Identification of a new gene in an operon for cellulose biosynthesis in Acetobacter xylinum

DNA sequencing of the region downstream of the cellulose synthase catalytic subunit gene of Acetobacter xylinum led to the identification of an open reading frame coding for a polypeptide of 86 kDa. The deduced amino acid sequence of this polypeptide matches from position 27 to 40 with the N-terminal amino acid sequence determined for a 93 kDa polypeptide that copurifies with the cellulose synthase catalytic subunit during purification of cellulose synthase. The cellulose synthase catalytic subunit gene and the gene encoding the 93 kDa polypeptide, along with other genes probably, are organized as an operon for cellulose biosynthesis in which the first gene is the catalytic subunit gene and the second gene codes for the 93 kDa polypeptide. The function of the 93 kDa polypeptide is not clear at present, however it appears to be tightly associated with the cellulose synthase catalytic subunit. Sequence analysis of the polypeptide shows that it is a membrane protein with a signal sequence at the N-terminal end and a transmembrane helix in the C-terminal region for anchoring it into the membrane.     

3α, 11α-Dihydroxy-23-oxo-lup-20(29)-en-28-oic acid from Acanthopanax trifoliatus

The new triterpene 3α,11α-dihydroxy-23-oxo-lup-20(29)-en-28-oic acid was isolated from Acanthopanax trifoliatus. Its structure has been determined on the basis of spectroscopic data and chemical transformations.     

中国人结肠癌nm23H1基因遗传不稳定性的研究

采用石蜡包埋组织抽提DNA、PCR-单链构象多态性(SSCP)、常规银染、Envision免疫组织化学和Leica-Qwin计算机图像分析等方法,研究中国人17号染色体D17S396位点微卫星不稳定性和杂合性缺失,对nm23H_1基因表达的影响,阐明nm23H_1基因遗传不稳定性与结肠癌进展的关系,为临床治疗提供实验依据。实验中,30例结肠癌D17S396位点MSI、LOH检出率和nm23H_1蛋白阳性率分别为26.67%、20.00%和53.33%。在肿瘤TNM分期中,Ⅰ+Ⅱ期的MSI检出率和nm23H_1蛋白阳性率分别为43.75%和81.25%,高于Ⅲ+Ⅳ期的7.14%(MSI,p<0.05)和21.43%(nm23H_1,p<0.01)。而LOH检出率在Ⅲ+Ⅳ期35.71%高于Ⅰ+Ⅱ期6.25%(p<0.05)。随着结肠癌病理Duke’s分期的升高,LOH检出率呈现增加趋势。nm23H_1蛋白阳性率在管状腺癌组为60.00%,明显高于粘液腺癌组的20.00%(p<0.01)。随着管状腺癌分化程度的升高,其阳性率呈增高趋势。此外,nm23H_1蛋白阳性率在MSI阳性组为75%,也高于MSI阴性组的45.45%(p<0.05)。计算机图像定量分析显示,nm23H_1蛋白在各临床病理参数影响下的表达强度没有差异。实验结果提示MSI和LOH通过相互独立的途径调控散发性结肠癌的进展。LOH多发生于散发性结肠癌的晚期阶段并赋予散发性结肠癌细胞高侵袭、低预后的表型。相反,MSI是散发性结肠癌的早期分子标志,提高结肠癌局部nm23H_1蛋白表达量可有效抑制结肠癌转移并改善散发性结肠癌患者预后。     

马铃薯X病毒湖南分离物的鉴定与分组研究

从湖南石门采集表现重花叶症状的马铃薯叶片中分离纯化到一株线状病毒HN021。经双链RNA(ds—RNA)抽提、寄主反应测定、病毒粒子和内含体的形状观察,初步确定该病毒为马铃薯X病毒(Potato virus X)。以ds—RNA作为模板,用相应引物对HN021分离物的ORF4-UTR-ORF5片段进行RT—PCRP得到1kb左右的双链cDNA片段。对该片段进行克隆和测序,并将测序所得的核苷酸序列与Genbank(登录的11株不同分离物的相应片段的核苷酸序列进行同源性比较和分析。结果表明,HN021与分离自南美洲的三株分离物(COAT,KPA和HB)的同源性为78．4％—79．4％,与其它8株(分离自亚洲、欧洲、大洋洲和北美洲)分离物的同源性为96．4％—97．8％。从氨基酸水平比较,HN021与COAT,KPA和HB三者CP和8kDa蛋白氨基酸序列同源性分别为86．5％—89．0％和74．3％—75．7％,相应地与其它8株分离物的同源性分别为97．1％—98．7％和97．1％—100％。序列分析的结果证实了HN021分离物为马铃薯X病毒,同时表明PVX明显存在两个组(组Ⅰ和组Ⅱ),HN021和其它来自亚洲、欧洲、大洋洲、北美洲分离物的组Ⅱ,3个南美洲分离物属于组Ⅰ。     

