A yeast tRNAArggene can act as promoter for a 5′ flank deficient, non-transcribable tRNASUP6gene to produce biologically active suppressor tRNA

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Abstract
In S. cerevisiae most tRNA genes are located and expressed as single entities. The tDNAArg-tDNAAsp pair, however, is transcribed into a dimeric precursor before being processed into two nature tRNA species. The second gene of this pair, tDNAAsp, is totally dependent on the first gene, tDNAArg, and its promoter components, for homologous in vitro transcription. The second gene in the pair is now replaced by the ochre suppressor tDNASUP6-o, which, by itself, cannot be transcribed because of a nonfucntional 5′ flanking region. The tDNAArg - tDNASUP6-o was transcribed into a dimeric precursor which was processed to nature tRNA molecules as judged in vitro by electroforetic separation, and in vivo by their ability to suppress ochre but not amber yeast mutations. Mutations in the internal promoter of the first gene decreased transcription, both in vitro and in vivo, of the second - tRNASUP6-o - gene. Thus tDNAArg with its 5′ flanking region can act as an external promoter for other RNA polymerase III-read genes that are by themselves inactive due to impaired promoter/modulator regions.