The 5- flanking sequences of Drosophila tRNAArg genes control their in vitro transcription in a Drosophila cell extract.

The transcription efficiencies of four Drosophila tRNAArg genes located in a tRNA gene cluster at region 42A on chromosome 2, and containing identical coding sequences, were studied in Drosophila Kc cell extracts. Transcription is modulated by the 5' flanking sequences; efficient transcription is dependent on the presence of an optimal 5' flanking sequence. One of the genes, p17D Arg, is not transcribed in the homologous extract but does compete with the other genes for transcription factors. Deletion of a specific sequence from the 5' flank of the gene of p17D Arg leads to an increase in transcription efficiency. All tRNAArg genes are efficiently transcribed in extracts from HeLa cells. However, introduction of small amounts of Drosophila extract reduces the efficiency of transcription in HeLa extracts. This is due to incompatibility between transcriptional components of the two extracts.