms that exist to prevent tumorigenesis. 相似文献
48.
McClelland M Sanderson KE Clifton SW Latreille P Porwollik S Sabo A Meyer R Bieri T Ozersky P McLellan M Harkins CR Wang C Nguyen C Berghoff A Elliott G Kohlberg S Strong C Du F Carter J Kremizki C Layman D Leonard S Sun H Fulton L Nash W Miner T Minx P Delehaunty K Fronick C Magrini V Nhan M Warren W Florea L Spieth J Wilson RK 《Nature genetics》2004,36(12):1268-1274
Salmonella enterica serovars often have a broad host range, and some cause both gastrointestinal and systemic disease. But the serovars Paratyphi A and Typhi are restricted to humans and cause only systemic disease. It has been estimated that Typhi arose in the last few thousand years. The sequence and microarray analysis of the Paratyphi A genome indicates that it is similar to the Typhi genome but suggests that it has a more recent evolutionary origin. Both genomes have independently accumulated many pseudogenes among their approximately 4,400 protein coding sequences: 173 in Paratyphi A and approximately 210 in Typhi. The recent convergence of these two similar genomes on a similar phenotype is subtly reflected in their genotypes: only 30 genes are degraded in both serovars. Nevertheless, these 30 genes include three known to be important in gastroenteritis, which does not occur in these serovars, and four for Salmonella-translocated effectors, which are normally secreted into host cells to subvert host functions. Loss of function also occurs by mutation in different genes in the same pathway (e.g., in chemotaxis and in the production of fimbriae). 相似文献
49.
Many lines of evidence indicate that genetically distinct subtypes of motor neurons are specified during development, with each type having characteristic properties of axon guidance and cell-body migration. Motor neuron subtypes express unique combinations of LIM-type homeodomain factors that may act as intrinsic genetic regulators of the cytoskeletal events that mediate cell migration, axon navigation or both. Although experimentally displaced motor neurons can pioneer new routes to their targets, in many cases the axons of motor neurons in complete isolation from their normal territories passively follow stereotypical pathways dictated by the environment. To investigate the nonspecific versus genetically controlled regulation of motor connectivity we forced all motor neurons to express ectopically a LIM gene combination appropriate for the subgroup that innervates axial muscles. Here we show that this genetic alteration is sufficient to convert the cell body settling pattern, gene-expression profile and axonal projections of all motor neurons to that of the axial subclass. Nevertheless, elevated occupancy of the axial pathway can override their genetic program, causing some axons to project to alternative targets. 相似文献
50.
North TE Goessling W Walkley CR Lengerke C Kopani KR Lord AM Weber GJ Bowman TV Jang IH Grosser T Fitzgerald GA Daley GQ Orkin SH Zon LI 《Nature》2007,447(7147):1007-1011