Search results for "mutant"
showing 10 items of 670 documents
The human p53 gene mutated at position 249per se is not sufficient to immortalize human liver cells
1999
A particular point mutation of the tumor suppressor gene p53, namely a G→T transversion at the third base of codon 249, is frequently detected in primary hepatocellular carcinomas from patients living in areas where the levels of dietary exposure to aflatoxin B 1 and the rates of infection with the hepatitis B virus are very high. Very recently, a nontumorigenic liver epithelial cell line (HACL-1) with a finite life-span and expressing a number of hepatocyte-specific markers was established from a human hepatocellular adenoma in our laboratory. To analyze the role of mutated p53 in the immortalization of human liver cells, we transfected HACL-1 cells with an expression vector containing a h…
The Mutation without childrenrgl Causes Ecdysteroid Deficiency in Third-Instar Larvae of Drosophila melanogaster
2000
Larvae homozygous for the recessive lethal allele without children(rgl) (woc(rgl)) fail to pupariate. Application of exogenous 20-hydroxyecdysone elicits puparium formation and pupation. Ecdysteroid titer measurements on mutant larvae show an endocrine deficiency in the brain-ring gland complex, which normally synthesizes ecdysone, resulting in a failure of the larvae to achieve a threshold whole body hormone titer necessary for molting. Ultrastructural investigation revealed extensive degeneration of the prothoracic cells of the ring gland in older larvae. The woc gene, located in polytene chromosomal region 97F, consists of 11 exons. A 6.8-kb transcript is expressed throughout development…
The Rate and Molecular Spectrum of Spontaneous Mutations in Arabidopsis thaliana
2010
Evolution in Action Rates of evolution in gene and genome sequences have been estimated, but these estimates are subject to error because many of the steps of evolution over the ages are not directly measurable or are hidden under subsequent changes. Ossowski et al. (p. 92 ) now provide a more accurate measurement of how often spontaneous mutations arise in a nuclear genome. Mutations arising over 30 generations were compared by sequencing DNA from individual Arabidopsis thaliana plants. UV- and deamination-induced mutagenesis appeared to bias the type of mutations found.
Targeted disruption of the peroxisomal thiolase B gene in mouse: a new model to study disorders related to peroxisomal lipid metabolism
2004
The peroxisomal beta-oxidation system consists of four steps catalysed by three enzymes: acyl-CoA oxidase, 3-hydroxyacyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (multifunctional enzyme) and thiolase. In humans, thiolase activity is encoded by one gene, whereas in rodents, three enzymes encoded by three distinct genes (i.e. thiolase A, thiolase B and SCP2/thiolase) catalyse the thiolase activity. So far, acyl-CoA oxidase- and multifunctional enzyme-deficient patients have been identified and knock-out mice for these genes have been produced. Conversely, no isolated thiolase-deficient patient has been found, and no thiolase (A or B)-deficient mice have been generated. Hence, to better u…
Suppression of humoral immune response against herpes simplex virus induced by defective strains, ts- and TK- mutants.
1988
Suppression of humoral antibody formation against HSV is not only induced by replicating Herpes simplex virus type 2 (HSV-2) but also by the defective strain ANG and the deletion mutant 1301 of Herpes simplex virus type 1 (HSV-1). Moreover, ts-mutants A, H, K, S, 1201 and 1208 of HSV-1 as well as some ts-mutants of HSV-2 and “defective-interfering” particles of HSV-1 after high multiplicity of infection-passages induced suppression. Treatment of infected mice with ACG reduced antibody-formation but did not result in suppression. UV-irradiation of the antibody producing strain Len of HSV-1 strongly reduces antibody formation and induces suppression. Experiments using a series of intertypic r…
Impact of a Three Amino Acid Deletion in the CH2 Domain of Murine IgG1 on Fc-Associated Effector Functions
2008
Abstract Four murine IgG subclasses display markedly different Fc-associated effector functions because of their differential binding to three activating IgG Fc receptors (FcγRI, FcγRIII, and FcγRIV) and C1q. Previous analysis of IgG subclass switch variants of 34-3C anti-RBC monoclonal autoantibodies revealed that the IgG1 subclass, which binds only to FcγRIII and fails to activate complement, displayed the poorest pathogenic potential. This could be related to the presence of a three amino acid deletion at positions 233–235 in the CH2 domain uniquely found in this subclass. To address this question, IgG1 insertion and IgG2b deletion mutants at positions 233–235 of 34-3C anti-RBC Abs were …
Relative involvement of nitrate and nitrite reduction in the competitiveness of Pseudomonas fluorescens in the rhizosphere of maize under non-limitin…
2002
Competition between different isogenic mutants of Pseudomonas fluorescens unable to carry out the first steps of the denitrification pathway was compared in soil micro-columns non-planted or planted with maize. A new isogenic mutant of P. fluorescens YT101 affected in both nitrate and nitrite respirations was constructed and used as a model of non-denitrifying strain (FM69MS strain). The outcome of the selection exerted by the plant after co-inoculation of FM69MS at the same ratio either with an isogenic denitrifier unable to reduce nitrate (Nar(-) mutant) or with an isogenic NO2 (-) accumulator (Nir(-) mutant) was investigated in non-limiting NO3 (-) conditions. Regardless of the inoculate…
Room temperature crystal structure of the fast switching M159T mutant of the fluorescent protein dronpa
2015
The fluorescent protein Dronpa undergoes reversible photoswitching reactions between the bright ‘on’ and dark ‘off’ states via photoisomerisation and proton transfer reactions. We report the room temperature crystal structure of the fast switching Met159Thr mutant of Dronpa at 2.0 A resolution in the bright on state. Structural differences with the wild type include shifted backbone positions of strand β8 containing Thr159 as well as an altered A-C dimer interface involving strands β7, β8, β10, and β11. The Met159Thr mutation increases the cavity volume for the p-hydroxybenzylidene-imidazolinone chromophore as a result of both the side chain difference and the backbone positional difference…
Fungal genes related to calcium homeostasis and signalling are upregulated in symbiotic arbuscular mycorrhiza interactions
2012
Fluctuations in intracellular calcium levels generate signalling events and regulate different cellular processes. Whilst the implication of Ca2+ in plant responses during arbuscular mycorrhiza (AM) interactions is well documented, nothing is known about the regulation or role of this secondary messenger in the fungal symbiont. The spatio-temporal expression pattern of putatively Ca2+-related genes of Glomus intraradices BEG141 encoding five proteins involved in membrane transport and one nuclear protein kinase, was investigated during the AM symbiosis. Expression profiles related to successful colonization of host roots were observed in interactions of G. intraradices with roots of wild-ty…
Woc (without children) gene control of ecdysone biosynthesis in Drosophila melanogaster.
2001
Abstract The first step in ecdysteroidogenesis, i.e. the 7,8-dehydrogenation of dietary cholesterol (C) to 7-dehydrocholesterol (7dC), is blocked in Drosophila melanogaster homozygous woc (without children) third instar larval ring glands (source of ecdysone). Unlike ring glands from wild-type D. melanogaster larvae, glands from woc mutants cannot convert radiolabelled C or 25-hydroxycholesterol (25C) to 7dC or 7-dehydro-25-hydroxycholesterol (7d25C) in vitro, nor to ecdysone (E). Yet, when these same glands are incubated with synthetic tracer 7d25C, the rate of metabolism of this polar Δ5,7-sterol into E is identical to that observed with glands from comparably staged wild-type larvae. The…