HDAC inhibitors induce apoptosis but not cellular senescence in Gadd45α-deficient E1A+Ras cells

HDAC inhibitors (HDIs) induce irreversible cell cycle arrest and senescence in E1A+Ras expressing cells. Furthermore, HDIs activate Gadd45α/NF-κB signaling pathway to suppress apoptosis thereby promoting the cell survival. Here, to clarify the role of Gadd45α in realization of the antiapoptotic program, we compared wild-type E1A+Ras cells and the cells with knockout of gadd45α gene (Gadd45α−/− cells). As in Gadd45α-expressing E1A+Ras cells, HDIs induce irreversible cell cycle arrest in Gadd45α−/− cells, but the arrested cells do not senesce and eventually die due to activation of the apoptotic death program. These data suggest that the expression of Gadd45α is involved in maintaining the balance of pro- and anti-apoptotic stimuli, while lack or loss of Gadd45 directs the cells to apoptosis after HDIs treatment. Appropriately Gadd45α-deficient cells demonstrate a higher level of pro-apoptotic signals, whereas the anti-apoptotic program is suppressed. The elevated apoptotic background of Gadd45α−/− cells is accompanied by higher levels of Ser15-phosphorylated p53 and p21/Waf1 proteins that additionally commit the cells to HDIs-induced apoptosis. Additionally, loss of Gadd45α protein activates the DDR signaling pathway as demonstrated by nuclear pATM staining, accumulation of γH2AX foci and an increase of single-strand DNA breaks. Thus, in wild-type E1A+Ras cells the p53-dependent expression of Gadd45α is necessary not only for DNA repair and HDI-induced cellular senescence, but also to withstand to apoptosis after DNA damage and stress. Therefore the use of HDIs in combination with agents that block Gadd45α function may have promise for cancer therapy.     

Soluble HLA-DQ2 expressed in S2 cells copurifies with a high affinity insect cell derived protein

We here describe that soluble HLA-DQ2 (sDQ2) molecules, when expressed in Drosophila melanogaster S2 insect cells without a covalently tethered peptide, associate tightly with the D. melanogaster calcium binding protein DCB-45. The interaction between the proteins is stable in S2 cell culture and during affinity purification, which is done at high salt concentrations and pH 11.5. After affinity purification, the sDQ2/DCB-45 complex exists in substantial quantities next to a small amount of free heterodimeric sDQ2 and large amounts of aggregated sDQ2 free of DCB-45. Motivated by the stable complex formation and our interest in the development of reagents which inhibit HLA-DQ2 peptide binding, we have further characterized the sDQ2/DCB-45 interaction. Several lines of evidence indicate that an N-terminal fragment of DCB-45 is involved in the interaction with the peptide binding groove of sDQ2. Further mapping of this fragment of 54 residues identified a pentadecapeptide with high affinity for sDQ2 which may serve as a lead compound for the design of HLA-DQ2 blockers.     

豆科三属八种植物的核型及rDNA定位研究

对豆科槐属的国槐(SophorajaponicaL.)、五叶槐(S.japonicaL.f.oligophyllaFranch.)、龙爪槐(S.japonicaL.f·pendulaLoud.)、黄金槐(S.xanthanthaC.Y.Ma.)(以上均为四倍体,2n=4x=28)、红花槐(S.rubrifloraTsoong.,2n=3x=21),刺槐属的刺槐(Robiniapseudoa-caciaL.,2n=2x=22)、毛洋槐(R.hispidaL.,2n=2x=30)和紫穗槐属的紫穗槐(AmorphafruticosaL.,2n=2x=40)核型进行了分析,并应用荧光原位杂交技术进行了45SrDNA的染色体定位。槐属4个四倍体种各具4个45SrDNA位点,位于两对染色体的着丝粒周围;红花槐,3个45SrDNA位点位于第5组染色体随体区域。刺槐,4个rDNA位点位于两对随体染色体端部;毛洋槐,8个rDNA位点,4个位于两对染色体的随体及次缢痕,另4个位于两对染色体着丝粒周围。紫穗槐,6个45SrDNA位点,分别位于3对染色体的着丝粒和随体。本文对rDNA作为染色体标记在核型分析中的应用及在基因组中的分布特点进行了讨论。     

Mechanisms to avoid photoinhibition in a desiccation-tolerant cyanobacterium, Nostoc commune

A desiccation-tolerant cyanobacterium, Nostoc commune, showsunique responses to dehydration. These responses are: (i) lossof PSII activity in parallel with the loss of photosynthesis;(ii) loss of PSI activity; and (iii) dissipation of light energyabsorbed by pigment–protein complexes. In this study,the deactivation of PSII is shown to be important in avoidingphotoinhibition when the Calvin–Benson cycle is repressedby dehydration. Furthermore, our evidence suggests that dissipationof light energy absorbed by PSII blocks photoinhibition understrong light in dehydrated states.     

