In vitro transcription of RU, a middle repetitive element of the rat genome.

Repetitive DNA sequences have been found within as well as adjacent to the rat growth hormone (rGH) gene (1,2). In vitro transcription of the rGH gene yields transcripts predominantly from a tandemly duplicated repeat (RU) in the second intron of the gene. The relative alpha-amanitin sensitivity of this transcription indicates that it is carried out by RNA polymerase III. Transcription initiates within a 5' flanking 15 base-pair repeat, and terminates within a stretch of A residues at the end of each repeat, a termination site that is notably unlike most of those used by polymerase III. Approximately 75% of the transcripts stop at the end of the first repeat; the remainder "read-through" to a homologous termination region at the end of the second repeat.