PMID:7748952

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Citation

Tsui, HC and Winkler, ME (1994) Transcriptional patterns of the mutL-miaA superoperon of Escherichia coli K-12 suggest a model for posttranscriptional regulation.Biochimie 76:1168-77

Abstract

The complex amiB-mutL-miaA-hfq-hflX-hflK-hflC superoperon of E coli contains important genes for several fundamental cellular processes, including cell-wall hydrolysis (amiB), DNA repair (mutL), tRNA modification (miaA) and proteolysis (hflX-hflK-hflC). We report here the transcriptional pattern and possible posttranscriptional regulation of mutL, miaA and hfq genes of this superoperon. RNase protection analysis of mRNA transcribed from the bacterial chromosome demonstrated that there is co-transcription of mutL and miaA. In addition, two internal promoters, PmiaA and P1hfq were identified and mapped to 201 and 837 nucleotides upstream from the respective translation start sites. PmiaA contains poor matches to the -10 and -35 regions of the sigma-70 RNA polymerase consensus sequences, but it contains multiple potential Fis-binding sites and an upstream AT-rich region with poly(A) sequences. The basic arrangement of Fis-binding sites followed by an AT rich region is shared with promoters for rRNA operons and some of the tRNA and tRNA modification genes. As part of an initial study of mutL and miaA regulation, we measured transcript amounts in isogenic rne, rnc and rne rnc double mutants which are deficient in RNase E, RNase III or both. The amounts of steady state level mutL-miaA cotranscript, PmiaA transcript and P1hfq transcript increased eight-, nine- and three-fold respectively in an rne3071 mutant when compared to the rne+ parent. In contrast, amounts of the three transcripts were the same in an rnc105 mutant and its rnc+ parent. These results indicate that mutL, miaA, and hfq expression could be regulated by multiple mechanisms, including degree of cotranscription from upstream genes, modulation of internal promoter strength, and by RNase E activity. A model is presented for RNase E-mediated posttranscriptional regulation that may coordinate mutL expression with replication and miaA with tRNA amounts under different growth conditions, especially during nutrient upshifts.

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PubMed

Keywords

Amino Acid Sequence; Base Sequence; Cell Division; Codon; Escherichia coli; Gene Expression Regulation, Bacterial; Genes, Bacterial; Molecular Sequence Data; Operon; Promoter Regions, Genetic; Sequence Homology, Nucleic Acid; Transcription, Genetic

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Materials and Methods Used

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Phenotype Annotations

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Phenotype of Taxon Information Genotype Information (if known) Condition Information OMP ID OMP Term Name ECO ID ECO Term Name Notes Status

a mutation or genetic difference within a strain

  • Taxon: Escherichia coli
  • Strain: K-12
  • Substrain: N3431
  • NCBI Taxon ID: 83333
  • Genotype of Reference Strain: rne
  • Genotype of Experimental Strain : rne3071
  • Reference Condition:
OMP:0000267

increased gene expression

This temperature sensitive mutation up regulates mutL-miaA which are co transcribed, and up regulates transcription of promoters Pmia and P1hfq by a factor of 3, 7 and 8 fold. Table 2.

a mutation or genetic difference within a strain

  • Taxon: Escherichia coli
  • Strain: K-12
  • Substrain: TX2568 (Cmr) & TX2569 (Kmr)
  • NCBI Taxon ID: 83333
  • Genotype of Reference Strain: mutL
  • Genotype of Experimental Strain : mutL:omega(Kmr OR Cmr);BsaAI
  • Reference Condition:
OMP:0000253

gene expression phenotype

The polar omega cassettes blocked mutL-miaA transcription and caused the full-lengthened protected species to disappear, Fig. 2 lanes 3 and 4.


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