衰老过程中鼠肝细胞核体外重组的转录活性

本文以０．３５ｍｏｌ／Ｌ ＫＣｌ抽提不同年龄鼠肝细胞,将抽提后细胞核分别与抽提物、纯化的染色质高迁移率非组蛋白（ＨＭＧ）及组蛋白Ｈ１进行重组。结果表现,０．３５ｍｏｌ／Ｌ ＫＣｌ抽提后老年鼠肝细胞与断乳鼠肝细胞核抽提物重组转录活性高于其与自身或青年鼠肝细胞核抽提液重组者。还发现高迁移率非组蛋白可提高抽提后鼠肝细胞核转录活性,对断乳鼠的作用最强;但不影响未经抽提的细胞核转录活性。相反,组蛋白Ｈ１则可     

牛微量白细胞样品的处理及其Y染色体特异DNA的扩增

本文建立了牛微量白细胞样品的处理及其Ｙ染色体特异ＤＮＡ的扩增的方法。采集成年公牛全血,用ＥＤＴＡ抗凝血。分离白细胞,用０．１４５ｍｏｌ／ＬＮａＣｌ洗净,用０．１４５ｍｏｌ／ＬＮａＣｌ稀释,计数。分别将０．５、５０、５００细胞在含１０ｍｍｏｌ／ＬＴｒｉｓ－ＨＣｌ、５０ｍｍｏｌ／ＬＫＣｌ、２ｍｍｏｌ／ＬＭｇＣｌ２、０．４５％ＮＰ－４０、０．４５％Ｔｗｅｅｎ－２０、０．１ｍｇ／ｍＬ蛋白酶Ｋ、总体积２０μ     

应用抗体探针对人食管癌组织，Eca－109细胞及其染色体的NHP免疫反应性研究

应用自制的癌非组蛋白（ＮＨＰ）抗体探针,探讨了人食管癌Ｅｃａ－１０９细胞及其染色体和人食管癌组织的ＮＨＰ免疫反应性。结果表明：①以０．４ｍｏｌ／Ｌ及０．３５ｍｏｌ／ＬＮａＣｌ提取的ＮＨＰ均含１．１４万－４万道尔顿分子量的高速泳动族蛋白（Ｈｉｇｈｍｏｂｉｌｉｔｙｇｒｏｕｐｐｒｏｔｅｉｎ,ＨＭＧＰ）。②在人食管癌切片标本上癌细胞核、胞质、胞核均呈免疫反应阳性,且胞膜、胞质反应强于胞核。并见到癌巢周缘细胞比癌巢中心的细胞反应较强。③人食管瘤Ｅｃａ－１０９细胞的胞膜、胞质、胞核均呈ＮＨＰ免疫反应阳性,多见胞膜、胞质强于胞核。④人食管癌Ｅｃａ－１０９细胞的分裂中期染色体上,免疫反应呈阳性。这提示０．４ｍｏｌ／ＬＮａＣｌ提取的ＮＨＰ含有ＤＮＡ特异结合的ＮＨＰ组分。     

NaCl（2 mol／L）处理PSⅡ颗粒的Ca^2＋重结合

回加Ｃａ＾２＋对ＮａＣｌ（２ ｍｏｌ／Ｌ）处理菠菜ＰＳⅡ颗粒放氧活恬的作用表现出有两种Ｋｍ值分别为０．０２１和０．５４５ｍｍｏｌ／Ｌ高亲和与低亲和的Ｃａ＾２＋重结合过程。高浓度ＮａＣｌ和低ｐＨ（３．０）处理支Ｃａ的ＰＳⅡ颗粒的光抑制放氧活性半衰期明显减小,重结合Ｃａ＾２＋后,虽然大部分丧失的放氧活性可恢复,但ＰＳⅡ颗粒放氧活性对光抑制的敏感性却并不随之恢复,ｔ１／２无明显改变。显然,重组Ｃａ＾２＋     

核受体辅助因子及其信号转导

类固醇激素、核受体及其辅助因子在细胞增殖、分化中起重要的作用。核受体与相应的配体结合后同细胞内的辅助激活因子ＣＢＰ／Ｐ３００、ＰＣＡＦ、Ｐ／ＣＩＰ和ＳＲＣ家族等结合形成的复合物能使组蛋白乙酰化促进基因的转录,当缺乏配体时核受体同辅助抑制因子ＳＭＲＩ、mSin3A及ＨＡＤ１具有很强的结合力使组蛋白去乙酰化抑制基因的转录活性。ＭＡＰＫ、ＰＫＡ、ＡＰ－１、Ｓap-a、ＪＡＫ／ＳＴＡＴ、ＪＡＫ信号传导中核受体辅助因子参与信号传导过程影响基础的转录。     

