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21.
M Uzan Y d'Aubenton-Carafa R Favre V de Franciscis E Brody 《The Journal of biological chemistry》1985,260(1):633-639
Middle-mode RNA synthesis in T4-infected cells takes place before replication of phage DNA commences. What distinguishes it from early-mode RNA synthesis is that initiation of middle RNA depends on T4-coded proteins, in particular on the mot gene product. mot protein is localized in a DNA-protein complex which forms during the first few minutes of infection. All of the cell's mot protein is bound in this complex, and it continues to be bound long after the synthesis of mot protein has stopped. When we infect Escherichia coli with T4 carrying a temperature-sensitive mutation in the mot gene, we find a correlation between the physiology of this mot mutant and the amount of mot protein bound in the DNA-protein complex. Although there is some host RNA polymerase in the complex, mot protein does not seem to bind to this enzyme. Two other T4-coded proteins, of molecular weights 17,600 and 15,000, are also found in the pre-replicative DNA-protein complex. One of these, p17,600, is coded for by a 750-base pair region located between genes 39 and 56; p17,600 appears to be the recently described motB gene product. The other protein, p15,000, is not an RNA polymerase-binding protein; it is characterized by its strong binding to the DNA-protein complex. 相似文献
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A one-step clearing and embedding procedure for alizarin red S stained skeletons is described. Embryos are fixed in formalin, skinned and eviscerated. After staining in a 10 mg/liter solution of alizarin red S in 5% aqueous KOH, specimens are dehydrated in a graded series of acetone-polyester monomer solutions. Finally, the specimens are embedded at room temperature in the polyester resin. A special reusable metallic mold is described for embedment of large fetuses. Specimens previously cleared in glycerol can be processed with this method. 相似文献
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Effect of human T-cell leukemia virus type I tax protein on activation of the human vimentin gene. 总被引:28,自引:9,他引:19 下载免费PDF全文
We report that the expression of the vimentin gene, a cytoskeletal growth-regulated gene, is activated in trans by the Tax (p40x) transactivator protein encoded by the human T-cell leukemia virus type I. Expression of the Tax protein activates a number of cellular genes, such as those coding for the alpha chain of the high-affinity interleukin-2 receptor and interleukin-2. These findings indicate that the Tax protein is involved in the unregulated T-cell growth associated with human T-cell leukemia virus type I infection. Higher levels of vimentin mRNA were expressed in two human T-cell leukemia virus type I-transformed T cell lines, C91/PL and C81-66/45, when compared with that in Jurkat T cells. We demonstrate that this activation is conferred by the vimentin upstream flanking sequences. Indeed, enhanced activity was detected when constructs with the vimentin promoter linked to the chloramphenicol acetyltransferase gene were transfected in HeLa cells and in two cell lines of hematopoietic origin (Jurkat T lymphoblastoid cells and U937 promonocytic cells) together with a Tax expression plasmid. By introducing a series of deletions in the vimentin promoter, we further restrict these sequences to 30 base pairs, located between 241 and 210 base pairs upstream of the mRNA cap site. A 40-base-pair oligonucleotide containing this regulatory region proved sufficient to confer Tax inducibility upon a heterologous promoter linked to chloramphenicol acetyltransferase. Importantly, this segment includes an 11-base-pair promoter segment that has homology with the binding site for the NF-kappa B transactivating factor. Our findings indicate that constitutive expression of the vimentin gene under the control of the Tax protein may be relevant in understanding the progression of the lymphoproliferative process associated with human T-cell leukemia virus type I infection. 相似文献
25.
James R. Anderson Catherine Fritsch Bernadette Favre 《Primates; journal of primatology》1990,31(4):611-615
An adult femaleLemur catta and an adult femaleEulemur fulvus were given edible rewards for scratching. Both subjects learned to scratch in order to obtain the rewards, showed diminished
rates of scratching during periods of extinction, and learned to scratch preferentially with one foot when required. TheLemur catta subject was more responsive to the changing experimental conditions than theEulemur fulvus. The conditionability of scratching in primates does not appear to be directly related to the widespread occurrence of scratching
in simian social contexts. 相似文献
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Summary Direct measurements of membrane fluidity by fluorescence anisotropy of protoplasts fromKloeckera apiculata andSaccharomyces cerevisiae, a low and a high ethanol tolerant strain respectively, are presented. The comparison of the behaviour of the two strains
grown with or without ethanol enabled us to demonstrate the existing relationship between ethanol tolerance and membrane fluidity. 相似文献
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Abstract. A considerable interest exists worldwide in the development of live attenuated oral vaccines against diarrhoeal diseases. In addition to vaccination against the corresponding pathogens, such vaccine strains can be used as carriers for the expression of protective antigens from other organisms. The antigenic repertoire of a given vaccine strain may thereby be extended, potentially leading to a bivalent vaccine. The lipopolysaccharide is known to be a major antigenic surface component of bacterial enteric pathogens. The feasibility of the development of combined vaccines based on live attenuated carriers expressing two O-serotype specificities is illustrated here by the development of candidate live oral vaccines against Shigella sonnei using Salmonella typhi and Vibrio cholerae as carriers. Various factors that may limit the potential of such hybrid strains as bivalent vaccines are discussed. 相似文献
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