All mitochondrial tRNAs of the kinetoplastid protozoan
Leishmania tarentolae are encoded in the nucleus and
are imported from the cytosol into the mitochondrion. We previously
reported the partitioning of five tRNAs and found that all were
shared between the two compartments to different extents. To
increase our knowledge of the tRNAs of this organism, and to
attempt to understand the signals involved in their subcellular
localization, a method to RT-PCR amplify new tRNAs was developed.
Various tRNAs were 3′ polyadenylated and reverse transcribed
with a sequence-tagged primer. The cDNA was tagged by ligation
to an anchor oligonucleotide, and the resulting double-tagged
cDNA was amplified by PCR. Four new tRNAs were obtained, bringing
to 20 the total number of L. tarentolae tRNAs identified
to date. The subcellular localization of 17 tRNAs was
quantitatively analyzed by two-dimensional gel electrophoresis
and northern hybridization. In general, the previously suggested
operational classification of tRNAs into three groups (mainly
cytosolic, mainly mitochondrial, and shared between the two
compartments) is still valid, but the relative abundance of
each tRNA in the cytosol or mitochondrion varied greatly as
did the level of expression.