铝对玉米生长和硝酸还原酶活性的影响

测定了生长在Ａｌ２（ＳＯ４）３１００μｍｏｌ／Ｌ氮素营养液中的两个玉米品种（ＳＣ７０４和ＶＡ３５的根系和叶片）的ＮＡＤＨ－硝酸还原酶（ＥＣ１．６．６．１）和ＮＡＤ（Ｐ）Ｈ－硝酸还原酶（ＥＣ１．６．６．２）活性。     

蚯蚓体内一种纤溶酶原激活剂(e-PA)对ATEE的降解

赤子爱胜蚓（Ｅｉｓｅｎｉａｆｅｔｉｄａ）体内的一种纤溶酶原激活剂（ｅ－ＰＡ）能够降解人工合成底物Ｎ－乙酰－Ｌ－酪氨酸乙酯（ＡＴＥＥ）,该降解反应的最适ｐＨ为８．５,而且在０．２ｍｏｌ／ＬＮａ２ＨＰＯ４中的活性要强于在０．０５ｍｏｌ／ＬＴｒｉｓ－ＨＣｌ（ｐＨ８．５）中．分别测定了ｅ－ＰＡ的大小亚基及全酶在０．２ｍｏｌ／ＬＮａ２ＨＰＯ４与０．０５ｍｏｌ／ＬＴｒｉｓ－ＨＣｌ（ｐＨ８．５）两种体系中的Ｋｍ和Ｋｃａｔ．结果表明,在０．２ｍｏｌ／ＬＮａ２ＨＰＯ４中,全酶的ＡＴＥＥ活性远远高于大小亚基单独的ＡＴＥＥ活性,而在０．０５ｍｏｌ／ＬＴｒｉｓ－ＨＣｌ（ｐＨ８．５）中则没有这种现象．从蛋白质结构的角度对这一结果作了解释．用不同抑制剂和ｅ－ＰＡ作用,结果表明,ｐｅｐｓｔａｔｉｎ,Ｅ－６４和ＥＤＴＡ对ｅ－ＰＡ的ＡＴＥＥ活性都有不同程度的抑制,这一点与ｅ－ＰＡ的ＢＡＥＥ活性不同．     

大鼠前列腺甾体结合蛋白C3基因CAAT区核内结合蛋白…

为了解结合在大鼠前列腺甾体蛋白Ｃ３基因ＣＡＡＴ区的核区结合蛋白在此基因表达活跃的前列腺中和不表达的肝脏中的异同;我们用肝素琼脂糖柱层析将两种组织的核抽提液分别进行分级分离,用ＤＮａｓｅＩ足迹法和凝胶阻滞法分析表明：（１）所有ＣＡＡＴ区结合蛋白被富集在０．２－０．５ｍｏｌ／Ｌ ＮａＣｌ洗脱液中;（２）在凝胶阻滞谱上的各种蛋白组分能按迁移率的大小分布在不同浓度的ＮａＣｌ洗脱液中;（３）竞争分析表明：在     

LHRH—A2及无机离子促进草鱼脑垂体离体分泌GH的初步研究

用培养瓶（皿）培养法研究ＬＨＲＨ－Ａ２、Ｃａ＾２＋、Ｋ＾＋对草鱼脑垂体器官分泌ＧＨ的影响。结果表明，１ｎｍｏｌ／Ｌ、１０ｎｍｏｌ／Ｌ、１００ｎｍｏｌ／Ｌ和１０００ｎｍｏｌ／Ｌ的ＬＨＲＨ－Ａ２都能显著促进ＧＨ的分泌；随着Ｃａ＾２＋浓度（０．１、１、３ｍｍｏｌ／Ｌ）的增高ＧＨ的分泌增强，在１ｍｏｌ／Ｌ和３ｍｍｏｌ／Ｌ Ｃａ＾２＋条件下的ＧＨ分泌水平显著高于在０．１ｍｍｏｌ／Ｌ Ｃａ＾２＋条件下的ＧＨ分     

