RNase P as hyperprocessing enzyme: a model for formation of a biologically functional tRNA fragment.

Hyperprocessing is defined as a further processing of mature RNA that produces another functional RNA. Hyperprocessing occurs in Drosophila cells. In the transposon copia-related retrovirus-like particles of Drosophila, a 39-nucleotide-long fragment from the 5'region of Drosophila initiator methionine tRNA is used as the primer for copia minus-strand reverse transcription. This primer tRNA fragment is thought to be produced by cleavage within the mature tRNA sequence. We found that the catalytic RNA subunit of RNase P catalyzes this hyperprocessing in vitro and that this cleavage is dependent of the occurrence of an altered conformation of the tRNA substrate. In this review, I will summarize our work from the finding of the functional RNA fragment to the finding of a dynamic tRNA structure.