视网膜母细胞瘤基因产物磷酸化水平与细胞生长状态的关系

随着无血清培养细胞时间的延长，红胞合成Ｒｂ蛋白量和磷酸化水平逐渐降低，当细胞生长停止时，Ｒｂ蛋白处于低磷外化状态．正丁酸钠可诱导ＨＬ６０终端分化为单核－巨噬细胞；视黄酸、二甲基亚砜使ＨＬ６０分化为粒细胞．尽管分化途径不同．但是终端分化的细胞都只能合成低磷酸化的Ｒｂ蛋白．结果表明当细胞处于生长停滞状态，细胞都只能合成低磷酸化的Ｒｂ蛋白．     

血清浓度对SMMC—7721细胞DNA合成的影响

以人肝癌ＳＭＭＣ－７７２１细胞为材料研究了不同血清浓度对ＤＮＡ合成和细胞生长状态的影响，结果表明几乎在所有处理中短时无血清培养都能刺激ＳＭＭＣ－７７２１细胞的ＤＮＡ合成，且＾３Ｈ－ＴｄＲ掺入量与培养液中ＦＣＳ浓度成明显负相关，＾３Ｈ－ＴｄＲ掺入量比值最高可达３９．３２倍．１８ｈ内，随培养时间的增加无血清培养对细胞ＤＮＡ合成的刺激作用逐渐下降，＾３Ｈ－ＴｄＲ掺入量比值从３９．３２倍下降为３．５３倍，     

血清浓度对SMMC－7721细胞DNA合成的影响

以人肝癌ＳＭＭＣ—７７２１细胞为材料研究了不同血清浓度对ＤＮＡ合成和细胞生长状态的影响，结果表明几乎在所有处理中短时无血清培养都能刺激ＳＭＭＣ—７７２１细胞的ＤＮＡ合成，且３Ｈ—ＴｄＲ掺入量与培养液中ＦＣＳ浓度成明显负相关，３Ｈ—ＴｄＲ掺入量比值最高可达３９．３２倍．１８ｈ内，随培养时间的增加无血清培养对细胞ＤＮＡ合成的刺激作用逐渐下降，３Ｈ—ＴｄＲ掺入量比值从３９．３２倍下降为３．５３倍，结果提示人肝癌ＳＭＭＣ—７７２１细胞对培养液中短时无血清的反应不同于其它细胞株     

α-亚麻酸对胰岛素抵抗HepG2细胞脂类合成基因表达的影响

目的分析在α-亚麻酸(ALA,C18:3)干预后,胰岛素抵抗Hep G2(insulin resistance Hep G2,IR-Hep G2)细胞模型脂类合成关键基因表达水平的变化。方法 Hep G2细胞造模期分为两组,由无血清培养基培养的对照组(normal control group,NC)以及含有0.25 mmol/L软脂酸的无血清培养基培养的软脂酸组(palmitic acid,PA),培养24 h后鉴定细胞胰岛素敏感性并测定细胞内胆固醇(total cholesterol,TCH)、甘油三酯(Tryglyceride,TG)水平,然后用ALA替代20%的PA培养12 h,再次鉴定细胞胰岛素敏感性并检测细胞内TCH、TG水平,real time q PCR检测TG、TCH合成关键基因mRNA水平,Western blot检测TG、TCH合成关键基因蛋白表达量。结果 IR-Hep G2细胞模型建立成功,并且PA组TCH水平显著高于NC组(P=0.0016),出现了脂代谢紊乱;ALA干预IR-Hep G2细胞12 h后,细胞活性有所恢复,与PA组相比,ALA组胰岛素诱导基因(insulin induced genes,INSIGs)及脂类合成关键蛋白的mRNA表达无明显变化;与基因表达结果不一致的是,ALA干预后可以特异性提升细胞内INSIG-2蛋白相对表达量,但对INSIG-1蛋白相对表达量没有明显影响。同时,ALA可以显著抑制55k Da固醇调节元件结合蛋白-2(sterol regulatory element-binding protein-2,SREBP-2)、HMG-Co A还原酶(3-hydroxy-3-methyl glutaryl coen-zyme A reductase,HMGCR)及脂肪酸合酶(fatty acid synthase,FASN)蛋白的表达,且ALA组细胞内TG水平显著降低(P=0.0119)。结论 0.05 mmol/L ALA干预IR-Hep G2细胞后,通过提升INSIG-2蛋白的表达,抑制SREBP-2从内质网到高尔基体的剪切成熟活化,降低细胞内55k Da SREBP-2水平及HMGCR的表达,并且抑制FASN表达,从而抑制了TG/TCH的合成。     

