Transcriptional Regulation of Carbon Utilization in the Hyperthermophilic Archaeon Sulfolobus Solfataricus

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9604000 Blum This research seeks to identify mechanisms which have evolved to overcome the inherent biophysical constraints imposed on the regulation of gene expression at extreme temperatures, as well as further clarify the evolutionary position of the Archaea. Phylogenetic studies based on comparison of rDNA sequences have shown that the Archaea are distantly related to both Eubactria and Eukaryotes. Although Archaea are phylogentically distinct from Eukaryotes, their transcriptional components exhibit remarkable similarity. However, it is not know whether this similarity extends to DNA sequences and factors that regulate transcription. The recently discovered Catabolite Repression (CR) response in the aerobic, hyperthermophile Sulfulobus solfataricus will be used as a model system to study gene regulation in archaeons. One component of this system termed CR-I consists of variations in levels of carbon utilization enzymes and their respective transcripts elicited by growth on a hierarchy of sole carbon and energy sources. CR-I regulates expression of malA (maltase), malE (exogluconase) and the polycistronic malL cluster. Since genomic analysis indicates that several of these target genes are physically unlinked, CR-I uses a global regulatory mechanism to control gene expression. Moreover, CR-I appears to up regulate malA and malE while down regulating malL. This research will determine if CR-I regulation occurs at the level of transcription initiation and will identify the cis and trans-acting factors necessary for CR-I control of mal gene expression. The results of this research will clarify how aerobic hyperthermophilic Archaea regulate gene expression for the selective consumption of carbon. While hyperthermophiles are are present in both archaeal sub-divisions, the Euryarchaeota and the Crenarchaeota, their rDNAs are unusually deeply rooted suggesting that they were among the first organisms to appear on earth. This research therefore may provide additional insight into the ev olutionary origin of gene expression. Phylogenetic studies based on comparison of ribosomal DNA (rDNA) sequences have led to the discovery of a distinct group of organisms termed the Archaea which are distantly related to both Eubactria and Eukaryotes. Although Archaea are phylogentically distinct from Eukaryotes, their transcriptional components exhibit remarkable similarity. However, it is not know whether this similarity extends to DNA sequences and factors that regulate transcription. The hyperthermophile Sulfulobus solfataricus will be used as a model system to study gene regulation in archaeons. The anticipated results will clarify how aerobic hyperthermophilic Archaea regulate gene expression at extreme tempertures, and will provide insight into basic aspects of archaeal hyperthermophilic metabolism and the evolutionary origin of gene expression.