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Author: Ihling, Christian ×

Publications Search Results

Now showing 1 - 3 of 3
  • Publication
    A Diazirine-Modified Membrane Lipid to Study Peptide/Lipid Interactions - Chances and Challenges
    ( 2021)
    Dorner, Julia
    ;
    Korn, Patricia
    ;
    Gruhle, Kai
    ;
    Ramsbeck, Daniel
    ;
    Garamus, Vasil M.
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    Lilie, Hauke
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    Meister, Annette
    ;
    Schwieger, Christian
    ;
    Ihling, Christian
    ;
    Sinz, Andrea
    ;
    Drescher, Simon
    Although incorporation of photo-activatable lipids into membranes potentially opens up novel avenues for investigating interactions with proteins, the question of whether diazirine-modified lipids are suitable for such studies, remains under debate. Focusing on the potential for studying lipid/peptide interactions by cross-linking mass spectrometry (XL-MS), we developed a diazirine-modified lipid (DiazPC), and examined its behaviour in membranes incorporating the model a-helical peptide LAVA20. We observed an unexpected backfolding of the diazirine-containing stearoyl chain of the lipid. This surprising behaviour challenges the potential application of DiazPC for future XL-MS studies of peptide and protein/lipid interactions. The observations made for DiazPC most likely represent a general phenomenon for any type of membrane lipids with a polar moiety incorporated into the alkyl chain. Our finding is therefore of importance for future protein/lipid interaction studies relying on modified lipid probes.
  • Publication
    Formation of HERV-K and HERV-Fc1 envelope family members is suppressed on transcriptional and translational level
    ( 2020)
    Gröger, Victoria
    ;
    Wieland, Lisa
    ;
    Naumann, Marcel
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    Meinecke, Ann-Christin
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    Meinhardt, Beate
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    Roßner, Steffen
    ;
    Ihling, Christian
    ;
    Emmer, Alexander
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    Staege, Martin S.
    ;
    Cynis, Holger
    The human genome comprises 8% sequences of retroviral origin, so-called human endogenous retroviruses (HERVs). Most of these proviral sequences are defective, but some possess open reading frames. They can lead to the formation of viral transcripts, when activated by intrinsic and extrinsic factors. HERVs are thought to play a pathological role in inflammatory diseases and cancer. Since the consequences of activated proviral sequences in the human body are largely unexplored, selected envelope proteins of human endogenous retroviruses associated with inflammatory diseases, namely HERV-K18, HERV-K113, and HERV-Fc1, were investigated in the present study. A formation of glycosylated envelope proteins was demonstrated in different mammalian cell lines. Nevertheless, protein maturation seemed to be incomplete as no transport to the plasma membrane was observed. Instead, the proteins remained in the ER where they induced the expression of genes involved in unfolded protein response, such as HSPA5 and sXBP1. Furthermore, low expression levels of native envelope proteins were increased by codon optimization. Cell-free expression systems showed that both the transcriptional and translational level is affected. By generating different codon-optimized variants of HERV-K113 envelope, the influence of single rare t-RNA pools in certain cell lines was demonstrated. The mRNA secondary structure also appears to play an important role in the translation of the tested viral envelope proteins. In summary, the formation of certain HERV proteins is basically possible. However, their complete maturation and thus full biologic activity seems to depend on additional factors that might be disease-specific and await elucidation in the future.
  • Publication
    The correlation of genome size and DNA methylation rate in metazoans
    ( 2013)
    Lechner, Marcus
    ;
    Marz, Manja
    ;
    Ihling, Christian
    ;
    Sinz, Andrea
    ;
    Stadler, Peter F.
    ;
    Krauss, Veiko
    Total DNA methylation rates are well known to vary widely between different metazoans. The phylogenetic distribution of this variation, however, has not been investigated systematically. We combine here publicly available data on methylcytosine content with the analysis of nucleotide compositions of genomes and transcriptomes of 78 metazoan species to trace the evolution of abundance and distribution of DNA methylation. The depletion of CpG and the associated enrichment of TpG and CpA dinucleotides are used to infer the intensity and localization of germline CpG methylation and to estimate its evolutionary dynamics. We observe a positive correlation of the relative methylation of CpG motifs with genome size. We tested this trend successfully by measuring total DNA methylation with LC/MS in orthopteran insects with very different genome sizes: house crickets, migratory locusts and meadow grasshoppers. We hypothesize that the observed correlation between methylation rate and genome size is due to a dependence of both variables from long-term effective population size and is driven by the accumulation of repetitive sequences that are typically methylated during periods of small population sizes. This process may result in generally methylated, large genomes such as those of jawed vertebrates. In this case, the emergence of a novel demethylation pathway and of novel reader proteins for methylcytosine may have enabled the usage of cytosine methylation for promoter-based gene regulation. On the other hand, persistently large populations may lead to a compression of the genome and to the loss of the DNA methylation machinery, as observed, e.g., in nematodes.