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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 63 (1994), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Highly purified casein kinase II (CK II) isozymes from bovine brain gray matter (BBGM) were obtained by means of a new purification procedure consisting of one phosphocellulose and three Mono-Q steps. The phosphocellulose eluate showed two BBGM-CK II activities. The first minor component (BBGM-CK IIa) was eluted with 0.9 M NaCl and the major component was eluted at 1.1 M NaCl (BBGM-CK IIb). The protein complexes responsible for these two activities were comprised of three subunits, i.e., α (40 kDa), α′ (38 kDa), and β (28 kDa), with various subunit ratios. The two isozymes displayed the same behavior on Superose 12 fast protein liquid chromatographic gel filtration and sucrose density centrifugation. BBGM-CK IIa and b showed chromatographic and biochemical differences including differing Km for ATP and GTP and Ki for heparin and 2,3-bisphosphoglycerate. The properties of the main peak (BBGM-CK IIb) were studied in detail. The stimulatory effect of Mg2+, Mn2+, and Co2+ was highly dependent both on the nature of the substrate and on ionic type and concentration. It is surprising that with phosvitin as substrate, BBGM-CK IIb was fully active even in the absence of Mg2+ and NaCl. The inhibitory effect of heparin and the stimulatory effects of NaCl, KCl, spermine, and polylysine were highly dependent on the ionic strength, buffer type, and substrate. BBGM-CK II isozymes phosphorylated stathmine in the presence of polylysine, but the requirement for polybasic compounds was not absolute, as is the case with calmodulin and clathrin β-light chain. The unusual chromatographic behavior and biochemical properties of these BBGM-CK II isozymes, compared with the classical CK II, could be explained at least in part by their subunit ratios.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature biotechnology 21 (2003), S. 1451-1452 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Animal cloning by nuclear transfer is known to be inefficient. Cloned embryos are associated with low rates of pregnancy and birth as well as a high proportion of abnormal newborns. A recent study of mouse clones by Boiani et al. helps explain these phenomena and shows that the simple procedure of ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4935
    Keywords: Protein kinase inhibitors ; prolactin ; milk protein genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Two protein kinase-inhibitors, 6-dimethyl amino purine and 2-amino purine inhibited induction of β-casein synthesis by prolactin when added to the culture medium of rabbit mammary explant and cells. The accumulation of the mRNA for αs1- and β-caseins and for whey acidic protein did not take place in the presence of the inhibitors whereas β-actin mRNA concentration was not altered. In the same experimental conditions, H7, an inhibitor of protein kinase C and, to a lower extent, of protein kinase A did not prevent prolactin from acting. These data suggest for the first time that specific protein kinases are involved in the transduction of the prolactin signal to milk protein genes.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4978
    Keywords: MAR ; SCS ; insulation ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The flanking sequences of several genes have been shown to direct a position independent expression of transgenes. Attempts to completely identify the insulating sequences have failed so far. Some of these sequences contain a matrix attached region (MAR) located in the flanking part of the genes. This article will show that the MARs in cultured cells located in the 3' OH region of the human apolipoprotein B100 (Apo B100) and within the SV40 genome were unable to stimulate and insulate transgene expression directed by the promoters from a rabbit whey acidic protein (WAP) gene or from human cytomegalovirus (hCMV) early genes. In transgenic mice, the MAR from the Apo B100 and SV40 genes did not enhance the expression of a transgene containing the rabbit whey acid protein (WAP) promotor, the late gene SV40 intron (VP1 intron), the bovine growth hormone (bGH) cDNA and the SV40 late gene terminator. This construct was even toxic for embryos. Similarly, the specialized chromatin structure (SCS) from the Drosophila 87A7 HSP70 gene reduced chloramphenicol acetyl transferase (CAT) activity when added between a cytomegalovirus (CMV) enhancer and a Herpes simplex thymidine kinase (TK) gene promoter. This