The mechanism of preferential synthesis of poly[r(purine)] in the transcription of poly[d(purine)] . poly[d(pyrimidine)] by T. thermophilus RNA polymerase.

The mechanism of preferential transcription on poly[d(purine)] . poly[d(pyrimidine)] was investigated using RNA polymerase of T. thermophilus HB8. Though the machinery for initiation is lacking, the core enzyme has the latent ability to synthesize poly[r(pyrimidine)] as well as poly[r(purine)]. The holoenzyme can synthesize poly[r(purine)] in the usual manner. Poly[r(pyrimidine)] synthesis by the holoenzyme is, however, forbidden. These results suggest that the sigma factor plays a crucial role in this preferential transcription, and that this preferential transcription may be useful as a model for the sense strand recognition. Various results led us to the hypothesis that the high affinity site for the poly[d(pyrimidine)] strands on the enzyme plays a very important role.