Investigation of Streptomyces promoters

Doctoral Thesis


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University of Cape Town

[The work described here had multiple aims: to create a promoter probe that was suitable for the isolation of developmentally regulated Strepcomyces promoters, to isolate such promoters, to develop a computer assisted analysis system whereby potential promoter sequences could be determined and to use this in the analysis of the cloned promoters. Initially the suitability of the Streptomyces antibioticus me1C operon for use as a reporter system in Streptomyces was investigated. It was established that late-expressed promoters could be identified and that it was possible to use the me1C2 gene alone for this purpose. However, it was shown that the use of both me1C1 and me1C2 resulted in a more sensitive reporter system. High copy number promoter probe vectors were constructed and tested. A low copy number promoter probe (which used the Streptomyces penemefaciens pSPN1 origin of replication) was also constructed. The characteristics (copy number, stability and mobility) of the probe were established. The conditions in which sporulation was induced by phosphate limitation were identified. Under such conditions late expressing, phosphate dependent promoters were isolated, using the promoter probes previously developed. The expression of these promoters was tested in Streptomyces coelicolor bldA mutants, and the bldA dependent promoters identified. These were sequenced. Computer assisted analysis of DNA sequence bias was conducted, with the intention of using bias patterns to identify potential regulatory regions. The initial approach of using the sequence bias of protein coding regions (based on the premise that regulatory sites are likely to be under represented in these regions) was unsuccessful. Further analysis in which the positional preference of sequences that were over represented in regulatory regions was conducted. Based on this the known promoters of Streptomyces were partially classified. The sequence bias of protein coding DNA regions was used to develop a novel method to identify the protein coding regions of Streptomyces DNA. The computer programs were then used to identify protein coding and potential regulatory regions.

Bibliography: leaves 221-[234].