Convergent transcription of the E.coli hisG gene cloned in B. subtilis stops in the vicinity of the attenuator

A 5300-bp DNA segment containing the promoter, the attenuator and the first gene (hisG) of the Escherichia coli his operon has been inserted into an interspecific E. coli-Bacillus subtilis plasmid vector, pHV14. The resulting plasmid pPV48 restores the His+ phenotype to an E. coli hisG mutant, but fails to do so to a corresponding B. subtilis mutant. Experiments aimed at localizing the block to this heterologous expression in B. subtilis have shown that the enzymatic activity of the hisG+ gene product is neither detectable nor inhibited in crude extracts of B. subtilis cells harboring pPV48. Furthermore, electron microscopic, Southern blot and S1 mapping analysis of the transcripts produced in vitro and in vivo by B. subtilis RNA polymerase indicate that the hisG+ region is transcribed, but that the transcripts initiate at sites different from the his promoter, converge towards, and terminate in the vicinity of the attenuator.