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排序方式: 共有251条查询结果,搜索用时 15 毫秒
1.
2.
Evidence for a role of protein kinase C zeta subspecies in maturation of Xenopus laevis oocytes. 总被引:4,自引:1,他引:3
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I Dominguez M T Diaz-Meco M M Municio E Berra A García de Herreros M E Cornet L Sanz J Moscat 《Molecular and cellular biology》1992,12(9):3776-3783
A number of studies have demonstrated the activation of phospholipase C-mediated hydrolysis of phosphatidylcholine (PC-PLC) both by growth factors and by the product of the ras oncogene, p21ras. Evidence has been presented indicating that the stimulation of this phospholipid degradative pathway is sufficient to activate mitogenesis in fibroblasts as well as that it is sufficient and necessary for induction of maturation in Xenopus laevis oocytes. However, the mechanism whereby PC-PLC transduces mitogenic signals triggered by growth factors or oncogenes remains to be elucidated. In this study, data are presented that show the involvement of protein kinase C zeta subspecies in the channelling of the mitogenic signal activated by insulin-p21ras-PC-PLC in Xenopus oocytes as well as the lack of a critical role of protein kinase C isotypes alpha, beta, gamma, delta, and epsilon in these pathways. 相似文献
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Plasmid pSC101 harbors a recombination site, psi, which is able to resolve plasmid multimers and to substitute for the analogous chromosomal Escherichia coli site dif. 总被引:12,自引:5,他引:7
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Plasmid pSC101 harbors a 28-bp sequence which is homologous to dif, the target site of the XerC/XerD-dependent recombination system in Escherichia coli. Using a technique which allows very sensitive detection of plasmid loss, we show that recombination at this site, termed psi for pSC101 stabilized inheritance, causes a moderate increase in pSC101 stability. The role of the psi sequence in site-specific recombination has been explored in two other contexts. It was cloned in a derivative of plasmid p15A and inserted into the chromosome in place of dif. In the first situation, psi activity requires accessory sequences and results in multimer resolution; in the second situation, it suppresses the effects of the dif deletion and can promote intermolecular exchanges. Thus, psi is a site whose recombinational activity depends on the context, the first in the cer/dif family known to exhibit such flexibility. 相似文献
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Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
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7.
Unraveling a Region-Specific Hyper-Recombination Phenomenon: Genetic Control and Modalities of Terminal Recombination in Escherichia Coli 总被引:2,自引:0,他引:2
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The propensity of the terminus of the Escherichia coli chromosome for recombination has been further explored, using a test based on the selectable loss of a λ prophage inserted between repeated sequences from Tn10. Terminal recombination appears region-specific and unrelated to replication termination in a strain harboring a major chromosomal rearrangement. It requires RecBC(D) activity and must therefore occur between sister chromosomes, to conserve genomic integrity in spite of DNA degradation by RecBCD. Terminal recombination is maximal in the dif region and its intensity on either side of this recombination site depends on the orientation of the repeated sequences, probably because of the single χ site present in each repeat. Additional observations support the model that the crossover is initiated by single-strand invasion between sister chromosomes followed by RecBCD action as a consequence of DNA breakage due to the initial invasion event. Crossover location within repeats inserted at dif position supports the possibility that sister chromosomes are tightly paired in the centre of the terminal recombination zone. These data reinforce the model that postreplicative reconstruction of nucleoid organization creates a localized synapsis between the termini of sister chromosomes. 相似文献
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F Cornet A Scheen J Juchmes A Cession-Fossion 《Comptes rendus des séances de la Société de biologie et de ses filiales》1978,172(3):569-574
The slow increase in heart rate which is observed in normal man submitted to heavy muscular exercise is due for a part to an activation of orthosympathetic cardiac activity which is blocked by beta antagonists. It is also explained by direct action of hyperthermia on the heart. 相似文献
10.
Modulation of interleukin 2 internalization and interleukin 2-dependent cell growth by antireceptor antibodies 总被引:2,自引:0,他引:2
V Duprez M Ferrer V Cornet D Olive A Dautry-Varsat 《The Journal of biological chemistry》1991,266(3):1497-1501
The growth factor interleukin 2 (IL2) binds to and is internalized together with high-affinity surface receptors present on lymphoid cells. This endocytosis thus results in down-regulation of the receptors. However, it is not known if the internalization is relevant to the induction of cell growth. In the present study a rat monoclonal antibody to the P55 chain of the IL2 receptor was used to examine the role of receptor internalization in the IL2-dependent autocrine human tumor T cell line IARC 301. When given alone, this antibody did not inhibit IL2 binding, internalization, or IL2-dependent cell proliferation. However, crosslinking by anti-rat immunoglobulins, which did not affect binding of the growth factor, inhibited both IL2 internalization and cell proliferation. Besides offering a novel means for the specific inhibition of the uptake of IL2 bound to IL2 high-affinity receptors, the results are compatible with the association of this receptor-ligand uptake to the growth stimulation by IL2. 相似文献