共查询到20条相似文献，搜索用时 62 毫秒
1.
Effect of phospholipase C-gamma overexpression on PDGF-induced second messengers and mitogenesis 总被引：24，自引：0，他引：24
B Margolis A Zilberstein C Franks S Felder S Kremer A Ullrich S G Rhee K Skorecki J Schlessinger 《Science (New York, N.Y.)》1990,248(4955):607-610
Platelet-derived growth factor (PDGF) stimulates phospholipase C (PLC) activity and the phosphorylation of the gamma isozyme of PLC (PLC-gamma) in vitro and in living cells. The role of PLC-gamma in the phosphoinositide signaling pathway was addressed by examining the effect of overexpression of PLC-gamma on cellular responses to PDGF. Overexpression of PLC-gamma correlated with PDGF-induced tyrosine phosphorylation of PLC-gamma and with PDGF-induced breakdown of phosphatidylinositol 4,5-bisphosphate (PIP2). However, neither bradykinin- nor lysophosphatidic acid-induced phosphoinositide metabolism was enhanced in the transfected cells, suggesting that the G protein-coupled phosphoinositide responses to these ligands are mediated by other PLC isozymes. The enhanced PDGF-induced generation of inositol trisphosphate (IP3) did not enhance intracellular calcium signaling or influence PDGF-induced DNA synthesis. Thus, enzymes other than PLC-gamma may limit PDGF-induced calcium signaling and DNA synthesis. Alternatively, PDGF-induced calcium signaling and DNA synthesis may use biochemical pathways other than phosphoinositide metabolism for signal transduction. 相似文献
2.
PDGF-induced activation of phospholipase C is not required for induction of DNA synthesis 总被引：14，自引：0，他引：14
T D Hill N M Dean L J Mordan A F Lau M Y Kanemitsu A L Boynton 《Science (New York, N.Y.)》1990,248(4963):1660-1663
Platelet-derived growth factor (PDGF) induction of DNA synthesis is believed to involve activation of phospholipase C (PLC) and subsequent accumulation of inositol 1,4,5-triphosphate [I(1,4,5)P3], increase in intracellular Ca2+, activation of protein kinase C (PKC), and receptor down regulation. Generation of these events is triggered by the tyrosine protein kinase (TPK) activity of the PDGF receptor. The TPK inhibitor genistein blocked PDGF induction of these events, including DNA synthesis, with the exception of receptor down regulation. PDGF-induced phosphotyrosine phosphorylations, including receptor autophosphorylation, were inhibited by genistein. Removal of genistein and PDGF resulted in DNA synthesis without the occurrence of PLC activation. These findings indicate that these early events, with the exception of receptor down regulation, are not necessary for PDGF-induced DNA synthesis. 相似文献
3.
Activation of the cellular proto-oncogene product p21Ras by addition of a myristylation signal 总被引：30，自引：0，他引：30
J E Buss P A Solski J P Schaeffer M J MacDonald C J Der 《Science (New York, N.Y.)》1989,243(4898):1600-1603
The 21-kD proteins encoded by ras oncogenes (p21Ras) are modified covalently by a palmitate attached to a cysteine residue near the carboxyl terminus. Changing cysteine at position 186 to serine in oncogenic forms produces a nonpalmitylated protein that fails to associate with membranes and does not transform NIH 3T3 cells. Nonpalmitylated p21Ras derivatives were constructed that contained myristic acid at their amino termini to determine if a different form of lipid modification could restore either membrane association or transforming activity. An activated p21Ras, altered in this way, exhibited both efficient membrane association and full transforming activity. Surprisingly, myristylated forms of normal cellular Ras were also transforming. This demonstrates that Ras must bind to membranes in order to transmit a signal for transformation, but that either myristate or palmitate can perform this role. However, the normal function of cellular Ras is diverted to transformation by myristate and therefore must be regulated ordinarily by some unique property of palmitate that myristate does not mimic. Myristylation thus represents a novel mechanism by which Ras can become transforming. 相似文献
4.
