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Abstract Bacteria contain conserved mechanisms to control the intracellular levels of metal ions. Metalloregulatory transcription factors bind metal cations and play a central role in regulating gene expression of metal transporters. Often, these transcription factors regulate transcription by binding to a specific DNA sequence in the promoter region of target genes. Understanding the preferred DNA‐binding sequence for transcriptional regulators can help uncover novel gene targets and provide insight into the biological role of the transcription factor in the host organism. Here, we identify consensus DNA‐binding sequences and subsequent transcription regulatory networks for two metalloregulators from the ferric uptake regulator (FUR) and diphtheria toxin repressor (DtxR) superfamilies inThermus thermophilusHB8. By homology search, we classify the DtxR homolog as a manganese‐specific, MntR (TtMntR), and the FUR homolog as a peroxide‐sensing, PerR (TtPerR). Both transcription factors repress separate ZIP transporter genes in vivo, andTtPerR acts as a bifunctional transcription regulator by activating the expression of ferric and hemin transport systems. We showTtPerR andTtMntR bind DNA in the presence of manganese in vitro and in vivo; however,TtPerR is unable to bind DNA in the presence of iron, likely due to iron‐mediated histidine oxidation. Unlike canonical PerR homologs,TtPerR does not appear to contribute to peroxide detoxification. Instead, theTtPerR regulon and DNA binding sequence are more reminiscent of Fur or Mur homologs. Collectively, these results highlight the similarities and differences between two metalloregulatory superfamilies and underscore the interplay of manganese and iron in transcription factor regulation.
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Regulation of late‐acting operons by three transcription factors and a CRISPR‐Cas component during Myxococcus xanthus development
Abstract Upon starvation, rod‐shapedMyxococcus xanthusbacteria form mounds and then differentiate into round, stress‐resistant spores. Little is known about the regulation of late‐acting operons important for spore formation. C‐signaling has been proposed to activate FruA, which binds DNA cooperatively with MrpC to stimulate transcription of developmental genes. We report that this model can explain regulation of thefadIJoperon involved in spore metabolism, but not that of the spore coat biogenesis operonsexoA‐I,exoL‐P, andnfsA‐H. Rather, a mutation infruAincreased the transcript levels from these operons early in development, suggesting negative regulation by FruA, and a mutation inmrpCaffected transcript levels from each operon differently. FruA bound to all four promoter regions in vitro, but strikingly each promoter region was unique in terms of whether or not MrpC and/or the DNA‐binding domain of Nla6 bound, and in terms of cooperative binding. Furthermore, the DevI component of a CRISPR‐Cas system is a negative regulator of all four operons, based on transcript measurements. Our results demonstrate complex regulation of sporulation genes by three transcription factors and a CRISPR‐Cas component, which we propose produces spores suited to withstand starvation and environmental insults.
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- Award ID(s):
- 1951025
- PAR ID:
- 10507400
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Molecular Microbiology
- Volume:
- 121
- Issue:
- 5
- ISSN:
- 0950-382X
- Format(s):
- Medium: X Size: p. 1002-1020
- Size(s):
- p. 1002-1020
- Sponsoring Org:
- National Science Foundation
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