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  • 1
    Online Resource
    Online Resource
    Emergent rules for codon choice elucidated by editing rare arginine codons in Escherichia coli
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 38 ( 2016-09-20)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 38 ( 2016-09-20)
    Abstract: The degeneracy of the genetic code allows nucleic acids to encode amino acid identity as well as noncoding information for gene regulation and genome maintenance. The rare arginine codons AGA and AGG (AGR) present a case study in codon choice, with AGRs encoding important transcriptional and translational properties distinct from the other synonymous alternatives (CGN). We created a strain of Escherichia coli with all 123 instances of AGR codons removed from all essential genes. We readily replaced 110 AGR codons with the synonymous CGU codons, but the remaining 13 “recalcitrant” AGRs required diversification to identify viable alternatives. Successful replacement codons tended to conserve local ribosomal binding site-like motifs and local mRNA secondary structure, sometimes at the expense of amino acid identity. Based on these observations, we empirically defined metrics for a multidimensional “safe replacement zone” (SRZ) within which alternative codons are more likely to be viable. To evaluate synonymous and nonsynonymous alternatives to essential AGRs further, we implemented a CRISPR/Cas9-based method to deplete a diversified population of a wild-type allele, allowing us to evaluate exhaustively the fitness impact of all 64 codon alternatives. Using this method, we confirmed the relevance of the SRZ by tracking codon fitness over time in 14 different genes, finding that codons that fall outside the SRZ are rapidly depleted from a growing population. Our unbiased and systematic strategy for identifying unpredicted design flaws in synthetic genomes and for elucidating rules governing codon choice will be crucial for designing genomes exhibiting radically altered genetic codes.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1605856113
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
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  • 2
    Online Resource
    Online Resource
    Recombinant hepatitis E virus genomes infectious for primates: Importance of capping and discovery of a cis-reactive element
    Proceedings of the National Academy of Sciences ; 2001
    In:  Proceedings of the National Academy of Sciences Vol. 98, No. 26 ( 2001-12-18), p. 15270-15275
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 98, No. 26 ( 2001-12-18), p. 15270-15275
    Abstract: Hepatitis E virus recombinant genomes transcribed in vitro from two cDNA clones differing by two nucleotides were infectious for chimpanzees. However, one cDNA clone encoded a virus that was attenuated for chimpanzees and unable to infect rhesus monkeys. The second cDNA clone encoded a virus that infected both chimpanzees and rhesus monkeys and caused acute hepatitis in both. One mutation differentiating the two clones identified a cis-reactive element that appeared to overlap the 3′ end of the capsid gene and part of the 3′ noncoding region. Capping of the RNA transcripts was essential for infectivity.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.251555098
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2001
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
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  • 3
    Online Resource
    Online Resource
    Prevention of hepatitis C virus infection in chimpanzees after antibody-mediated in vitro neutralization.
    Proceedings of the National Academy of Sciences ; 1994
    In:  Proceedings of the National Academy of Sciences Vol. 91, No. 16 ( 1994-08-02), p. 7792-7796
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 91, No. 16 ( 1994-08-02), p. 7792-7796
    Abstract: Hepatitis C virus (HCV) is the most important etiologic agent of non-A, non-B hepatitis and is a major cause of chronic liver disease and hepatocellular carcinoma. Development of an effective vaccine would be the most practical method for prevention of the infection, but whether infection with HCV elicits protective immunity in the host is unclear. Neutralization of HCV in vitro was attempted with plasma of a chronically infected patient, and the residual infectivity was evaluated by inoculation of eight seronegative chimpanzees. The source of HCV was plasma obtained from a patient during the acute phase of posttransfusion non-A, non-B hepatitis, which had previously been titered for infectivity in chimpanzees. Neutralization was achieved with plasma obtained from the same patient 2 yr after the onset of primary infection but not with plasma obtained 11 yr later, although both plasmas contained antibodies against nonstructural and structural (including envelope) HCV proteins. Analysis of sequential viral isolates from the same patient revealed significant genetic divergence as early as 2 yr after infection. However, the HCV recovered from the patient 2 yr after the infection had a striking sequence similarity with the HCV recovered from one of the chimpanzees inoculated with the acute-phase virus, suggesting that the progenitor of the new strain was already present 2 yr earlier. This evidence, together with the different sequences of HCV recovered from the chimpanzees that received the same inoculum, confirms that HCV is present in vivo as a quasispecies. These results provide experimental evidence in vivo that HCV infection elicits a neutralizing antibody response in humans but suggest that such antibodies are isolate-specific. This result raises concerns for the development of a broadly reactive vaccine against HCV.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.91.16.7792
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1994
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    detail.hit.zdb_id: 1461794-8
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  • 4
    Online Resource
    Online Resource
    Chitinase 3-like 1 is a profibrogenic factor overexpressed in the aging liver and in patients with liver cirrhosis
    Proceedings of the National Academy of Sciences ; 2021
    In:  Proceedings of the National Academy of Sciences Vol. 118, No. 17 ( 2021-04-27)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 118, No. 17 ( 2021-04-27)