参照GenBank上已发表的鸡白细胞介素2序列设计引物,运用RT-PCR技术,从经ConA诱导的 20～35日龄固始鸡脾细胞总RNA中扩增出目的片段,IL-2基因,将其插入到pGEM-T载体上,构建了克隆质粒 pGEM-T-chIL-2。测序结果表明,本试验克隆的固始鸡白细胞介素2基因与GenBank上已发表的序列相比,存在2 个核苷酸变异。重新设计表达引物,以克隆质粒pGEM-T—chIL一2为模板PCR扩增表达片段,对表达片段进行 Hind Ⅲ和BamH Ⅰ双酶切,连接到作同样双酶切的pET28a表达载体上,鉴定后转化大肠杆菌BL21并进行IPTG 诱导表达,然后对表达产物进行SDS-PAGE电泳鉴定,结果表明,表达蛋白主要以包涵体的形式存在,表达蛋白分子质量约为18 ku;目的蛋白表达量占总量的18％。体外活性检测表明,重组蛋白具有促进淋巴细胞增殖的活性。 相似文献
5.
利用PCR技术,从E.coli C83902中扩增出不含信号肽序列的K88ac菌毛蛋白亚基基因片段,将其克隆到表达载体pQE-30中,构建了原核表达载体pQE30-K88ac,并转入E.coli XL1-Blue中。经IPTG诱导后,由T5启动子调控表达了氨基端带6个连续组氨酸残基的以包涵体形式存在的K88ac蛋白,在变性条件下对目的蛋白进行纯化,并获得了高纯度的融合蛋白。 相似文献
6.
Microinjected c-myc as a competence factor 总被引：54，自引：0，他引：54
L Kaczmarek J K Hyland R Watt M Rosenberg R Baserga 《Science (New York, N.Y.)》1985,228(4705):1313-1315
While a number of oncogenes are expressed in a cell cycle-dependent manner, their role in the control of cell proliferation can only be established by a direct functional assay. The c-myc protein, upon microinjection into nuclei of quiescent Swiss 3T3 cells, cooperated with platelet-poor plasma in the stimulation of cellular DNA synthesis. This suggests that c-myc protein, like platelet-derived growth factor (PDGF), may act as a competence factor in the cell cycle to promote the progression of cells to S phase. The presence in the medium of an antibody against PDGF abolished DNA synthesis induced by microinjected PDGF; however, the microinjected c-myc protein stimulated DNA synthesis even when its own antibody was present in the medium. The c-myc protein may act as an intracellular competence factor, while PDGF expresses its biological activity only from outside the cells. 相似文献
7.
人朊蛋白基因的克隆与原核表达 总被引：3，自引：1，他引：3
以人血液中提取的总DNA为模板,克隆朊蛋白(prion protein,PrP)基因Prnp户的开放阅读框(ORF),与pMD -18T载体连接后转入E．coli JM109,用Blast软件比较重组质粒序列,结果表明获得的人Prnp的ORF与Genbank登录的相应核苷酸序列最高同源性为99．6％,推导的氨基酸序列同源性为99．8％,将编码人成熟PrP的基因定向克隆到 pET-30a(+)表达载体,将重组质粒pET-homPrP转化E．coli BL21(DE3),在37℃下用1．0 mmol／L IPTG诱导,重组融合蛋白获得高效表达,SDS-PAGE显示表达产物以包涵体形式存在,占菌体总蛋白的20％～25％．用Ni-NTA 树脂亲和层析纯化了表达产物．Western-blotting分析表明,融合蛋白被抗PrP的单克隆抗体特异识别．因此,在大肠杆菌中表达的人成熟PrP融合蛋白可以作为制备PrP抗体的免疫原． 相似文献
8.
为对SARS N蛋白的功能进行研究,并建立快速、方便的诊断方法,将已克隆、构建成功的重组质粒PGEX-4T/N转化至E.coli BL21中,IPTG诱导表达,表达产物与兔源GST多抗在66 kD处有很强的反应性,融合蛋白GST-N分别通过GSTrap FF 1 mL纯化柱和割胶纯化两种方法获得了具有生物活性和变性的融合蛋白.其蛋白浓度分别为0.85 mg/mL和0.433 mg/mL.利用纯化的GST-N蛋白免疫SPF BALB/c小鼠,获得4株能稳定传代并分泌抗SARS N单克隆抗体(mAb)的杂交瘤细胞,分别命名为3E5、6B9、4C2、4B7,经Western blot分析表明,所获得的4株抗SARS N单克隆抗体与纯化的N蛋白均具有特异反应性,且不与禽冠状病毒的N蛋白发生反应. 相似文献
9.
