Mutations in Box B of the promoter of a eucaryotic tRNAPro gene affect rate of transcription, processing, and stability of the transcripts.

We have constructed a series of single and double base-pair-substitution mutants in and around the second component (Box B) of the promoter of a tRNAPro gene from C. elegans. Their analysis in in vivo and in vitro transcriptional systems establishes the importance of single nucleotides in the promotion of transcription. Most mutants in the region coding for the TpsiCG stem-loop show a reduced gene expression associated with lack of processing of the primary transcriptional products; in the oocytes these are rapidly degraded, with a half-life considerably shorter than that of wild-type tRNA molecules. In contrast, mutations in the DNA region coding for the anticodon stem-loop do not alter the efficiency of transcription or the processing of the transcripts.