CD23McAb抑制活化B细胞增殖机制的初步探讨

本研究用ＣＤ２３单克隆抗体交联活化的人扁桃体Ｂ细胞,证明ＣＤ２３ＭｃＡｂ对Ｂ细胞呈双向调节效应,即：高浓度区抑制Ｂ细胞增殖,低浓度区促进Ｂ细胞增殖,继而,用对Ｂ细胞有抑制效应浓度的ＣＤ２３ＭｃＡｂ交联Ｂ细胞膜ＣＤ２３分子,通过研究抑制效应恢复条件,探讨了ＣＤ２３ＭｃＡｂ产生抑制效应的作用机制。结果显示：去除ＣＤ２３ＭｃＡｂ后,抑制作用不能恢复,用ＳＡＣ再次活化,使Ｂ细胞恢复增殖状态,用促Ｂ细胞增殖     

Phosphorylated and ubiquitinated TDP-43 pathological inclusions in ALS and FTLD-U are recapitulated in SH-SY5Y cells

We report phosphorylated and ubiquitinated aggregates of TAR DNA binding protein of 43 kDa (TDP-43) in SH-SY5Y cells similar to those in brains of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U). Two candidate sequences for the nuclear localization signal were examined. Deletion of residues 78-84 resulted in cytoplasmic localization of TDP-43, whereas the mutant lacking residues 187-192 localized in nuclei, forming unique dot-like structures. Proteasome inhibition caused these to assemble into phosphorylated and ubiquitinated TDP-43 aggregates. The deletion mutants lacked the exon skipping activity of cystic fibrosis transmembrane conductance regulator (CFTR) exon 9. Our results suggest that intracellular localization of TDP-43 and proteasomal function may be involved in inclusion formation and neurodegeneration in TDP-43 proteinopathies.     

Extracellular Nm23H1 stimulates neurite outgrowth from dorsal root ganglia neurons in vitro independently of nerve growth factor supplementation or its nucleoside diphosphate kinase activity

The nucleoside diphosphate (NDP) kinase, Nm23H1, is a highly expressed during neuronal development, whilst induced over-expression in neuronal cells results in increased neurite outgrowth. Extracellular Nm23H1 affects the survival, proliferation and differentiation of non-neuronal cells. Therefore, this study has examined whether extracellular Nm23H1 regulates nerve growth. We have immobilised recombinant Nm23H1 proteins to defined locations of culture plates, which were then seeded with explants of embryonic chick dorsal root ganglia (DRG) or dissociated adult rat DRG neurons. The substratum-bound extracellular Nm23H1 was stimulatory for neurite outgrowth from chick DRG explants in a concentration-dependent manner. On high concentrations of Nm23H1, chick DRG neurite outgrowth was extensive and effectively limited to the location of the Nm23H1, i.e. neuronal growth cones turned away from adjacent collagen-coated substrata. Nm23H1-coated substrata also significantly enhanced rat DRG neuronal cell adhesion and neurite outgrowth in comparison to collagen-coated substrata. These effects were independent of NGF supplementation. Recombinant Nm23H1 (H118F), which does not possess NDP kinase activity, exhibited the same activity as the wild-type protein. Hence, a novel neuro-stimulatory activity for extracellular Nm23H1 has been identified in vitro, which may function in developing neuronal systems.     

Heteronuclear NMR identifies a nascent helix in intrinsically disordered dynein intermediate chain: implications for folding and dimerization

The intermediate chain of dynein forms a tight subcomplex with dimeric light chains LC8 and Tctex-1, and together they constitute the cargo attachment complex. There is considerable interest in identifying the role of these light chains in the assembly of the two copies of the intermediate chain. The N-terminal domain of the intermediate chain, IC1-289, contains the binding sites for the light chains, and is a highly disordered monomer but gains helical structure upon binding to light chains LC8 and Tctex-1. To provide insights into the structural and dynamic changes that occur in the intermediate chain upon light chains binding, we have used NMR spectroscopy to compare the properties of two distinct sub-domains of IC1-289: IC84-143 which is the light chains binding domain, and IC198-237, which contains a predicted coiled coil necessary for the increase in ordered structure upon light chain binding. Neither construct has stable secondary structure when probed by circular dichroism and amide chemical shift dispersion. Specific residues of IC84-143 involved in binding to the light chains were identified by their increase in resonance line broadening and the corresponding large intensity reduction in 1H-15N HSQC spectra. Interestingly, IC84-143 shows no sign of structure formation after binding to either LC8 or Tctex-1 or to both. IC198-237, on the other hand, contains a population of a nascent helix at low temperature as identified by heteronuclear NMR relaxation measurements, secondary chemical shifts, and sequential amide-amide connectivities. These data are consistent with a model for light chain binding coupled to intermediate chain dimerization through forming a coiled coil distant from the binding site.     

Distinct Kinase-Independent Role of RIPK3 in CD11c+ Mononuclear Phagocytes in Cytokine-Induced Tissue Repair

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