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2017 ; 45
(3
): 1345-1354
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Nucleobase modification by an RNA enzyme
#MMPMID28180302
Nucleic Acids Res
2017[Feb]; 45
(3
): 1345-1354
PMID28180302
show ga
Ribozymes can catalyze phosphoryl or nucleotidyl transfer onto ribose hydroxyls
of RNA chains. We report a single ribozyme that performs both reactions, with a
nucleobase serving as initial acceptor moiety. This unprecedented combined
reaction was revealed while investigating potential contributions of ribose
hydroxyls to catalysis by kinase ribozyme K28. For a 58nt, cis-acting form of
K28, each nucleotide could be replaced with the corresponding 2?F analog without
loss of activity, indicating that no particular 2?OH is specifically required.
Reactivities of two-stranded K28 variants with oligodeoxynucleotide acceptor
strands devoid of any 2?OH moieties implicate modification on an internal
guanosine N-2, rather than a ribose hydroxyl. Product mass suggests formation of
a GDP(S) adduct along with a second thiophosphorylation, implying that the
ribozyme catalyzes both phosphoryl and nucleotidyl transfers. This is further
supported by transfer of radiolabels into product from both ? and ? phosphates of
donor molecules. Furthermore, periodate reactivity of the final product signifies
acquisition of a ribose sugar with an intact 2?-3? vicinal diol. Neither
nucleobase modification nor nucleotidyl transfer has previously been reported for
a kinase ribozyme, making this a first-in-class ribozyme. Base-modifying
ribozymes may have played important roles in early RNA world evolution by
enhancing nucleic acid functions.
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