脑损伤

    DNAzyme as a rising gene-silencing agent in theranostic settings
  • Figure 1|Sequence and structure of 8–17 (A and B) and 10–23 (C and D) DNAzymes (PDB entries 5XMA and 1BR2). 

    Modus operandi: The best characterized DNAzymes to date are 8–17 and 10–23; both were discovered and enriched by iterative SELEX cycles from a library of 1014 chimeric molecules, each containing a 5′-biotin, 12 target ribonucleotides, and 50 random deoxynucleotides (N50) (Santoro and Joyce, 1997). DNAzymes generally have a catalytic core flanked by two RNA bindings arms for target recognition. Target cleavage is initiated by metal-assisted deprotonation of 2′-hydroxyl in the RNA, generating a 2′,3′-cyclic phosphate upstream and a 5′-hydroxyl downstream, reminiscent of unrepaired “dirty” ends. The 8–17 DNAzyme specifically cleaves at A│G dinucleotide junctions in the presence of Mg2+, Mn2+, Zn2+, Ca2+ or Pb2+. The compatibility of 8–17 with several biologically relevant cations may benefit its catalytic efficiency at a cellular level. The crystal structure of 8–17 unexpectedly revealed long-range base-pairing events that supported a catalytic pseudoknot. These long-range interactions include a Watson-Crick G6–C12 base pair and a non-canonical Hoogsten-sugar edge A5-G13 base pair (Figure 1A and B), whose substitutions completely abolish DNAzyme function (Wang et al., 2010). In contrast to 8–17, the 10–23 DNAzyme cuts RNA at any purine-pyrimidine dinucleotide junction (R│Y with R = A/G; Y = U/C), potentially offering a broader range of targetability. The folding of 10–23 preceding catalysis is also driven by increasing ionic concentration but the mechanism remains poorly understood. One structural study suggests that two 10–23 DNAzymes and two RNA targets collectively form a five double-helical bundle, which could yield a catalytically inactive conformation (PDB entry: 1BR3). Despite the apparent topological differences, both 8–17 and 10–23 share highly conserved residues (Figure 1A and C), and 10–23 might be a structural variant of 8–17 (Wang et al., 2010).


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  • 发布日期: 2022-03-10  浏览: 292
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