Cleavage of tRNA within the mature tRNA sequence by the catalytic RNA of RNase P: implication for the formation of the primer tRNA fragment for reverse transcription in copia retrovirus-like particles.

The retrovirus-like particles of Drosophila are intermediates of retrotransposition of the transposable element copia. In these particles, a 39-nucleotide-long fragment from the 5' region of Drosophila initiator methionine tRNA (tRNA(iMet) is used as the primer for copia minus-strand reverse transcription. To function as primer for this reverse transcription, the Drosophila tRNA(iMet) must be cleaved in vivo at the site between nucleotides 39 and 40. When a synthetic Drosophila tRNA(iMet) precursor was incubated with M1RNA, the catalytic RNA of Escherichia coli RNase P, other cleavages within the mature tRNA sequence were detected in addition to the efficient removal of the 5' leader sequence of this tRNA precursor. One of these cleavage sites is between nucleotides 39 and 40 of Drosophila tRNA(iMet). Based on this result, we propose a model for formation of the primer tRNA fragment for reverse transcription in copia retrovirus-like particles.