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  • 1
    Publikationsdatum: 2013-10-15
    Beschreibung: Post-transcriptional modifications are essential to the cell life cycle, as they affect both pre-ribosomal RNA processing and ribosome assembly. The box C/D ribonucleoprotein enzyme that methylates ribosomal RNA at the 2'-O-ribose uses a multitude of guide RNAs as templates for the recognition of rRNA target sites. Two methylation guide sequences are combined on each guide RNA, the significance of which has remained unclear. Here we use a powerful combination of NMR spectroscopy and small-angle neutron scattering to solve the structure of the 390 kDa archaeal RNP enzyme bound to substrate RNA. We show that the two methylation guide sequences are located in different environments in the complex and that the methylation of physiological substrates targeted by the same guide RNA occurs sequentially. This structure provides a means for differential control of methylation levels at the two sites and at the same time offers an unexpected regulatory mechanism for rRNA folding.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lapinaite, Audrone -- Simon, Bernd -- Skjaerven, Lars -- Rakwalska-Bange, Magdalena -- Gabel, Frank -- Carlomagno, Teresa -- England -- Nature. 2013 Oct 24;502(7472):519-23. doi: 10.1038/nature12581. Epub 2013 Oct 13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24121435" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Apoproteins/chemistry/metabolism ; Archaeal Proteins/chemistry/metabolism ; Biocatalysis ; Chromosomal Proteins, Non-Histone/metabolism ; Methylation ; Models, Molecular ; Multiprotein Complexes/chemistry/metabolism ; Nucleic Acid Conformation ; Pyrococcus furiosus/*enzymology/*genetics ; RNA Folding ; *RNA Processing, Post-Transcriptional ; RNA, Archaeal/chemistry/genetics/metabolism ; RNA, Guide/chemistry/genetics/metabolism ; RNA, Ribosomal/*chemistry/*metabolism ; Ribonucleoproteins, Small Nucleolar/*chemistry/*metabolism
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2012-12-14
    Beschreibung: DNA methyltransferases catalyse the transfer of a methyl group from the ubiquitous cofactor S-adenosyl-L-methionine (AdoMet) onto specific target sites on DNA and play important roles in organisms from bacteria to humans. AdoMet analogs with extended propargylic side chains have been chemically produced for methyltransferase-directed transfer of activated groups (mTAG) onto DNA, although the efficiency of reactions with synthetic analogs remained low. We performed steric engineering of the cofactor pocket in a model DNA cytosine-5 methyltransferase (C5-MTase), M.HhaI, by systematic replacement of three non-essential positions, located in two conserved sequence motifs and in a variable region, with smaller residues. We found that double and triple replacements lead to a substantial improvement of the transalkylation activity, which manifests itself in a mild increase of cofactor binding affinity and a larger increase of the rate of alkyl transfer. These effects are accompanied with reduction of both the stability of the product DNA–M.HhaI–AdoHcy complex and the rate of methylation, permitting competitive mTAG labeling in the presence of AdoMet. Analogous replacements of two conserved residues in M.HpaII and M2.Eco31I also resulted in improved transalkylation activity attesting a general applicability of the homology-guided engineering to the C5-MTase family and expanding the repertoire of sequence-specific tools for covalent in vitro and ex vivo labeling of DNA.
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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