In vitro transcription of a silkworm 5S RNA gene requires an upstream signal

The RNA polymerase III transcription complex from Bombyx mori silkworms, in contrast to that from Xenopus frogs, requires a signal that is upstream from the transcription initiation site. We have found that part of the normal 5' flanking sequence is essential for transcription of Bombyx 5S RNA genes by homologous cell-free extracts. The critical region is structurally similar to the upstream signal that directs Bombyx tRNA gene transcription. The association of such a control element with two classes of polymerase III templates argues that it acts through a general component of the Bombyx transcription apparatus.