Transcription of the S10 ribosomal protein operon is regulated by an attenuator in the leader.

Previous studies have shown that ribosomal protein L4 specifically inhibits the expression of its own operon, the 11-gene S10 operon. To elucidate the mechanism for this regulation, we have examined the effect of protein L4 on transcription of the S10 operon. Hybridization and gel electrophoresis studies indicate that in the presence of excess L4 only RNA molecules about 140 bases long are transcribed from the S10 operon. These short RNA molecules contain the leader, but not structural gene, sequences. Our results suggest that protein L4 stimulates premature termination (attenuation) of transcription about 30 bases upstream from the start of the first structural gene of the S10 operon. The attenuation appears to be independent of the regulation of translation of the operon. We suggest that attenuation of transcription plays a primary role in the autogenous regulation of the S10 operon.