Transcriptional Regulation of Carbon Utilization in the Hyperthermophilic Archaeon Sulfolobus Solfataricus

[9604000 . Blum]本研究旨在确定克服极端温度下基因表达调节的固有生物物理限制的进化机制，并进一步阐明古细菌的进化地位。基于rDNA序列比较的系统发育研究表明，古细菌与真核生物和真细菌都有远亲关系。尽管古细菌在系统发育上不同于真核生物，但它们的转录成分却表现出显著的相似性。然而，尚不清楚这种相似性是否延伸到DNA序列和调节转录的因子。最近发现的好氧、超嗜热的硫酸根分解代谢抑制（CR）反应将被用作古细菌基因调控研究的模型系统。该系统的一个组成部分称为CR-I，由碳利用酶水平的变化及其各自的转录物在单一碳和能源层次上的生长引起。cr - 1调节malA（麦芽糖酶）、malE（外糖酶）和多顺反电子malL簇的表达。由于基因组分析表明这些靶基因中的一些在物理上是不相连的，因此CR-I使用一个全局调控机制来控制基因表达。此外，cr - 1上调malA和malE，下调malL。本研究将确定CR-I调控是否发生在转录起始水平，并将确定CR-I控制不良基因表达所需的顺式和反式因子。这项研究的结果将阐明好氧超嗜热古菌如何调节基因表达以选择性消耗碳。虽然在古细菌的两个分支——Euryarchaeota和Crenarchaeota中都存在超嗜热菌，但它们的dna异乎寻常地根深蒂固，这表明它们是地球上最早出现的生物之一。因此，这项研究可能为基因表达的进化起源提供额外的见解。基于核糖体DNA （rDNA）序列比较的系统发育研究发现了一种被称为古细菌的独特生物群，它与真核生物和真细菌都有远亲关系。尽管古细菌在系统发育上不同于真核生物，但它们的转录成分却表现出显著的相似性。然而，尚不清楚这种相似性是否延伸到DNA序列和调节转录的因子。超嗜热菌硫酸根（Sulfulobus solfataricus）将作为古细菌基因调控研究的模型系统。预期的结果将阐明有氧嗜热古菌如何在极端温度下调节基因表达，并将为古菌嗜热代谢的基本方面和基因表达的进化起源提供见解。

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.