细胞外基质对体外培养兔关节软骨细胞增殖及基质代谢的影响

目的：观察软骨组织的主要细胞外基质成分：Ⅱ型胶原、蛋白多糖、透明质酸对体外单层培养的兔关节软骨细胞的增殖及基质合成的影响。方法：原代分离、培养兔关节软骨细胞，分别向其中添加Ⅱ型胶原、蛋白多糖和透明质酸。采用改良MTT法检测细胞的增殖情况，Aleian Blue法检测基质蛋白多糖含量及羟脯氨酸法测定软骨细胞胶原产量。结果：单独添加Ⅱ型胶原（50μg／mL）组、蛋白多糖（50μg／mL）组和透明质酸（100μg／mL）组及三者联合添加实验组与对照组相比，对关节软骨细胞的增殖及胶原、蛋白多糖的合成未见明显统计学差异（P〉0．05）。结论：正常软骨组织的主要基质成分对体外培养的兔关节软骨细胞增殖、蛋白多糖和胶原的合成无明显影响。     

不同癌细胞系中gp96的唾液酸化程度研究

以自行合成的叠氮标记的甘露糖进行细胞代谢,代谢后以叠氮化的唾液酸替代天然的唾液酸于细胞糖蛋白的糖链中呈现,依赖于点击化学方法,建立分离唾液酸化糖蛋白的方法,并研究gp96蛋白在不同癌细胞系中的唾液酸化程度.经酶联免疫吸附反应检测各细胞系均含有gp96蛋白,且含量无显著差异.而分析gp96的生物素化和唾液酸修饰程度,发现...     

小鼠细小病毒VP2蛋白在昆虫细胞-杆状病毒系统中的表达和免疫原性分析

目的 利用杆状病毒表达系统合成重组小鼠细小病毒(MVM)VP2蛋白，并对其免疫原性分析。方法 将优化后的MVM VP2序列克隆至表达载体pFastBac1,命名为pFastBac1-MVM VP2,再将其转化至DH10Bac感受态大肠杆菌中形成重组杆粒，提取重组杆粒经PCR鉴定正确后转染昆虫细胞Sf9,镜下观察到细胞明显病变后收获重组杆状病毒rBac-MVM VP2。Sf9细胞接重组病毒48和72 h后，用间接免疫荧光(IFA)和蛋白免疫印迹(Western blot)法验证重组蛋白的免疫原性。结果 构建的rBac-MVM VP2重组杆状病毒感染Sf9细胞后，可成功表达MVM VP2重组蛋白，经Western blot和IFA检测分析，重组蛋白具有较好的免疫原性且在病毒感染72 h时表达量较高。经蛋白纯化后可得到纯度较高的VP2重组蛋白。结论 本研究利用昆虫细胞-杆状病毒系统成功表达MVM VP2蛋白并具有良好的免疫原性，为VP2相关功能的研究和临床诊断方法的建立奠定基础。     

沙棘提取物对癌细胞DNA,蛋白质合成及体内血浆中cAMP…

采用同位素示踪技术和蛋白质结合研究了沙棘汁和沙棘油的抗癌机理。结果显示：沙棘汁对Ｌ７７１２白血病、Ｓ１８０肉瘤、腹水型肝癌等细胞的ＤＮＡ、蛋白质合成均无抑作用。沙棘油浓度在０．００５～１．０ｍｇ／Ｌ时对Ｌ７７１２白血病细胞ＤＮＡ合成的抑制作用，且此进抑制率与浓度呈负相关。沙棘汁ｉｐ注射剂量为１／５ＬＤ５０时，沙棘汁对小鼠血浆ｃＡＭＰ含量略有提高。     

沙棘提取物对癌细胞DNA、蛋白质合成及体内血浆中cAMP含量的影响

采用同位素示踪技术和蛋白质结合法研究了沙棘汁和沙棘油的抗癌机理。结果显示：沙棘汁对Ｌ＿（７７１２）白血病、Ｓ＿（１８０）肉瘤、腹水型肝癌等细胞的ＤＮＡ、蛋白质合成均无抑制作用。沙棘油浓度在０．００５～１．０ｍｇ／Ｌ时对Ｌ＿（７７１２）白血病细胞ＤＮＡ合成有抑制作用，且此时抑制率与浓度呈负相关。沙棘汁ｉｐ注射剂量为１／５ＬＤ＿（５０）时，沙棘汁对小鼠血浆ｃＡＭＰ含量略有提高。     