肝细胞生长因子对四氯化碳损伤肝细胞的保护作用及相关基因表达

利用无血清原代培养大鼠肝细胞,观察重组人肝细胞生长因子（ｒｈＨＧＦ）对ＣＣｌ４染毒肝细胞的保护作用。结果表明：（１）ｒｈＨＧＦ（５ｎｇ／ｍｌ）预自理后可显著提高ＣＣｌ４（１５ｍｍｏｌ／Ｌ）染毒肝细胞存活率,降低细胞内丙氨酸氨基转移酶（ＡＬＴ）、Ｋ＾＋的漏出;（２）表皮生长因子（ＥＧＦ,５０ｎｇ／ｍｌ）和ｒｈＨＧＦ（５ｎｇ／ｍｌ）合用预处理肝细胞,ＣＣｌ４染毒后细胞内ＡＬＴ、Ｋ＾＋漏出较ｒｈＨＧＦ和     

High Mobility Group 1 Protein Is Not Stably Associated with the Chromosomes of Somatic Cells

High mobility group 1 (HMG1) protein is an abundant and conserved component of vertebrate nuclei and has been proposed to play a structural role in chromatin organization, possibly similar to that of histone H1. However, a high abundance of HMG1 had also been reported in the cytoplasm and on the surface of mammalian cells. We conclusively show that HMG1 is a nuclear protein, since several different anti-HMG1 antibodies stain the nucleoplasm of cultured cells, and epitope-tagged HMG1 is localized in the nucleus only. The protein is excluded from nucleoli and is not associated to specific nuclear structures but rather appears to be uniformly distributed. HMG1 can bind in vitro to reconstituted core nucleosomes but is not stably associated to chromatin in live cells. At metaphase, HMG1 is detached from condensed chromosomes, contrary to histone H1. During interphase, HMG1 readily diffuses out of nuclei after permeabilization of the nuclear membranes with detergents, whereas histone H1 remains associated to chromatin. These properties exclude a shared function for HMG1 and H1 in differentiated cells, in spite of their similar biochemical properties. HMG1 may be stably associated only to a very minor population of nucleosomes or may interact transiently with nucleosomes during dynamic processes of chromatin remodeling.     

Regulation of DNA primase activity by phosphorylation of histone-H1 in regenerating rat liver

The biological importance of histone H1 was investigated in relation to the cell cycle using liver regeneration in rat. Histone H1 was extracted from the regenerating rat liver at various intervals after partial hepatectomy and the number of phosphate residues was measured. The inhibitory effect of the extracted histone H1 on DNA primase was assayed. The activities of DNA polymerase-alpha, DNA primase and DNA synthesis were also determined in the regenerating rat liver. It was found that: 1) phosphate residue in histone H1 from normal rat liver was between 2-3 mol/mol of histone H1. 2) The number of phosphate residues did not change for the first 16h after partial hepatectomy. 3) A dramatic sudden increase of phosphate residues was detected at 18h after partial hepatectomy. 4) The high levels of phosphate residues remained constant thereafter up to 50h. 5) DNA primase activity was less inhibited by highly phosphorylated than by slightly phosphorylated histone H1. It seems probable that phosphorylation of histone H1 is needed for the releasing of DNA primase activity from its inhibited state, which would start DNA synthesis together with DNA polymerase-alpha.     

Histone H1 binding at the 5' end of the rat albumin gene

Cloned DNA containing the first nine exons of the rat albumin gene was digested with EcoRI and HindIII, and the resulting fragments were used to screen for regions with relatively high affinity for protein. Of three restriction fragments preferentially bound, the fragment containing the first two exons of the albumin gene was consistently bound over others by heat-stable protein extracted from liver nuclei with 0.35-1.0 M NaCl. Proteins extracted with lower and higher ionic strength buffers bound the DNA fragments, but with little specificity. The DNA fragment that was preferentially bound consistently by the 1.0 M nuclear extract was subcloned into pBR325 and was used to isolate the specific DNA-binding activity. After purification, histone H1 was the polypeptide with preferential DNA-binding activity. Histone H1 has a high-affinity binding site in the 5' end of the rat albumin gene within 440 5'-flanking base pairs and the first two exons of the gene.     

Metabolism of histones and non-histone proteins in liver cell nuclei and chromatin from rats of various ages

The metabolism of various classes of histones and nonhistone proteins in intact nuclei and in liver chromatin of albino Wistar rats aged 1, 3, 12 and 24 months, was studied. It was shown that in the course of postnatal development the metabolism of nonhistone proteins extracted with 0.14 M NaCl in murine liver is increased. Later in ontogenesis, the incorporation of labeled precursors into proteins HMG 14 and HMG 17 decreases; the specific radioactivity of proteins HMG 1 + 2 is higher in 3- and 24-month-old animals. The intensity of metabolism of nonhistone proteins and histones is higher within the composition of the chromatin complex than in the intact nucleus at all stages of postnatal development. Among other histone proteins, histones H1 are characterized by the highest level specific radioactivity in rats of all age groups.     

