Two control regions for eukaryotic tRNA gene transcription.

Abstract
Two Drosophila tRNALys genes with identical coding sequences transcribe with very different efficiencies in nuclear extracts from Xenopus oocytes. The use of recombinant plasmids in which the 5''-flanking sequences of these genes were either switched or replaced by defined [Escherichia coli] pBR322 sequences revealed 2 control regions for tRNA gene transcription. An internal control region comprising the mature tRNA coding sequence (and possibly its 3''-flanking sequences) is sufficient for transcription initiation, and an external control region comprising the 5''-flanking sequences represses this transcription. All transcripts have short leader sequences. Altered precursor tRNA transcribed from truncated tRNALys genes (missing a single base pair in the acceptor stem) are not processed well in vitro.