inhibitory action was almost complete when a second SCS sequence was added before the CMV enhancer. Sequences from the firefly luciferase and from the human gene cathepsin D cDNA used as control unexpectedly showed a similar inhibitory effect when added to the CMVTKCAT construct instead of SCS. When added before the CMV enhancer and after the transcription terminator in the CMVTKCAT construct, the SCS sequence was unable to insulate the integrated gene as seen by the fact that the level of CAT in cell extracts were by no means correlated with the number of copies in individual clones. From these data, it is concluded that i) a MAR containing the canonical AT rich sequences does not amplify the expression of all gene constructs ii) AT rich MAR sequences do not have per se an insulating effect iii) Drosophila SCS from the 87A7 HSP70 gene has no insulating effect in all gene constructs (at least in mammalian cells) iv) and the addition of a DNA fragment between an enhancer and a promoter in a gene construct cannot be used as a reliable test to evaluate its insulating property.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4978
    Keywords: IRES ; translation ; monocistronic mRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The IRES from poliovirus and from encephalomyocarditis virus (EMCV) added between the cap and the AUG initiator codon were strong inhibitors of chloramphenicol acetyltransferase gene expression in three different cell types. The poliovirus IRES also inhibited bGH (bovine growth hormone) cDNA expression in the HC11 mammary cell line when added between the rabbit whey acidic gene promoter and the cDNA whereas the HTLV-1 IRES showed a stimulatory effect in the same situation. RNA stem loops were added before HTLV-1 (SUR) and the BiP (Immunoglobulin heavy-chain Binding Protein) IRESs followed by the firefly luciferase gene under the control of Rous sarcoma virus (RSV) promoter. The RNA loops abolished the expression of the reporter gene almost completely. These data suggest that the different IRESs may favour or inhibit translation of monocistronic mRNA.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-9368
    Keywords: mammary gland ; promoter ; regulatory elements ; lactation ; pregnancy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 5′ flanking region (6.3 kb) of the rabbit WAP (rWAP) gene possesses important regulatory elements. This region was linked to the human growth hormone (hGH) structural gene in order to target transgene expression to the mammary gland. Thirteen lines of transgenic mice were produced. Milk could be collected from six lines of transgenic mice. In five of them, hGH was present in the milk at high concentrations ranging from 4 to 22 mg ml−1. hGH produced by the mammary gland comigrated with hGH of human origin. It was biologically active, and through its prolactin-like activity induced lactogenesis when introduced into mammary culture media. Two of these mouse lines were studied further. hGH mRNA was only detected in the mammary gland during lactation. In the seven other transgenic lines, hGH was present in the blood of cyclic females. The prolactin-like effect of hGH in these mice probably induced female sterility, and milk could, therefore not be obtained. In two lines studied in more detail, the mammary gland was the main organ producing hGH, even in cyclic mice. Low ectopic expression was detected in other organs which varied from one line to the other. This was probably due to the influence on the transgene of the site of integration into the mouse genome. In the 13 lines studied, high mammary-specific hGH expression was not correlated to the transgene copy number. The rWAP-hGH construct thus did not behave as an independent unit of transcription. However, it can be concluded that the 6.3 kb flanking region of the rWAP gene contains regulatory elements responsible for the strong mammary-specific expression of hGH transgene, and that it is a good candidate to control high levels of foreign protein gene expression in the mammary gland of lactating transgenic animals.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-9368
    Keywords: DNA extraction ; glass powder ; PCR ; transgene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A very simple and reliable method to extract DNA directly from mouse tail, rabbit ear and blood is described. Tissue was homogenized in a solution of NaI and the DNA was extracted using glass powder. The extracted DNA was obtained in sufficient quantity and purity to allow direct detection of transgene by PCR.
