A single promoter designated P<i><sub>mra</sub></i>, was previously identified upstream of the <i>mra</i> region. P<i><sub>mra</sub></i> was reported to be essential for expression of the first nine genes of the <i>mra</i> region and may contribute to expression <i>fts</i>Q, A, and Z at the distal end of this gene cluster. This study investigates potential mechanisms of transcriptional regulation at P<i><sub>mra</sub></i>, in addition to the regulation of two newly identified promoters (P<i><sub>mra</sub></i>2 and P<i><sub>mra</sub></i>3) in the <i>fru</i>R-<i>yab</i>B intergenic region. Using <i>lacZ</i> reporter strains we determined that transcription from the P<i><sub>mra</sub></i> promoters was inversely related to growth rate. Promoters P<i><sub>mra</sub></i>1 and P<i><sub>mra</sub></i>3 were the major contributors to the transcription of early genes in the <i>mra</i> region. Transcripts originating from these promoters were detected by RT-PCR to span at least as far as <i>fts</i>L. The transcriptional regulator FIS was shown to bind several sites in the intergenic region, including sequences within the promoter regions of both P<i><sub>mra</sub></i>2 and P<i><sub>mra</sub></i>3. FIS caused a 3-fold repression of P<i><sub>mra</sub></i>2 but had little effect on the transcriptional activity of P<i><sub>mra</sub></i>3. It was noted that presence of the entire intergenic region caused a 4-fold repression of P<i><sub>mra</sub></i>3, indicating that transcriptional regulators interact with the DNA upstream of this promoter. The 50S subunit ribosomal protein L3 was shown to bind upstream of P<i><sub>mra</sub></i>3 . P<i><sub>mra</sub></i>3 was also shown to be repressed by the cellular alarmone ppGpp which is produced as part of the stringent response and during slow growth or carbon starvation. It was not possible to delete P<i><sub>mra</sub></i>3 from the chromosome suggesting that it may be essential for cell viability.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:650017 |
| Date | January 2006 |
| Creators | Emmins, Robyn |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14793 |
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