    Abstract: Older age at the time of infection with hepatitis viruses is associated with an increased risk of liver fibrosis progression. We hypothesized that the pace of fibrosis progression may reflect changes in gene expression within the aging liver. We compared gene expression in liver specimens from 54 adult donors without evidence of fibrosis, including 36 over 40 y old and 18 between 18 and 40 y old. Chitinase 3-like 1 ( CHI3L1 ), which encodes chitinase-like protein YKL-40/CHI3L1, was identified as the gene with the greatest age-dependent increase in expression in liver tissue. We investigated the cellular source of CHI3L1 in the liver and its function using liver tissue specimens and in vitro models. CHI3L1 expression was significantly higher in livers of patients with cirrhosis of diverse etiologies compared with controls represented by patients who underwent liver resection for hemangioma. The highest intrahepatic CHI3L1 expression was observed in cirrhosis due to hepatitis D virus, followed by hepatitis C virus, hepatitis B virus, and alcohol-induced cirrhosis. In situ hybridization of CHI3L1 messenger RNA (mRNA) identified hepatocytes as the major producers of CHI3L1 in normal liver and in cirrhotic tissue, wherein hepatocytes adjacent to fibrous septa showed higher CHI3L1 expression than did those in more distal areas. In vitro studies showed that recombinant CHI3L1 promotes proliferation and activation of primary human hepatic stellate cells (HSCs), the major drivers of liver fibrosis. These findings collectively demonstrate that CHI3L1 promotes liver fibrogenesis through a direct effect on HSCs and support a role for CHI3L1 in the increased susceptibility of aging livers to fibrosis progression.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2019633118
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 209104-5
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    SSG: 11
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Directed evolution of gene-shuffled IFN-α molecules with activity profiles tailored for treatment of chronic viral diseases
    Proceedings of the National Academy of Sciences ; 2007
    In:  Proceedings of the National Academy of Sciences Vol. 104, No. 20 ( 2007-05-15), p. 8269-8274
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 104, No. 20 ( 2007-05-15), p. 8269-8274
    Abstract: Type I IFNs are unusually pleiotropic cytokines that bind to a single heterodimeric receptor and have potent antiviral, antiproliferative, and immune modulatory activities. The diverse effects of the type I IFNs are of differential therapeutic importance; in cancer therapy, an enhanced antiproliferative effect may be beneficial, whereas in the therapy of viral infections (such as hepatitis B and hepatitis C), the antiproliferative effects lead to dose limiting bone marrow suppression. Studies have shown that various members of the natural IFN-α family and engineered variants, such as IFN-con1, vary in the ratios between various IFN-mediated cellular activities. We used DNA shuffling to explore and confirm the hypothesis that one could simultaneously increase the antiviral and Th1-inducing activity and decrease the antiproliferative activity. We report IFN-α hybrids wherein the ratio of antiviral:antiproliferative and Th1-inducing: antiproliferative potencies are markedly increased with respsect to IFN-con1 (75- and 80-fold, respectively). A four-residue motif that overlaps with the IFNAR1 binding site and is derived by cross breeding with a pseudogene contributes significantly to this phenotype. These IFN-αs have an activity profile that may result in an improved therapeutic index and, consequently, better clinical efficacy for the treatment of chronic viral diseases such as hepatitis B virus, human papilloma virus, HIV, or chronic hepatitis C.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0609001104
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2007
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Lack of Protective Immunity Against Reinfection with Hepatitis C Virus
    American Association for the Advancement of Science (AAAS) ; 1992
    In:  Science Vol. 258, No. 5079 ( 1992-10-02), p. 135-140
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 258, No. 5079 ( 1992-10-02), p. 135-140
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1279801
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 1992
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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  • 7
    Online Resource
    Online Resource
    Successful passive and active immunization of cynomolgus monkeys against hepatitis E.
    Proceedings of the National Academy of Sciences ; 1994
    In:  Proceedings of the National Academy of Sciences Vol. 91, No. 21 ( 1994-10-11), p. 10198-10202
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 91, No. 21 ( 1994-10-11), p. 10198-10202
    Abstract: Virtually full protection against hepatitis E and partial or complete protection against infection with hepatitis E virus (HEV) were achieved in passively or actively immunized cynomolgus monkeys. Hepatitis, viremia, and shedding of the virus in feces were detected in all nonimmunized animals that were challenged with HEV. HEV titers detected by reverse transcriptase PCR were higher in feces than in serum of nonimmunized animals. Anti-HEV antibody titers at the time of challenge ranged between 1:40 and 1:200 in animals passively immunized with convalescent plasma from a cynomolgus monkey previously infected with HEV and between 1:100 and 1:10,000 in animals actively immunized with a recombinant 55-kDa open reading frame 2 protein. The estimated 50% protective titer of passively acquired anti-HEV antibodies was 1:40. Although only one of four passively immunized animals showed histopathologic evidence of hepatitis, all four were infected after challenge; however, the titers of HEV in serum and feces were lower in the passively immunized animals than in the nonimmunized group. The actively immunized animals developed neither hepatitis nor viremia when challenged with HEV and virus was either not detected or was present in low titer in feces. The protective response was a function of the ELISA anti-HEV antibody titer at the time of challenge and the immunization schedule.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.91.21.10198
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1994
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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