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61.
Phosphorylation of GATA-1 increases its DNA-binding affinity and is correlated with induction of human K562 erythroleukaemia cells. 总被引:8,自引:0,他引:8
We have investigated by electrophoretic mobility shift assay (EMSA) the level of GATA-1 DNA-binding activity in nuclear extracts prepared from the human erythroleukaemic cell line, K562, after erythroid induction by hemin, sodium butyrate (NaB) or Trichostatin A or treatment with N -acetylcysteine (NAC). Relative to extract from untreated cells, GATA-1 binding activity increased markedly in all cases. However, immunoblot analysis revealed unchanged levels of GATA-1 protein after induction. Incubation of induced but not uninduced K562 extracts with phosphatase prior to EMSA weakened the binding activity, suggesting that the increase in GATA-1 binding following induction of K562 cells was a consequence of phosphorylation. When the mouse erythroleukaemic cell line MEL was induced with dimethylsulphoxide (DMSO), NaB or NAC, GATA-1 binding activity fell with DMSO, rose significantly with NaB and remained at about the same level in NAC-induced cells. In this case immunoblotting revealed that GATA-1 protein levels were in accord with the EMSA data. The DNA-binding activities of induced and uninduced MEL cell nuclear extracts were decreased by incubation with phosphatase, showing that phosphoryl-ation and DNA binding of GATA-1 are already optimalin these cells. The DNA-binding activity of affinity-purified GATA-1 from MEL cells was also reduced by phosphatase treatment, showing that phosphorylation/dephosphorylation is directly affecting the factor. Furthermore, when a comparison was made by EMSA of nuclear extracts prepared from K562 and MEL cells untreated or incubated with okadaic acid, a phosphatase inhibitor, GATA-1 binding was seen to increase with K562 cells, whereas with MEL cells there was no change in GATA-1 binding. Overall the results suggest that the level of GATA-1 phosphorylation increases after the induction of K562, but not MEL cells, where GATA-1 is already highly phosphorylated. Furthermore, phosphorylation increases the binding affinity of GATA-1 for a canonical binding site. 相似文献
62.
In order to elucidate the nature of the response of potato to impact injury at the biochemical level, changes in the location
of the enzyme responsible for the discoloration, polyphenol oxidase, were determined using immunogold location with an antibody
specific for potato tuber polyphenol oxidase. Tissue printing revealed that the enzyme was distributed throughout the tuber.
Following impact injury, both tissue printing and quantitative electron microscopy indicated that there was no increase in
the level of the enzyme although there was subcellular redistribution of polyphenol oxidase. This redistribution was first
apparent at 12 h after impact, as determined by the use of confocal immunolocation, and coincided with loss of membrane integrity.
These changes were examined in parallel with a number of stress-related parameters in both impact and wound responses. Wounding
was accompanied by active gene expression and protein synthesis, leading to metabolic activity and tissue repair. In contrast,
the bruising response was characterised by a limited active response and vital-staining methods indicated that after 16 h
the tissue undergoes cell death.
Received: 4 June 1998 / Accepted: 18 September 1998 相似文献
63.
64.
Kappa-chain constant-region gene sequences in genus Rattus: coding regions are diverging more rapidly than noncoding regions 总被引:2,自引:0,他引:2
We have determined the nucleotide sequence of a 1,200-base pair (bp)
genomic fragment that includes the kappa-chain constant-region gene (C
kappa) from two species of native Australian rodents, Rattus leucopus
cooktownensis and Rattus colletti. Comparison of these sequences with each
other and with other rodent C kappa genes shows three surprising features.
First, the coding regions are diverging at a rate severalfold higher than
that of the nearby noncoding regions. Second, replacement changes within
the coding region are accumulating at a rate at least as great as that of
silent changes. Third, most of the amino acid replacements are localized in
one region of the C kappa domain--namely, the carboxy-terminal "bends" in
the alpha-carbon backbone. These three features have previously been
described from comparisons of the two allelic forms of C kappa genes in R.
norvegicus. These data imply the existence of considerable evolutionary
constraints on the noncoding regions (based on as yet undetermined
functions) or powerful positive selection to diversify a portion of the
constant-region domain (whose physiological significance is not known).
These surprising features of C kappa evolution appear to be characteristic
only of closely related C kappa genes, since comparison of rodent with
human sequences shows the expected greater conservation of coding regions,
as well as a predominance of silent nucleotide substitutions within the
coding regions.
相似文献
65.
