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61.
Stoichiometry of cellular and viral components in the polyomavirus middle-T antigen-tyrosine kinase complex. 总被引:8,自引:0,他引:8 下载免费PDF全文
S H Cheng P C Espino J Marshall R Harvey A E Smith 《Molecular and cellular biology》1990,10(10):5569-5574
Our results indicate that only one type of tyrosine kinase is present within each middle-T antigen-tyrosine kinase complex, suggesting that middle-T antigen forms separate complexes with different tyrosine kinases. Furthermore, we determined that there is only one molecule of middle-T antigen within any one of these complexes. We interpret this to mean that in any given cell, polyomavirus transformation involves, at least in part, the simultaneous deregulation of a number of separate pathways controlling cellular proliferation. Finally, we also demonstrate that the separate middle-T:pp60c-src and middle-T:pp59c-fyn complexes are each able to interact with the same cellular p81/85-kDa phosphoprotein, a possible component of the phosphatidylinositol kinase. 相似文献
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64.
本文以普通小麦(Triticum aestivum L.)根端分生组织为材料,在透射电镜下对间期细胞核内的集缩染色质的高层次结构进行了研究。在其中观察到直径约为20—25nm、50nm及110—120nm 的不同等级染色线,并且发现直径110—120nm 的染色线是由50nm 的染色线组成的,而直径约50nm 的染色线是由20—25nm 的染色线组成的。对这三个层次染色质结构之间的集缩方式进行了讨论。 相似文献
65.
用酸浸提、酒精沉淀法,从桔皮中提取果胶,通过正交设计分析,获得最佳得率的工艺条件。即果胶浸提液的酸度为pH2,反应时间2小时。沉淀果胶的酒精浓度为50%,其得率是12.6%。 相似文献
66.
桂西壮族手皮纹的分析 总被引:4,自引:0,他引:4
本文对广西西部500例健康壮族大、中学生的手皮纹进行了观察分析,计算出各型指纹频率、指纹脊线总数、指纹频度指数、atd角度、a-b脊线数、τ距比、主线横向指数、皮纹花样出现率、掌褶纹出现率共九项基本参数,并将这些数值与汉族作了比较,桂西壮族的手纹与汉族既有相似之处,又有本民族的特点。 相似文献
67.
利用与β地中海贫血致病基因连锁的遗传标记进行产前诊断已成为可能,但群体中遗传标记与致病基因的不完全连锁决定了产前诊断的局限性。根据中国人群中7个遗传标记的多态性分布数据,我们计算了各遗传标记及其所有组合的可诊断率。又据各遗传标记及其组合的可诊断率,我们可以对:(1)所作出产前诊断的可诊断率进行预先评价;(2)选择适合于中国人群β地中海贫血产前诊断的最佳策略。本文提出了中国人群中选择遗传标记进行β地中海贫血产前诊断的最佳路线。同时将基因的连锁分析法与寡核苷酸法进行了比较。 相似文献
68.
Macrophage precursors as natural killer cells against tumor cells and microorganisms 总被引:4,自引:0,他引:4
M Baccarini L Hao T Decker M L Lohmann-Matthes 《Natural immunity and cell growth regulation》1988,7(5-6):316-327
Macrophage precursors cells have been isolated from spleen and liver of mice and have characterized using F4/80 antibody, their proliferative response to CSF-1 and their maturation to macrophages. These nonadherent and nonphagocytic cells exert strong killing of Yac-1 tumor cells and of various microorganisms. Transplantation of these macrophage precursors into lethally irradiated allogenic hosts restores natural killer (NK) activity within 14 days. Macrophage precursors show enhanced NK activity when activated with interleukin 2. FACS analysis of F 4/80 presorted macrophage precursors reveals about 30% of the cells coexpressing NK 1.1. and F 4/80. These data support the assumption that at least a part of the NK cell compartment is derived from the myeloid lineage. 相似文献
69.
The carboxy terminus of pp60c-src is a regulatory domain and is involved in complex formation with the middle-T antigen of polyomavirus. 总被引:19,自引:7,他引:12 下载免费PDF全文
S H Cheng H Piwnica-Worms R W Harvey T M Roberts A E Smith 《Molecular and cellular biology》1988,8(4):1736-1747
A large number of mutations were introduced into the carboxy-terminal domain of pp60c-src. The level of phosphorylation on Tyr-416 and Tyr-527, the transforming activity (as measured by focus formation on NIH 3T3 cells), kinase activity, and the ability of the mutant pp60c-src to associate with the middle-T antigen of polyomavirus were examined. The results indicate that Tyr-527 is a major carboxy-terminal element responsible for regulating pp60c-src in vivo. A good but not perfect correlation exists between lack of phosphorylation at Tyr-527 and increased phosphorylation at Tyr-416, between elevated phosphorylation on Tyr-416 and activated kinase activity, and between activated kinase activity and transforming activity. Phosphorylation of Tyr-527 was insensitive to the mutation of adjacent residues, indicating that the primary sequence only has a minor role in recognition by kinases or phosphatases which regulate it in vivo. Three mutants which have in common a modified Glu-524 residue were phosphorylated on Tyr-416 and Tyr-527 and were weakly transforming. This suggests that other mechanisms besides complete dephosphorylation of Tyr-527 can lead to increased phosphorylation of Tyr-416 and activation of the transforming activity of pp60c-src. Furthermore, the residues between Asp-518 and Pro-525 were required to form a stable complex with middle-T antigen. The proximity of these sequences to Tyr-527 suggests a model in which middle-T activates pp60c-src by binding directly to this region of the molecular and thereby preventing phosphorylation of Tyr-527. Alternatively, middle-T binding may mediate a conformational change in this region, which in turn induces an alteration in the level of phosphorylation at Tyr-527 and Tyr-416. 相似文献
70.
Identification of genes required for cytoplasmic localization in early C. elegans embryos 总被引:18,自引:0,他引:18
We have isolated and analyzed eight strict maternal effect mutations identifying four genes, par-1, par-2, par-3, and par-4, required for cytoplasmic localization in early embryos of the nematode C. elegans. Mutations in these genes lead to defects in cleavage patterns, timing of cleavages, and localization of germ line-specific P granules. Four mutations in par-1 and par-4 are fully expressed maternal effect lethal mutations; all embryos from mothers homozygous for these mutations arrest as amorphous masses of differentiated cells but are specifically lacking intestinal cells. Four mutations in par-2, par-3, and par-4 are incompletely expressed maternal effect lethal mutations and are also grandchildless; some embryos from homozygous mothers survive and grow to become infertile adults due to absence of functional germ cells. We propose that all of these defects result from the failure of a maternally encoded system for intracellular localization in early embryos. 相似文献