The RNase E family is renowned for being central to
the processing and decay of all types of RNA in
many species of bacteria, as well as providing the
first examples of endonucleases that can recognize
50
-monophosphorylated ends thereby increasing
the efficiency of cleavage. However, there is
increasing evidence that some transcripts can be
cleaved efficiently by Escherichia coli RNase E via
direct entry, i.e. in the absence of the recognition of
a 50
-monophosphorylated end. Here, we provide
biochemical evidence that direct entry is central to
the processing of transfer RNA (tRNA) in E. coli, one
of the core functions of RNase E, and show that it is
mediated by specific unpaired regions that are
adjacent, but not contiguous to segments cleaved
by RNase E. In addition, we find that direct entry at a
site on the 50 side of a tRNA precursor triggers a
series of 50
-monophosphate-dependent cleavages.
Consistent with a major role for direct entry
in tRNA processing, we provide additional evidence
that a 50
-monophosphate is not required to
activate the catalysis step in cleavage. Other
examples of tRNA precursors processed via direct
entry are also provided. Thus, it appears increasingly
that direct entry by RNase E has a major role
in bacterial RNA metabolism.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)