Nucleic Acids Research, Vol 25, Issue 21 4301-4306, Copyright © 1997 by Oxford University Press
S Zhang, M Stancek and LA Isaksson
A cis -cleaving hammerhead ribozyme (Rz) expression system (3A'-Rz) in
Escherichia coli has been constructed that can be used to study the
involvement of factors that affect ribozyme cleavage in vivo . The ribozyme
sequence is placed in the coding region of 3A' mRNA, which is expressed
from a semi-synthetic translation assay gene. The size and the 5'-end
sequences of the 3' cleavage fragments were determined and the efficiencies
of different Rz variants were measured by quantitative primer extension. It
is shown that one of the semi-active constructs (3A'-RzIII) can be used as
an indicator for ribosomes that read through or terminate at a stop codon
upstream of the Rz hammerhead sequence in the mRNA. Readthrough of the stop
codon in an uncleaved mRNA gives a full length 3A' protein. Termination at
the stop codon upstream of the ribozyme sequence gives a shortened
termination product. However, the mRNA fragment that should arise as a
result of the auto-cleavage does not give rise to any detectable
corresponding truncated protein. Besides studies on translating ribosomes,
the 3A'-Rz system can be used to isolate mutant strains that are changed in
ribozyme activity either from internal base alterations, or changed
interacting host factors.
ARTICLES
The efficiency of a cis-cleaving ribozyme in an mRNA coding region is influenced by the translating ribosome in vivo
Department of Microbiology, Stockholm University, S-106 91 Stockholm, Sweden.
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