J. W. Daly E. McNeal C. Partington M. Neuwirth C. R. Creveling 《Journal of neurochemistry》1980,35(2):326-337
Norepinephrine, histamine, adenosine, glutamate, and depolarizing agents elicit accumulations of radioactive cyclic AMP from adenine-labeled nucleotides in particulate fractions from Krebs-Ringer homogenates of guinea pig cerebral cortex. The particulate fractions contain sac-like entities, which apparently are associated with a significant portion of the membranal adenylate cyclase. Particulate fractions from sucrose homogenates are a less effective source of such responsive entities. Activation of the adenine-labeled cyclic AMP-generating systems by norepinephrine is by means of alpha-adrenergic receptors, while activation by histamine is through H1- and H2-histaminergic receptors. Adenosine responses are potentiated by the amines and are antagonized by alkylxanthines. Glutamate and depolarizing agents appear to elicit accumulations of cyclic AMP via "release" of endogenous adenosine. It is proposed, based on the virtual absence of an alpha-adrenergic or H1-histaminergic response in the presence of a combination of potent adenosine and H2-histaminergic antagonists, that alpha-adrenergic and H1-histaminergic receptor mechanisms do not activate adenylate cyclase directly in brain slices or Krebs-Ringer particulate fractions, but merely facilitate activation by beta-adrenergic, H2-histaminergic, or adenosine receptors. 相似文献
66.
67.
G. de B. Mitford-Barberton P. S. Andrews H. J. Voss L. R. MacLean Patricia E. Wallace E. G. Hadaway D. E. Sibson J. M. Ritchie B. K. Samtani I. S. Hodgson-Jones A. B. Jones T. H. Cullen P. Willis R. M. Ingram G. Gerrard Thomas Partington T. C. Beer J. R. Pettman Geoffrey Baines 《BMJ (Clinical research ed.)》1974,4(5944):594
68.
S Franz Bender Faline Plantenga Albrecht Neftel Markus Jocher Hans-Rudolf Oberholzer Luise K?hl Madeline Giles Tim J Daniell Marcel GA van der Heijden 《The ISME journal》2014,8(6):1336-1345
N2O is a potent greenhouse gas involved in the destruction of the protective ozone layer in the stratosphere and contributing to global warming. The ecological processes regulating its emissions from soil are still poorly understood. Here, we show that the presence of arbuscular mycorrhizal fungi (AMF), a dominant group of soil fungi, which form symbiotic associations with the majority of land plants and which influence a range of important ecosystem functions, can induce a reduction in N2O emissions from soil. To test for a functional relationship between AMF and N2O emissions, we manipulated the abundance of AMF in two independent greenhouse experiments using two different approaches (sterilized and re-inoculated soil and non-mycorrhizal tomato mutants) and two different soils. N2O emissions were increased by 42 and 33% in microcosms with reduced AMF abundance compared to microcosms with a well-established AMF community, suggesting that AMF regulate N2O emissions. This could partly be explained by increased N immobilization into microbial or plant biomass, reduced concentrations of mineral soil N as a substrate for N2O emission and altered water relations. Moreover, the abundance of key genes responsible for N2O production (nirK) was negatively and for N2O consumption (nosZ) positively correlated to AMF abundance, indicating that the regulation of N2O emissions is transmitted by AMF-induced changes in the soil microbial community. Our results suggest that the disruption of the AMF symbiosis through intensification of agricultural practices may further contribute to increased N2O emissions. 相似文献
69.
目的:比较不同时期颈髓损伤的MRI表现及DTI的应用价值。方法:收集急性颈髓压迫病例15例、慢性颈髓压迫病例23例、颈髓慢性压迫合并急性压迫病例12例。15例健康志愿者作为对照组。进行常规MRI检查,应用DTI检查测量表现扩散系数(ADC)值和各向异性分数(FA)。比较各组间ADC值和FA值,并进行统计学分析。结果:急性颈髓迫病例,常规MRI显示颈髓增粗,呈等T1长T2信号;慢性颈髓压迫病例,9例呈长T1长T2信号,14例呈等T1长T2信号;慢性颈髓压迫并急性压迫病例颈髓明显增粗,呈等、长T1明显长T2信号。与对照组比较:急性颈髓压迫组的ADC值和FA值均明显降低,两组的差异有显著性;慢性颈髓压迫组的FA值降低,ADC值增高,两组的差异有显著性;慢性脊髓压迫合并急性脊髓压迫组ADC值与对照组比较无差异,FA值低于对照组。颈髓压迫各组间ADC值及FA值比较差异显著。结论:不同时期颈髓损伤常规MRI图像缺乏特异性,根据ADC值及FA值可判断颈髓损伤的时期。 相似文献
70.