Transcriptional regulation of the gene encoding an alcohol dehydrogenase in the archaeon Sulfolobus solfataricus involves multiple factors and control elements

The understanding of basic processes in the kingdom Archaea has been greatly favoured by the completion of several genome sequencing projects like S. solfataricus, and the recent development of the post genomic era which helps in translating the sequence database into a functional one. But, despite their simplicity, there is still a lot to know about them. This lack of understanding encompasses the areas of the growth, metabolism and physiology of this group of organisms and is a reflection of the dearth of experimental approaches applicable to these microrganisms. By using genetic approaches, the analysis can encompass interesting pathways, their metabolic regulatory and structural components, and the study of gene function; this can help in revealing novel aspects of archaeal biology that can not be addressed in alternative studies. In order to give insight into transcriptional regulation, we analysed the regulation of the alcohol dehydrogenase gene (adh) in the Archaeon Sulfolobus solfataricus and demonstrated that the gene is finely regulated at transcriptional level in response to the benzaldehyde, substrate of the enzyme. In this model system we evaluated the activity of putative transcriptional regulators and the role of the region upstream of the gene; this purpose was achieved by identifying on one hand, the cis-acting responsive sequences in the promoter region, and on the other the trans-acting factor(s) responsible for the benzaldehyde-mediated induction. The identification of the interacting factor(s) revealed that more than one protein binds to this region. Understanding the nature of protein-protein and DNA-protein interaction could allow to desume a model able to clarify the molecular basis of such a fine modulation of gene expression in S. solfataricus. The activity of the adh promoter has also been analysed in an in vivo reporter system by fusion to the alcohol dehydrogenase gene from the moderate thermophile Bacillus stearothermophilus and cloning in the S.solfataricus/E.coli shuttle vector pEXSs. This system seems to be powerful for in vivo characterisation of transcriptional activity.