Genetic and pharmacological suppression of oncogenic mutations in ras genes of yeast and humans 总被引：59，自引：0，他引：59
W R Schafer R Kim R Sterne J Thorner S H Kim J Rine 《Science (New York, N.Y.)》1989,245(4916):379-385
The activity of an oncoprotein and the secretion of a pheromone can be affected by an unusual protein modification. Specifically, posttranslational modification of yeast a-factor and Ras protein requires an intermediate of the cholesterol biosynthetic pathway. This modification is apparently essential for biological activity. Studies of yeast mutants blocked in sterol biosynthesis demonstrated that the membrane association and biological activation of the yeast Ras2 protein require mevalonate, a precursor of sterols and other isoprenes such as farnesyl pyrophosphate. Furthermore, drugs that inhibit mevalonate biosynthesis blocked the in vivo action of oncogenic derivatives of human Ras protein in the Xenopus oocyte assay. The same drugs and mutations also prevented the posttranslational processing and secretion of yeast a-factor, a peptide that is farnesylated. Thus, the mevalonate requirement for Ras activation may indicate that attachment of a mevalonate-derived (isoprenoid) moiety to Ras proteins is necessary for membrane association and biological function. These observations establish a connection between the cholesterol biosynthetic pathway and transformation by the ras oncogene and offer a novel pharmacological approach to investigating, and possibly controlling, ras-mediated malignant transformations. 相似文献
10.
Immunochemical proof that a novel rearranging gene encodes the T cell receptor delta subunit 总被引：58，自引：0，他引：58
H Band F Hochstenbach J McLean S Hata M S Krangel M B Brenner 《Science (New York, N.Y.)》1987,238(4827):682-684
The T cell receptor (TCR) delta protein is expressed as part of a heterodimer with TCR gamma, in association with the CD3 polypeptides on a subset of functional peripheral blood T lymphocytes, thymocytes, and certain leukemic T cell lines. A monoclonal antibody directed against TCR delta was produced that binds specifically to the surface of several TCR gamma delta cell lines and immunoprecipitates the TCR gamma delta as a heterodimer from Triton X-100 detergent lysates and also immunoprecipitates the TCR delta subunit alone after chain separation. A candidate human TCR delta complementary DNA clone (IDP2 O-240/38), reported in a companion paper, was isolated by the subtractive library approach from a TCR gamma delta cell line. This complementary DNA clone was used to direct the synthesis of a polypeptide that is specifically recognized by the monoclonal antibody to TCR delta. This complementary DNA clone thus corresponds to the gene that encodes the TCR delta subunit. 相似文献
11.
erbB-2 is a potent oncogene when overexpressed in NIH/3T3 cells 总被引：94，自引：0，他引：94
P P Di Fiore J H Pierce M H Kraus O Segatto C R King S A Aaronson 《Science (New York, N.Y.)》1987,237(4811):178-182
A wide variety of human tumors contain an amplified or overexpressed erbB-2 gene, which encodes a growth factor receptor-like protein. When erbB-2 complementary DNA was expressed in NIH/3T3 cells under the control of the SV40 promoter, the gene lacked transforming activity despite expression of detectable levels of the erbB-2 protein. A further five- to tenfold increase in its expression under influence of the long terminal repeat of Moloney murine leukemia virus was associated with activation of erbB-2 as a potent oncogene. The high levels of the erbB-2 product associated with malignant transformation of NIH/3T3 cells were observed in human mammary tumor cells that overexpressed this gene. These findings demonstrate a new mechanism for acquisition of oncogenic properties by genes encoding growth factor receptor-like proteins and provide a functional basis for the role of their overexpression in the development of human malignancies. 相似文献
12.
