A. Tallsjo et al., INTERACTION BETWEEN ESCHERICHIA-COLI RNASE-P RNA AND THE DISCRIMINATOR BASE RESULTS IN SLOW PRODUCT RELEASE, RNA, 2(4), 1996, pp. 299-307
We suggested previously that a purine at the discriminator base positi
on ina tRNA precursor interacts with the well-conserved U294 in M1 RNA
, the catalytic subunit of Escherichia coli RNase P. Here we investiga
ted this interaction and its influence on the kinetics of cleavage as
well as on cleavage site selection. The discriminator base in precurso
rs to tRNA(Tyr)Su3 and tRNA(Phe) was changed from A to C and cleavage
kinetics were studied by wild-type M1 RNA and a mutant M1 RNA carrying
the compensatory substitution of a U to a G at position 294 in M1 RNA
. Our data suggest that the discriminator base interacts with the resi
due at position 294 in M1 RNA. Although product release is a rate-limi
ting step both in the absence and in the presence of this interaction,
its presence results in a significant reduction in the rate of produc
t release. In addition, we studied cleavage site selection on various
tRNA(His) precursor derivatives. These precursors carry a C at the dis
criminator base position. The results showed that the mutant M1 RNA ha
rboring a G at position 294 miscleaved a wild-type tRNA(His) precursor
and a tRNA(His) precursor carrying an inosine at the cleavage site. T
he combined data suggest a functional interaction between the discrimi
nator base and the well-conserved U294 in M1 RNA. This interaction is
suggested to play an important role in determining the rate of product
release during multiple turnover cleavage of tRNA precursors by M1 RN
A as well as in cleavage site selection.