The specificity and efficiency of manganese ion-induced RNA hydrolysis
was studied with several tRNA molecules, In case of yeast tRNA(Phe),
the main cleavage occurs at p16 and minor cuts at p17-18, p20-21, p34
and p36-37. The major Mn(Il)-induced cut in yeast elongator tRNA(Met)
is also located in the D-loop at p16 and it is stronger than that obse
rved in tRNA(Phe). In initiator tRNA(Met) from yeast two strong Mn(II)
cleavages of equal intensity occur at p16 and p17. This is in contras
t with single, much weaker cuts induced in the D-loop of that tRNA by
Mg(II), Eu(III) and Pb(II) ions. Interestingly in case of yeast tRNA(G
lu) the main cleavage caused by Mn(II), Mg(II) and Pb(II) ions occurs
in the anticodon loop. The involvement of hypermodified base mnm(5)S(2
)U in this cleavage was ruled out based on results obtained,vith in vi
tro transcript of yeast tRNA(Glu) anticodon arm, Mutation of a single
base A37G in the anticodon loop of the transcript drastically reduced
the specificity of Mn(II)-induced hydrolysis.