The TATA motif, the CAA motif and the poly(T) transcription termination motif are all important for transcription re-initiation on plant tRNA genes

The effect of alteration of 5' and 3' flanking sequences on the transcripti on of plant tRNA genes was analysed using an RNA polymerase III-dependent i n vitro transcription system derived from nuclei of cultured tobacco cells. A TATA-like sequence and the CAA motif frequently observed upstream of pla nt tRNA genes, and the poly(T) stretch usually present downstream, were sho wn to be necessary for efficient re-initiation of transcription. The CAA mo tif was shown to be a transcription initiation site. Introduction of the CA A and TATA-like motifs into a gene naturally lacking them greatly enhanced transcription by promoting efficient re-initiation.