A tRNALeu-like sequence located immediately upstream of an Arabidopsis clock-regulated gene is transcriptionally active: efficient transcription by an RNA polymerase III-dependent in vitro transcription system

Abstract

A tRNALeu-like sequence is located within a probable enhancer region of the RNA polymerase II-dependent gene encoding an RNA-binding protein, Atgrp7, in Arabidopsis (Mol. Gen. Genet. 261 (1999) 811). To examine whether this sequence is transcribed, we used our in vitro transcription system from tobacco cell nuclei. In vitro assays demonstrated that this tRNA-like sequence is transcribed by RNA polymerase III and its transcript is processed into tRNA-size molecules. Transcription starts at the CAA motif, a transcription initiation site for many plant tRNA genes. Mutation analyses indicated that transcription of this sequence depends on promoter elements typical for plant tRNA genes. We therefore concluded that this is a transcriptionally active tRNALeu(AAG) gene. Mutation of a basic promoter element of the tRNA gene exerted no influence on the transcription of the downstream protein-coding gene, suggesting that no apparent interference occurs between the two adjacent genes.