An Lrp-like protein of the hyperthermophilic archaeon Sulfolobus solfataricus which binds to its own promoter

Regulation of gene expression in the domain Archaea, and specifically hyper thermophiles, has been poorly investigated so far. Biochemical experiments and genome sequencing have shown that, despite the prokaryotic cell and gen ome organization, basal transcriptional elements of members of the domain A rchaea (i.e., TATA box-like sequences, RNA polymerase, and transcription fa ctors TBP, TFIIB, and TFIIS) are of the eukaryotic type. However, open read ing frames potentially coding for bacterium-type transcription regulation f actors have been recognized in different archaeal strains. This finding rai ses the question of how bacterial and eukaryotic elements interact in regul ating gene expression in Archaea. We have identified a gene coding for a ba cterium-type transcription factor in the hyperthermophilic archaeon Sulfolo bus solfataricus. The protein, named Lrs14, contains a potential helix-turn -helix motif and is related to the Lrp-AsnC family of regulators of gene ex pression in the class Bacteria. We show that Lrs14, expressed in Escherichi a coli, is a highly thermostable DNA-binding protein. Bandshift and DNase I footprint analyses show that Lrs14 specifically binds to multiple sequence s in its own promoter and that the region of binding overlaps the TATA box, suggesting that, like the E. coli Lrp, Lrs14 is autoregulated. We also sho w that the lrs14 transcript is accumulated in the late growth stages of S. solfataricus.