Effects of temperature and single-stranded DNA on the interaction of an RNA polymerase III transcription factor with a tRNA gene.

It has previously been shown that a yeast RNA polymerase III transcription factor binds stably to tRNA genes. The principal protein-DNA contacts have now been mapped, by dimethylsulfate footprinting, to the vicinity of the A and B block promoter regions of the S. cerevisiae tRNALeu3 gene. Single-stranded DNA preferentially interferes with the binding of the transcription factor to one of the promoter regions. The effect of temperature on the formation of the transcription factor-DNA complex has been examined: the complex has the kind of "opening" property that has been previously associated with prokaryotic RNA polymerase-promoter complexes, with stability increasing as the temperature is raised.