The roles of phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC) in chemoattractant-elicited responses were studied in mice lacking these key enzymes. PI3Kgamma was required for chemoattractant-induced production of phosphatidylinositol 3,4,5-trisphosphate [PtdIns (3,4,5)P3] and has an important role in chemoattractant-induced superoxide production and chemotaxis in mouse neutrophils and in production of T cell-independent antigen-specific antibodies composed of the immunoglobulin lambda light chain (TI-IglambdaL). The study of the mice lacking PLC-beta2 and -beta3 revealed that the PLC pathways have an important role in chemoattractant-mediated production of superoxide and regulation of protein kinases, but not chemotaxis. The PLC pathways also appear to inhibit the chemotactic activity induced by certain chemoattractants and to suppress TI-IglambdaL production. 相似文献
13.
HIV-1-infected T cells show a selective signaling defect after perturbation of CD3/antigen receptor 总被引：16，自引：0，他引：16
The binding of antigen or monoclonal antibody to the T cell receptor for antigen or the closely associated CD3 complex causes increases in the concentration of intracellular ionized calcium and subsequent cell proliferation. By measuring second messenger production in primary cultures of human immunodeficiency virus (HIV-1)--infected T cells stimulated with monoclonal antibodies specific for either CD3 or CD2, a specific impairment of membrane signaling was revealed. The HIV-1--infected T cells were unable to mobilize Ca2+ after stimulation with anti-CD3, whereas CD2-induced calcium mobilization remained intact. Furthermore, the HIV-1--infected cells proliferated poorly after CD3 stimulation, although the cells retained normal DNA synthesis in response to interleukin-2 stimulation. These results show that the signals initiated by CD2 and CD3 can be regulated independently within the same T cell; uncoupling of signal transduction after antigen-specific stimulation provides a biochemical mechanism to explain, in part, the profound immunodeficiency of patients with HIV-1 infection. 相似文献
14.
为获得具有抗原性的口蹄疫病毒(FMDV)3D蛋白N端T细胞表位的重组表达蛋白,根据FMDV3D蛋白前115位氨基酸序列,设计优化并人工合成相应的核酸序列,将其克隆至pET-28a中,构建原核表达质粒pET28a-115,并将重组质粒转化至BL21(DE3)细胞。经IPTG诱导后,收集菌液进行SDS-PAGE和Western-bolt鉴定,结果显示,在16kD处有一条明显的蛋白表达条带。对表达产物进行可溶性分析,结果表达蛋白50%为可溶性蛋白,经Ni-NTA亲和层析纯化后获得了较高浓度和纯度的目的蛋白。研究结果表明,含FMDV 3D蛋白前115位氨基酸的重组蛋白在大肠杆菌中得到了高效可溶性表达,并具有较好的抗原活性,为开发口蹄疫诊断试剂和基因工程疫苗奠定了基础。 相似文献
15.
[目的]原核表达热带念珠菌(Candida tropicalis MYA-3404)β-葡聚糖合成酶(KRE9),并进行酶比活力测定,为研究其结构和生物学功能提供参考.[方法]提取热带念珠菌DNA,PCR扩增KRE9基因,构建其原核表达载体pET28a-KRE9后转化大肠杆菌(Escherichia coli)BL21(DE3)感受态细胞,通过IPTG诱导表达及组氨酸(His)标签纯化树脂亲和柱纯化获得融合蛋白KRE9,并利用3,5-二硝基水杨酸(DNS)显色法测定其比活力.[结果]克隆获得的KRE9基因全长816 bp,编码271个氨基酸,与参考基因序列(GenBank登录号XM_002547984)的相似性高达99.75%.将其原核表达载体pET28a-KRE9转化大肠杆菌BL21(DE3)感受态细胞,通过诱导表达及纯化获得重组蛋白KRE9,经SDS-PAGE检测,发现其纯度较高,大小约35 kD.Western blotting鉴定结果显示,重组蛋白KRE9能与抗His抗体发生特异性结合.重组蛋白KRE9比活力为9.169×104U/mg.[结论]重组蛋白KRE9具有良好的特异性和较高β-葡聚糖合成酶活性,可用于其结构和生物学功能研究. 相似文献
16.
为获得Eno的重组蛋白,采用PCR法从金黄色葡萄球菌wood46株基因组扩增eno基因,并连接到pMD18-T载体上,转化至BL21感受态细胞中;重组质粒经PCR及酶切鉴定后,送上海生工测序。将鉴定正确的质粒酶切回收产物与原核表达载体pET-32a连接,然后转化至BL21感受态细胞,对平板筛选的阳性质粒进行PCR和酶切鉴定。对鉴定正确的重组菌进行诱导表达并纯化。实验结果表明成功构建了pET32a-eno表达载体,并获得了该纯化蛋白。该实验结果为S.aureus亚单位疫苗研究奠定了一定的基础。 相似文献
17.