Bcl—2基因加强表达对OA诱发的细胞编程死亡的效应

ＯＡ能诱发人神经母细胞瘤ＳＫ细胞编程互亡，死亡细胞缩小为圆，细胞质凝聚，ＤＮＡ有控降解成约２００ｂｐ左右的片段，且这一过程可由蛋白南合成抑制剂环己酮抑制将编码Ｂｃｌ－２全长蛋白质的ｃＤＮＡ植入ｐＸＪ４ｌｎｅｏ载体中，使其表达由ＨＣＭＶ病毒启动子控制。     

Inhibition of mitosis by an antibody to the mitotic calcium transport system

Calcium ions are important in the regulation of mitotic apparatus assembly and in the control of chromosome movement. Changes in intracellular free calcium concentration, [Ca2+]i are achieved by an intracellular calcium-transport system which is highly conserved in different cell types. A membrane-bound protein of relative molecular mass (Mr) 46,000 (46K) is part of this transport system and has been implicated in the regulation of the [Ca2+]i changes associated with the course of mitosis. A monoclonal antibody against this 46K protein inhibits Ca2+-uptake into isolated Ca2+-sequestering membranes and specifically labels membranes associated with the mitotic apparatus of sea urchin embryos. Here we investigate the relationship between the intracellular calcium transport system and mitosis by injection of this monoclonal antibody into living mitotic sea urchin embryos. We find that after injection the intracellular free calcium increases up to 10(-6) M, the mitotic apparatus is rapidly destroyed and the cell is irreversibly blocked in its development.     

Translational control of InsP3-induced chromatin condensation during the early cell cycles of sea urchin embryos

The cycles of DNA synthesis and chromatin condensation in dividing cells are controlled by signals from the cytoplasm. Changes in the concentration of free calcium (Cai) in the cytoplasm control a variety of cellular functions and it has thus been suggested that observed variations in Cai during the cell cycle may be the cytoplasmic signal that co-ordinates nuclear and cytoplasmic division. We show here that increases in Cai induced by the calcium-releasing second messenger inositol 1,4,5-triphosphate (Ins(1,4,5)P3), or by calcium buffers, cause premature chromatin condensation and breakdown of the nuclear envelope in sea urchin (Lytechinus pictus) early embryos. Both natural and induced chromatin condensation are prevented by calcium chelators. The nucleus becomes sensitive to the Cai signal 45 min after fertilization, but remains insensitive if protein synthesis is prevented. Our experiments demonstrate that Cai regulates the behaviour of the nucleus during the cell cycle, suggest that Ins(1,4,5)P3 is a cell cycle messenger and indicate that there is an interaction between the protein and ionic signals that control the state of chromatin during the cell cycle.     

A keratin cytoskeletal protein regulates protein synthesis and epithelial cell growth

Cell growth, an increase in mass and size, is a highly regulated cellular event. The Akt/mTOR (mammalian target of rapamycin) signalling pathway has a central role in the control of protein synthesis and thus the growth of cells, tissues and organisms. A striking example of a physiological context requiring rapid cell growth is tissue repair in response to injury. Here we show that keratin 17, an intermediate filament protein rapidly induced in wounded stratified epithelia, regulates cell growth through binding to the adaptor protein 14-3-3sigma. Mouse skin keratinocytes lacking keratin 17 (ref. 4) show depressed protein translation and are of smaller size, correlating with decreased Akt/mTOR signalling activity. Other signalling kinases have normal activity, pointing to the specificity of this defect. Two amino acid residues located in the amino-terminal head domain of keratin 17 are required for the serum-dependent relocalization of 14-3-3sigma from the nucleus to the cytoplasm, and for the concomitant stimulation of mTOR activity and cell growth. These findings reveal a new and unexpected role for the intermediate filament cytoskeleton in influencing cell growth and size by regulating protein synthesis.     

Three-dimensional structure of the free radical protein of ribonucleotide reductase

The enzyme ribonucleotide reductase furnishes precursors for the DNA synthesis of all living cells. One of its constituents, the free radical protein, has an unusual alpha-helical structure. There are two iron centres that are about 25 A apart in the dimeric molecule. Tyrosine 122, which harbours the stable free radical necessary for the activity of ribonucleotide reductase, is buried inside the protein and is located 5 A from the closest iron atom.     

