The hsp operons are repressed by the hrc37 of the hsp70 operon in Staphylococcus aureus

The heat-shock proteins are coded for the polycistronic operons hsp70 and hsp60 in Staphylococcus aureus. The hsp70 operon is comprised of five genes, hrc37, hsp20, hsp70, hsp40 and orf35, and the hsp60 is comprised of two genes, hsp10 and hsp60. The hsp70 operon transcribed five different sizes of mRNA from three promoters: P1, the most active promoter, transcribed 6.0 and 3.6 kb mRNAs; P2 transcribed a single 1.8 kb mRNA; and P3 transcribed 4.2 and 2.4 kb mRNAs. The hsp60 operon transcribed a single 2.1 kb transcript from only one promoter, P1. Both operons had a common structure of inverted repeat element (CIRCE, Controlling Inverted Repeat of Chaperon Expression) at the promoter region. All of the transcripts were heat (46 C) inducible. One of the unidentified genes, hrc37, was characterized. The disruptant of the hrc37 in the hsp70 operon enhanced the transcription of both operons at 37 C (derepression). Complementation of the disruptant with the cloned hrc37 plasmid recovered the repression of the transcription of both operons at 37 C. The product of hrc37, Hrc37, was found to bind to the CIRCE element. These findings indicated that Hrc37 from the hsp70 operon repressed the transcription of both the hsp70 and hsp60 operons by binding to the CIRCE element located at the promoter region.