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  • 8
    ISSN: 1573-9368
    Keywords: transgenic rabbits ; β‐globin 5′HS4 ; CD55 cDNA ; CD59 cDNA ; xenotransplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Whatever its field of application, animal transgenesis aims at a high level of reproducible and stable transgene expression. In the case of xenotransplantation, prevention of hyperacute rejection of grafts of animal origin requires the use of organs expressing human inhibitors of complement activation such as CD55 (DAF) and CD59. Pigs transgenic for these molecules have been produced, but with low and variable levels of expression. In order to improve cDNA expression, a vector containing the 5′HS4 region from the LCR of the chicken β‐globin locus and the promoter and the first intron from the human EF1α gene, was used to co‐express human CD55 and CD59 cDNAs in transgenic rabbits. The transgenic lines with the 5′HS4 region displayed dramatically enhanced CD55 and CD59 mRNA concentrations in brain, heart, kidney, liver, lung, muscle, spleen and aortic endothelial cells in comparison with the transgenic lines without the 5′HS4 region. In the absence of the 5′HS4 region, only some of the transgenic lines displayed specific mRNAs and at low levels. Human CD55 and CD59 proteins were detectable in mononuclear cells from transgenic rabbits although at a lower level than in human mononuclear cells. On the other hand, primary aortic endothelial cells from a bi‐transgenic line were very efficiently protected in vitro against human complement‐dependent lysis. Transgenic rabbits harbouring the two human inhibitors of complement activation, CD55 and CD59, can therefore be used as new models in xenotransplantation. Moreover, the vector containing the 5′HS4 region from the LCR of the chicken β‐globin locus seems appropriate not only for xenotransplantation but also for any other studies involving transgenic animals in which cDNAs have to be expressed at a high level in all cell types.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-9368
    Keywords: superoxide dismutase ; recombinant protein ; transgeneexpression ; metalloprotein ; gene expression ; transgenic rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression of human extracellular superoxide dismutase (EC-SOD), a glycosylated, tetrameric metalloprotein, was targeted to the lactating mammary gland of transgenic rabbits. Efficient expression of the recombinant whey acidic protein/ec-sod gene was achieved and up to 3 mg ml−1 of the enzyme was secreted into the milk. Rabbit milk-produced recombinant EC-SOD was primarily found in the whey and purified by a two-step chromatographic method. To evaluate the rabbit milk-produced human EC-SOD, comparisons with native and Chinese hamster ovary cell (CHO)-produced EC-SOD were performed. All proteins were tetrameric and N-glycosylated. The behaviour on SDS-PAGE and size-exclusion chromatography indicated that the masses, and thereby the extent of post-translational modification of the proteins was similar. The monosaccharide composition of both recombinant EC-SOD variants was analysed and indicated similarities in the attached N-glycans on the two proteins. Furthermore, the peptide maps of the three EC-SOD variants revealed that all proteins had similar polypeptide backbones
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Transgenic research 8 (1999), S. 157-177 
    ISSN: 1573-9368
    Keywords: IRES ; mechanism of action ; ribosomes ; scanning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract IRESs are known to recruit ribosomes directly, without a previous scanning of untranslated region of mRNA by the ribosomes. IRESs have been found in a number of viral and cellular mRNAs. Experimentally, IRESs are commonly used to direct the expression of the second cistrons of bicistronic mRNAs. The mechanism of action of IRESs is not fully understood and a certain number of laboratories were not successful in using them in a reliable manner. Three observations done in our laboratory suggested that IRESs might not work as functionally as it was generally believed. Stem loops added before IRESs inhibited mRNA translation. When added into bicistronic mRNAs, IRESs initiated translation of the second cistrons efficiently only when the intercistronic region contained about 80 nucleotides, and they did not work any more effectively with intercistronic regions containing at least 300–400 nucleotides. Conversely, IRESs inserted at any position into the coding region of a cistron interrupted its translation and initiated translation of the following cistron. The first two data are hardly compatible with the idea that IRESs are able to recruit ribosomes without using the classical scanning mechanism. IRESs are highly structured and cannot be scanned by the 40S ribosomal subunit. We suggest that IRESs are short‐circuited and are essentially potent stimulators favoring translation in particular physiological situations.
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