Cyclin/PCNA is the auxiliary protein of DNA polymerase-delta

Identification of the cellular proteins whose expression is regulated during the cell cycle in normal cells is essential for understanding the mechanisms involved in the control of cell proliferation. A nuclear protein called cyclin of relative molecular mass 36,000 (Mr 36K), whose synthesis correlates with the proliferative state of the cell, has been identified in several cell types of human, mouse, hamster and avian origin. The rate of cyclin synthesis is very low in quiescent cells and increases several fold after serum stimulation shortly before DNA synthesis. Immunofluorescence and autoradiography studies have shown that the nuclear staining patterns of cyclin during S phase have a sequential order of appearance and a clear correlation can be found between DNA synthesis and cyclin positive nuclei. The proliferating cell nuclear antigen (PCNA) and cyclin have many common properties and it has been shown that these two are identical. Recently a protein which is required by DNA polymerase-delta for its catalytic activity with templates having low primer/template ratios has been isolated from calf thymus. We report here that cyclin and the auxiliary protein of DNA polymerase-delta are identical.     

Selective localization of messenger RNA for cytoskeletal protein MAP2 in dendrites

For nerve cells to develop their highly polarized form, appropriate structural molecules must be targeted to either axons or dendrites. This could be achieved by the synthesis of structural proteins in the cell body and their sorting to either axons or dendrites by specific transport mechanisms. For dendrites, an alternative possibility is that proteins could be synthesized locally in the dendritic cytoplasm. This is an attractive idea because it would allow regulation of the production of structural molecules in response to local demand during dendritic development. The feasibility of dendritic protein synthesis is suggested both by the existence of dendritic polyribosomes and by the recent demonstration that newly synthesized RNA is transported into the dendrites of neurons differentiating in culture. However, to date there has been no demonstration of the selective synthesis of an identified dendrite-specific protein in the dendritic cytoplasm. Here, we use in situ hybridization with specific complementary DNA probes to show that messenger RNA for the dendrite-specific microtubule-associated protein MAP2 (refs 3-5) is present in dendrites in the developing brain. By contrast the mRNA for tubulin, a protein present in both axons and dendrites is located exclusively in neuronal cell bodies.     

Membrane leakiness after viral infection and a new approach to the development of antiviral agents.

Viral development induces changes in the permeability properties of the plasma membrane of the host cell. Here it is shown that, because of this leakiness, inhibitors of protein synthesis normally impermeable to uninfected cells are able to enter infected cells and thereby specifically inhibit viral protein synthesis.     

Negative regulation of transforming growth factor-beta by the proteoglycan decorin

Decorin is a small chondroitin-dermatan sulphate proteoglycan consisting of a core protein and a single glycosaminoglycan chain. Eighty per cent of the core protein consists of 10 repeats of a leucin-rich sequence of 24 amino acids. Similar repeats have been found in two other proteoglycans, biglycan and fibromodulin, and in several other proteins including Drosophila morphogenetic proteins. Expression of high levels of decorin in Chinese hamster ovary cells has a dramatic effect on their morphology and growth properties. We now report that this effect is due at least in part to the ability of decorin to bind transforming growth factor-beta, an autocrine factor that stimulates the growth of Chinese hamster ovary cells. As transforming growth factor-beta induces synthesis of decorin in many cell types, our results suggest that decorin may be a component of a feedback system regulating cell growth.     

Protein synthesis required to anchor a mutant p53 protein which is temperature-sensitive for nuclear transport

The p53 protein is rendered temperature-sensitive by a point mutation. Rat cells transformed by this mutant p53 and an activated ras oncogene grow well at 37 degrees C but cease DNA synthesis and cell division when shifted to 32 degrees C. Immunostaining demonstrates that the mutant p53 protein is in the nucleus of the arrested cells at 32 degrees C but in the cytoplasm of the growing cells at 37 degrees C. This is the first example of a protein which is temperature-sensitive for nuclear transport. The translocation from cytoplasm to nucleus and vice versa occurs 6 h after temperature shift and is coincident with the inhibition of DNA synthesis; transport from cytoplasm to nucleus does not require protein synthesis. Remarkably, inhibition of protein synthesis at 37 degrees C also results in the rapid appearance of mutant p53 in the cell nucleus. These results suggest the presence of a short-lived protein responsible for holding p53 in the cytoplasm at 37 degrees C but not at 32 degrees C. Analysis of a non-temperature-sensitive mutant p53 protein shows that its cytoplasmic location is sensitive to protein synthesis inhibitors but not to temperature.     

Immunoglobulin heavy chain binding protein

Pre-B lymphocytes, and hybridomas derived from them, synthesize immunoglobulin heavy (IgH) chain in the absence of light (L) chain. In the Abelson virus transformed line 18-81, which is representative of the pre-B cell stage, we observed that at least some of the H-chains are bound to a protein other than L-chain. Here we show that the protein (which we term immunoglobulin heavy-chain binding protein, BiP) binds non-covalently to free IgH, but not to IgH associated with IgL.