A transcription stimulatory factor binds to the upstream region of Xenopus 5 S RNA and tRNA genes.

Upstream sequence elements modulate transcription efficiency and competition strength of eucaryotic 5 S rRNA and tRNA genes transcribed by RNA polymerase III. We report on the chromatographic separation and functional characterization of at least two components involved in this process: one has a DNA binding activity and interacts with the immediate upstream region of Xenopus tRNA and 5 S rRNA genes, and a second component, which by itself does not interact with the upstream region of these genes, is required together with the DNA binding activity for transcription stimulation in vitro.