黄褐棉45S rDNA的FISH定位及核型分析

黄褐棉是棉属5个四倍体棉种之一,利用荧光原位杂交技术将45S rDNA定位在黄褐棉2、4、9号染色体,2号染色体上的45S rDNA特别大,信号位于随体并覆盖了染色体的短臂,比二倍体和四倍体棉种的45SrDNA都要大得多;另外的2对信号很小,形状与陆地棉中的弱信号类似。黄褐棉的核型公式为：2n=4x=52=50m（2SAT）＋2sm,属于2B类型,第2对染色体为亚中着丝粒染色体,其余都为中部着丝粒染色体。黄褐棉的核型、随体数、45S rDNA与其他四倍体棉种区别很大,黄褐棉是一个非常特殊的四倍体棉种。     

Immunochemical analysis of the carbohydrate moiety of yeast killer toxin K28

Killer toxin K₂₈, a 16 kd protein secreted by the wine yeast Saccharomyces cerevisiae strain 28, was reversibly bound by a column of Concanavalin A-Sepharose, confirming its glycoprotein nature. HPLC analysis of acid hydrolyzates of K₂₈ toxin as well as Western-blots of -eliminated and/or endo H-treated killer toxin preparations probed with polyclonal -toxin antibodies revealed that the carbohydrate moiety of K₂₈ consists of D-mannose only, which is O-glycosidically linked via Ser/Thr residues to the protein part. The change in gel mobility of K₂₈ after -elimination was caused by a decrease in molecular mass of about 1,800, corresponding to a carbohydrate moiety of 10 mannose residues per killer toxin molecule.     

Sequence of the gene for a NAD(P)-dependent formaldehyde dehydrogenase (class III alcohol dehydrogenase) from a marine methanotroph Methylobacter marinus A45

Abstract A fragment of Methylobacter marinus A45 DNA has been cloned and sequenced, and an open reading frame has been identified that could code for a 46-kDa polypeptide. Comparison of the deduced amino acid sequence of the polypeptide against the protein data bank has revealed strong similarity with a number of alcohol dehydrogenases, with highest similarity towards class III alcohol dehydrogenases, which recently have been shown to be identical to glutathione-dependent formaldehyde dehydrogenases. We were unable to measure appreciable levels of NAD(P)-dependent formaldehyde dehydrogenases or alcohol dehydrogenase activities using aldehydes or primary or secondary alcohols in cell-free extracts from batch cultures of M. marinus A45. However, formaldehyde dehydrogenases activity was detected on zymograms. Our data suggest that, although NAD(P)-linked formaldehyde dehydrogenase or alcohol dehydrogenase activities are undetectable in cell-free extracts of most methylotrophs employing the ribulose monophosphate pathway for formaldehyde assimilation and dissimilation, the gene encoding formaldehyde dehydrogenase is present in M. marinus A45 and may be present in more of these organisms as well.     

UNC-45 is required for NMY-2 contractile function in early embryonic polarity establishment and germline cellularization in C. elegans

The Caenorhabditis elegans UNC-45 protein is required for proper body wall muscle assembly and acts as a molecular co-chaperone for type II myosins. In contrast to other body wall muscle components, UNC-45 is also abundant in the germline and embryo. We show that maternally provided UNC-45 acts with non-muscle myosin II (NMY-2) during embryonic polarity establishment, cytokinesis and germline cellularization. In embryos depleted for UNC-45, myosin contractility is eliminated resulting in embryonic defects in polar body extrusion, cytokinesis and establishment of polarity. Despite a lack of contractility in an unc-45(RNAi) embryo, NMY-2::GFP localizes to the cortex and accumulates at the presumptive cytokinetic furrow indicating that UNC-45 is not required for cortical localization. UNC-45 and NMY-2 are also required for fertility since the lack of either component results in complete sterility due to failed initiation of the cellularization furrows that separate syncytial nuclei into germ cells. In the absence of UNC-45, the actomyosin cytoskeleton does not contract despite non-functional myosin still directly binding actin. UNC-45 has been previously suggested to be required for the folding of the myosin head, and our results refine this hypothesis suggesting that UNC-45 is not required to fold or maintain the actin binding domain but is still required for myosin function.     

腹泻仔猪大肠埃希菌分离株ST4214的全基因组测序分析

分析腹泻仔猪大肠埃希菌(E.coli)分离株血清型、毒力因子及耐药基因。

本课题组前期研究从腹泻仔猪粪便样本中分离到64株E.coli, 本研究取其中含有毒力因子最多的1株进行全基因组测序分析。

E.coli分离株基因组序列为5.5 Mb, 预测蛋白质编码序列数为5 743, 与已知致病菌E.coli O145的基因重合率较低, 为64.53%。经多位点序列分型分析, 确定分离株为E.coli ST4214, 血清型为O3∶H45。与病原菌O157∶H7、O145∶H28和O104∶H4的毒力基因比较表明: 4株菌共同含有的毒力基因为354个, E.coli ST4214含有64种独特的毒力基因、编码鞭毛蛋白、Ⅳ型分泌蛋白、Ⅱ型分泌蛋白、溶血素、菌毛、肠毒素、荚膜多糖相关蛋白质。耐药基因E.coli分离株含有氨基香豆素抗性基因、磺胺类耐药基因、β-内酰胺抗性基因、多粘菌素耐药基因、肽抗生素抗性基因和抗生素耐药基因外排泵等多重耐药基因。

腹泻仔猪E.coli ST4214分离株是一株新菌株, 具有较多毒力因子及耐药基因, 可能与仔猪腹泻发病相关。