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See detailMiR-128 represses L1 retrotransposition by binding directly to L1 RNA
Hamdorf, Matthias UL; Idica, A.; Zisoulis, D. G. et al

in Nature Structural and Molecular Biology (2015), 22(10), 824-831

Long interspersed element 1 (LINE-1 or L1) retrotransposons compose 17% of the human genome. Active L1 elements are capable of replicative transposition (mobilization) and can act as drivers of genetic ... [more ▼]

Long interspersed element 1 (LINE-1 or L1) retrotransposons compose 17% of the human genome. Active L1 elements are capable of replicative transposition (mobilization) and can act as drivers of genetic diversity. However, this mobilization is mutagenic and may be detrimental to the host, and therefore it is under strict control. Somatic cells usually silence L1 activity by DNA methylation of the L1 promoter. In hypomethylated cells, such as cancer cells and induced pluripotent stem cells (iPSCs), a window of opportunity for L1 reactivation emerges, and with it comes an increased risk of genomic instability and tumorigenesis. Here we show that miR-128 represses new retrotransposition events in human cancer cells and iPSCs by binding directly to L1 RNA. Thus, we have identified and characterized a new function of microRNAs: mediating genomic stability by suppressing the mobility of endogenous retrotransposons. © 2015 Nature America, Inc. All rights reserved. [less ▲]

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See detailThe non-autonomous retrotransposon SVA is trans-mobilized by the human LINE-1 protein machinery
Raiz, J.; Damert, A.; Chira, S. et al

in Nucleic Acids Research (2012), 40(4), 1666-1683

SINE-VNTR-Alu (SVA) elements are non-autonomous, hominid-specific non-LTR retrotransposons and distinguished by their organization as composite mobile elements. They represent the evolutionarily youngest ... [more ▼]

SINE-VNTR-Alu (SVA) elements are non-autonomous, hominid-specific non-LTR retrotransposons and distinguished by their organization as composite mobile elements. They represent the evolutionarily youngest, currently active family of human non-LTR retrotransposons, and sporadically generate disease-causing insertions. Since preexisting, genomic SVA sequences are characterized by structural hallmarks of Long Interspersed Elements 1 (LINE-1, L1)-mediated retrotransposition, it has been hypothesized for several years that SVA elements are mobilized by the L1 protein machinery in trans. To test this hypothesis, we developed an SVA retrotransposition reporter assay in cell culture using three different human-specific SVA reporter elements. We demonstrate that SVA elements are mobilized in HeLa cells only in the presence of both L1-encoded proteins, ORF1p and ORF2p. SVA trans-mobilization rates exceeded pseudogene formation frequencies by 12-to 300-fold in HeLa-HA cells, indicating that SVA elements represent a preferred substrate for L1 proteins. Acquisition of an AluSp element increased the trans-mobilization frequency of the SVA reporter element by ∼25-fold. Deletion of (CCCTCT)n repeats and Alu-like region of a canonical SVA reporter element caused significant attenuation of the SVA trans-mobilization rate. SVA de novo insertions were predominantly full-length, occurred preferentially in G+C-rich regions, and displayed all features of L1-mediated retrotransposition which are also observed in preexisting genomic SVA insertions. © 2012 The Author(s). [less ▲]

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See detailEmploying live microbes for vaccine delivery
Loessner, Holger; Schwantes, Astrid; Hamdorf, Matthias UL et al

in Development of Novel Vaccines: Skills, Knowledge and Translational Technologies (2012)

The employment of live attenuated vaccines has a long-standing record in human and veterinary medicine. Most of the vaccines in current use were empirically developed during the last century. Today, due ... [more ▼]

The employment of live attenuated vaccines has a long-standing record in human and veterinary medicine. Most of the vaccines in current use were empirically developed during the last century. Today, due to the great advances in fields such as immunology and bioengineering, the rational development of live attenuated vaccines becomes increasingly feasible. Moreover, live vaccines can be used as carrier systems for heterologous antigens or therapeutic factors. In each case, the development of a recombinant live attenuated vaccine is a complex task where properties such as targeting specificity, antigen synthesis, antigen release, and safety aspects have to be integrated. A range of such recombinant vaccine candidates have successfully been tested in the clinics, but very few have been approved so far. In many cases, further optimization of such vaccines is necessary with regard to their efficacy and safety profiles. In the present chapter, we focus on current strategies which are employed for the development of new and the optimization of first generation recombinant live vaccines based on bacteria and viruses. © 2012 Springer-Verlag Wien. [less ▲]

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