''rpoN''

The gene rpoN (RNA polymerase, nitrogen-limitation N) encodes the sigma factor sigma-54 (σ54, sigma N, or RpoN), a protein in Escherichia coli and other species of bacteria. RpoN antagonizes RpoS sigma factors.[1]

Biological role

Originally identified as a regulator of genes involved in nitrogen metabolism and assimilation under nitrogen limiting conditions,[2] E. coli σ54 has since been shown to play important regulatory roles in a variety of other cellular processes. Similarly, σ54 homologues in other species regulate a wide range of processes, including flagellar synthesis and virulence.[3]

Sequence specificity and mechanism of action

σ54 promoter elements consist of conserved nucleotides located at −12 and −24 with respect to the transcription start site.[4] This contrasts with members of the σ70 family, which recognize conserved promoter elements located at roughly −10 and −35 with respect to the transcription start site.[5] Unlike the members of the σ70 family, σ54 proteins have been shown to bind promoter DNA independent of core RNAPin vitro.[6] Another distinguishing characteristic of σ54 proteins is their absolute requirement for activator proteins, known as bacterial enhancer binding proteins (bEBPs), to initiate transcription.[4][7] Thus, both active and inactive forms of RNAP:σ54 are bound at promoters.[8]

The RpoN-regulated promoter elements have the consensus sequence as follows: TTGGCACGGTTTTTGCT.[9]

References

  1. ↑ Dong, T; Yu, R; Schellhorn, H (2011). "Antagonistic regulation of motility and transcriptome expression by RpoN and RpoS in Escherichia coli". Molecular Microbiology. 79 (2): 375–86. doi:10.1111/j.1365-2958.2010.07449.x. PMID 21219458.
  2. ↑ Hunt, TP; Magasanik, B (1985). "Transcription of glnA by purified Escherichia colicomponents: core RNA polymerase and the products of glnF, glnG, and glnL". Proc Natl Acad Sci USA. 82: 8453–8457. doi:10.1073/pnas.82.24.8453. PMC 390934. PMID 2867543.
  3. ↑ Tsang, J; Hoover, TR (2014). "Themes and Variations: Regulation of RpoN-Dependent Flagellar Genes across Diverse Bacterial Species". Scientifica. 2014: 681754. doi:10.1155/2014/681754. PMC 3930126. PMID 24672734.
  4. 1 2 Wigneshweraraj, S; Bose, D; Burrows, PC; Joly, N; Schumacher, J; et al. (2008). "Modus operandi of the bacterial RNA polymerase containing the sigma54 promoter-specificity factor". Mol Microbiol. 38: 538–546. doi:10.1111/j.1365-2958.2008.06181.x.
  5. ↑ Gruber, T; Gross, CA (2003). "Multiple Sigma subunits and the partitioning of bacterial transcription space". Annu Rev Microbiol. 57: 441–466. doi:10.1146/annurev.micro.57.030502.090913. PMID 14527287.
  6. ↑ Buck, M; Cannon, W (1992). "Specific binding of the transcription factor sigma-54 to promoter DNA". Nature. 358: 422–424. doi:10.1038/358422a0. PMID 1641025.
  7. ↑ Shingler, V (2011). "Signal sensory systems that impact σ54-dependent transcription". FEMS Microbiol Rev. 35: 425–440. doi:10.1111/j.1574-6976.2010.00255.x. PMID 21054445.
  8. ↑ Bonocora, RP; Smith, C; Lapierre, P; Wade, JT (2015). "Genome-Scale Mapping of Escherichia coli σ54 Reveals Widespread, Conserved Intragenic Binding". PLoS Genet. 11 (10): e1005552. doi:10.1371/journal.pgen.1005552.
  9. ↑ Leang, C; Krushkal, J; Ueki, T; Puljic, M; Sun, J; Juárez, K; Núñez, C; Reguera, G; DiDonato, R; Postier, B; Adkins, RM; Lovley, DR (2009). "Genome-wide analysis of the RpoN regulon in Geobacter sulfurreducens". BMC Genomics. 10: 331. doi:10.1186/1471-2164-10-331. PMC 2725144. PMID 19624843.


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