A Novel Archaeal Transcriptional Regulator of Heat Shock Response
Journal of Biological Chemistry
Archaea have a eukaryotic type of transcriptional machinery containing homologues of the transcription factors TATA-binding protein (TBP) and TFIIB (TFB) and a pol II type of RNA polymerase, whereas transcriptional regulators identified in archaeal genomes have bacterial counterparts. We describe here a novel regulator of heat shock response, Phr, from the hyperthermophilic archaeon Pyrococcus furiosus that is conserved among Euryarchaeota. The protein specifically inhibited cellfree
... cellfree transcription of its own gene and from promoters of a small heat shock protein, Hsp20, and of an AAA ؉ ATPase. Inhibition of transcription was brought about by abrogating RNA polymerase recruitment to the TBP/ TFB promoter complex. Phr bound to a 29-bp DNA sequence overlapping the transcription start site. Three sequences conserved in the binding sites of Phr, TTTA at ؊10, TGGTAA at the transcription start site, and AAAA at position ؉10, were required for Phr binding and are proposed as consensus regulatory sequences of Pyrococcus heat shock promoters. Shifting the growth temperature from 95 to 103°C caused a dramatic increase of mRNA levels for the aaa ؉ atpase and phr genes, but expression of the Phr protein was only weakly stimulated. Our findings suggest that heat shock response in Archaea is negatively regulated by a mechanism involving binding of Phr to conserved sequences.