Nucleic Acids Research, Vol 25, Issue 9 1825-1829, Copyright © 1997 by Oxford University Press
M Hetzer, RJ Schweyen and MW Mueller
The excised group II intron bI1 from Saccharomyces cerevisiae can act as a
ribozyme catalysing various chemical reactions with different substrate
RNAs in vitro . Recently, we have described an editing-like RNA
polymerization reaction catalysed by the bI1 intron lariat that proceeds in
the 3'-->5'direction. Here we show that the bI1 lariat RNA can also
catalyse successive deoxyribonucleotide polymerization reactions on
exogenous substrate molecules. The basic mechanism of the reaction involved
interacting cycles between an alternative version of partial reverse
splicing (lariat charging) and canonical forward splicing (lariat
discharging by exon ligation). With an overall chain growth in the
3'-->5' direction, the 5' exon RNAs (IBS1dN) were elongated by
successive insertion of deoxyribonucleotides derived from single
deoxyribonucleotide substitutions (dA, dG, dC or dT). All four
deoxyribonucleotides were used as substrates, although with different
efficiencies. Our findings extend the catalytic repertoire of group II
intron RNAs not only by a novel DNA polymerization activity, but also by a
DNA-DNA ligation capacity, supporting the idea that ribozymes might have
been part of the first primordial polymerization machinery for both RNA and
DNA.
ARTICLES
DNA polymerization catalysed by a group II intron RNA in vitro
Vienna Biocenter, Institute of Microbiology and Genetics, University of Vienna, Dr Bohr-Gasse 9, A-1030 Vienna, Austria.
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