Processing of mammalian tRNA transcripts in vitro: different pre-tRNAs are processed along alternative pathways that contain a common rale-limiting step

摘要

We have analyzed the pathways and kinetics of processing of mouse tRNA gene transcripts in vitro. Different transcripts are processed along two alternative pathways. The 3′ trailer sequence of the tRNAHis primary transcript is excised before the 5′ leader sequence. In contrast, for the tRNAGly primary transcript, the 5′ leader sequence is excised before the 3′ trailer sequence, as has been found for other monomeric eukaryotic tRNA gene transcripts. Computerized analysis of the kinetics of processing indicates that tRNAAsp, tRNAGly, tRNAGlu and tRNA Histranscripts are processed in a substrate concentration-dependent manner and also reveals the existence of a common rate-limiting step, the rate constant of which is equivalent for three of the four transcripts tested. The processing of one pre-tRNA transcript can be competitively inhibited by addition of another pre-tRNA transcript to the processing reaction. The common rate-limiting step is associated with the conversion of the primary transcript to an intermediate and is independent of sequence and the particular processing pathway of the transcript.