出血性大肠杆菌O157：H7的Tir与stx1／2B融合基因的构建和表达 总被引：4，自引：0，他引：4
为了更好防治由出血性大肠杆菌O157：H7引起的疾病,尝试研制基因工程疫苗．其中亚单位疫苗具有很大优势。方法：构建表达tir和stxb的融合基因。将tir基因中间295个氨基酸残基（Tir295）与stxB亚基基因72个氨基酸串联。构建pET28a—stx2b—Tir295-stx1b重组质粒,将其转化于BL21（DE3）,用IPTG进行诱导表达,经SDS--PAGE电沫检测,该融合蛋白获得了高效表达。结果：薄层扫描分析表明,目的蛋白表达量占菌体总蛋白含量的30％左右。结论：由于该融合蛋白由Tir、stx1b和stx2b三部分抗原组成．可刺激机体产生针时转位紧密素受体（Tir）和志贺毒素（stx）的抗体,在EHEC0157亚单位疫苗设计或单克隆抗体抗制备中具有重要价值。 相似文献
18.
New method for detecting cellular transforming genes 总被引：24，自引：0，他引：24
D G Blair C S Cooper M K Oskarsson L A Eader G F Vande Woude 《Science (New York, N.Y.)》1982,218(4577):1122-1125
Tumor induction in athymic nude mice can be used to detect dominant transforming genes in cellular DNA. Mouse NIH 3T3 cells freshly transfected with either cloned Moloney sarcoma proviral DNA or cellular DNA's derived from virally transformed cells induced tumors when injected into athymic nu/nu mice. Tumors were also induced by cells transfected with DNA from two tumor-derived and one chemically transformed human cell lines. The mouse tumors induced by human cell line DNA's contained human DNA sequences, and DNA derived from these tumors was capable of inducing both tumors and foci on subsequent transfection. Tumor induction in nude mice represents a useful new method for the detection and selection of cells transformed by cellular oncogenes. 相似文献
19.
A cytosolic protein catalyzes the release of GDP from p21ras 总被引：35，自引：0，他引：35
The rate of release of guanine nucleotides from the ras proteins (Ras) is extremely slow in the presence of Mg2+. It seemed likely, therefore that a factor might exist to accelerate the release of guanosine diphosphate (GDP), and hence the exchange of GDP for guanosine triphosphate (GTP). Such a factor has now been discovered in rat brain cytosol. Brain cytosol was found to catalyze, by orders of magnitude, the release of guanine nucleotides from recombinant v-H-Ras protein bound with [alpha-32P]GDP. This effect occurred even in the presence of a large excess of Mg2+, but was destroyed by heat or by incubation of the cytosol for an hour at 37 degrees C in the absence of phosphatase inhibitors. The effect was observed with either v-H-Ras or c-H-Ras, but not with p25rab3A, a small G protein with about 30% similarity to Ras. The effect could not be mimicked by addition of recombinant Ras-GAP or purified GEF, a guanine nucleotide exchange factor involved in the regulation of eukaryotic protein synthesis. By gel filtration chromatography, the factor appears to possess a molecular size between 100,000 and 160,000 daltons. This protein (Ras-guanine nucleotide-releasing factor, or Ras-GRF) may be involved in the activation of p21ras. 相似文献
20.
Endoreduplication is an endonuclear chromosome duplication that occurs in the absence of mitosis and in Zea mays (L.) is required for endosperm development. Induction of DNA synthesis during early stages of endosperm development is maintained by increasing the amount and activity of S phase-related protein kinases, which was demonstrated here by their ability to interact with human E2F or with the adenovirus E1A proteins. In addition it was shown that endoreduplicated endosperm cells contain an inhibitor that suppresses the activity of the M phase-promoting factor (MPF). These results demonstrate that in maize endosperm, endoreduplication proceeds as a result of two events, inhibition of MPF and induction of S phase-related protein kinases. 相似文献