Proteins from nuclear fractions with different contents of active genes

The protein content in four nuclear fractions was compared. The nuclear fraction of rat liver deficient in active genes was characterized by a very low content of non-histone proteins whose mobility is less than that of histone H1.. The predominant protein of this fraction is an acid-soluble protein (Mr = 41 +/- 1 kD) designated as 41K. This protein was detected in acid nuclear extracts of rat lungs, kidney and spleen but was absent (or practically absent) in four murine and rat hepatomas under study. The decreased content of protein 41K was correlated with the diminution of the content of histone H1(0) fraction. It was shown that proteins HMG 14 and 17 are readily washed off during fractionation of nuclei and they bind to DNA fragments passing into solution irrespective of whether they contain active or inactive genes. The nuclear matrix fraction rich in active genes was heterogeneous according to its protein composition. Differences in the intensity of staining and in electrophoretic mobility of some polypeptides of this nuclear fraction in normal and hepatoma cells were revealed.     

High mobility group proteins in ram spermatids

The four major high mobility group proteins HMG 1, 2, 14 and 17, HMG 19B and histone H1(0) were identified in the ram testis by their extraction and solubility characteristics and by their electrophoretic mobilities. HMG 14 and 17 were isolated by chromatography and amino acid analysis revealed that they were similar to their calf thymus analogues. A protein, named 2R and co-extracted with HMG 14, was also purified and analysed. Electrophoretic analyses of the proteins extracted by 0.75 M perchloric acid (PCA) or by 0.35 M NaCl from round and non-round spermatids, separated by centrifugal elutriation, showed that the four major HMG proteins disappear from nuclei in the oldest round spermatids, at the time the nuclear content of protein 2R and histone H1(0) increases in spermatids. Ubiquitin and HMG 19B were present in the round and elongating spermatids, but not in elongated spermatids which contained only protamine. The relation was considered between several protein changes and genetic inactivation and structural reorganization of the spermatid chromatin.     

Tetrahymena HMG nonhistone chromosomal protein. Isolation and amino acid sequence lacking the N- and C-terminal domains of vertebrate HMG 1

The complete amino acid sequence of a high mobility group (HMG) nonhistone chromosomal protein of the ciliated protozoan Tetrahymena pyriformis (GL strain) was determined. This protein was extracted with 0.5 M HClO4 together with histone H1 (molar ratio 1:1) from the whole histone extract, then purified by gel filtration and reverse-phase HPLC. The HMG protein showed a single electrophoretic band on SDS gel electrophoresis. The amino acid sequence was determined by Edman degradation of intact protein, BrCN fragments, and their staphylococcal protease and tryptic peptides. Thus the total sequence, consisting of 99 amino acid residues and having a molecular weight of 11,626, was completely determined. Phosphorus analysis of the tryptic peptides, containing serine or threonine, showed that this HMG protein was phosphorylated at two positions, each 6-7%, and contained 0.15 mol phosphate/mol protein. This Tetrahymena HMG is rather similar to the central part of vertebrate HMG 1 in terms of the amino acid sequence and the hydropathy profile.     

Rat liver HMG1: a physiological nucleosome assembly factor.

Incubation of rat liver single-stranded DNA-binding protein HMG1 with the four core histones at 0.15 M NaCl favors histone association primarily into tetramers and, to a lesser extent, into octamers. The assembly of pre-formed histone-HMG1 complexes with DNA yields nucleosome-like subunits which satisfy most of the criteria defining native core particles: (i) the circular DNA extracted from the complexes is supercoiled indicating that the initially relaxed DNA acquired superhelical turns during complex formation in the presence of topoisomerase I; (ii) the digestion of the complexes with micrococcal nuclease yields a DNA fragment of approximately 140 bp in length; (iii) electron microscopy of the reconstituted complexes shows a beaded structure with the DNA wrapped around the histone cores, leading to a reduction in the contour length of the genome compared with free DNA. Moreover, in the presence of HMG1, nucleosome assembly occurs rapidly at 0.15 M NaCl. Therefore, in addition to its DNA-binding properties, HMG1 mediates the assembly of nucleosomes in vitro under conditions of physiological ionic strength. The possible involvement of these properties in the DNA replication process is discussed.