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Antimicrobial Agents and Chemotherapy, August 2007, p. 3040-3041, Vol. 51, No. 8
0066-4804/07/$08.00+0     doi:10.1128/AAC.00594-07

LETTER TO THE EDITOR

Extended –10 Promoter in ISAba-1 Upstream of blaOXA-23 from Acinetobacter baumannii{triangledown}


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Molecular studies showed that carbapenem-resistant Acinetobacter baumannii strains isolated from patients in hospitals in Cape Town contain blaOXA-23 (7). Concordant with the findings of others (4, 11), PCR assays showed that of the 43 strains investigated, blaOXA-23 was consistently associated with ISAba-1. One strain, designated RAM (8), was selected to identify the transcription promoter located upstream of blaOXA-23.

Total RNA was extracted from strain RAM using the hot acid phenol method (1), and primer extension studies were carried out (9). The primer extension products were analyzed in conjunction with products of sequencing reactions performed on the corresponding DNA. The extension product mapped to a T 63 nucleotides upstream of the blaOXA-23 start codon (Fig. 1). The hexamers TTAGAA (–35) and TTATTT (–10) are upstream of this start site. The sequence (TGACA) immediately upstream of the –10 box generates an extended –10 hexamer that shows similarity to sequences recognized by the {sigma}S subunit of RNA polymerase (5, 6, 12), chief regulator of the general stress response in Escherichia coli (5, 12, 13). Further, a putative distal UP element half site (GTATTTGTTT) and a CAP site, thought to play a role in {sigma}S selectivity (3, 12, 13), are upstream of the –10 box. It is noteworthy that RAM contains at least two other ISAba-1-linked resistance genes (sul2 and ampC). Primer extension studies indicated that the extended promoter also drives transcription of sul2 (2). Albeit in a different strain of A. baumannii, this promoter was identified upstream of ampC (9) and it is assumed to be transcriptionally active with respect to ampC in strain RAM. The copy number and implied mobility of ISAba-1 in Acinetobacter spp. (8), combined with its repertoire of regulatory sequences, suggest that this element may play a significant role in controlling the expression of a variety of genes in Acinetobacter, even within a single strain of this organism.


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  		FIG. 1. Nucleotide sequence upstream of blaOXA-23 indicating transcription start sites (vertical arrows) of blaOXA-23 in A. baumannii (RAM) ({downarrow}) and E. coli(pRK001) ({uparrow}). Major transcription start sites are in bold. The promoters are boxed and double underlined. The sequence (underlined) upstream of TTATTT creates an extended –10 promoter. The blaOXA-23 start codon is boxed and shaded, and the left inverted repeat of ISAba-1 is in italics. The CAP site and UP element half site are underlined with dashed and dotted lines, respectively.

 
As transcription signals used in Acinetobacter are different from their counterparts in E. coli (10), primer extension studies were carried out to study the expression of blaOXA-23 in E. coli. The functional blaOXA-23 gene was amplified from RAM; cloned into pGEM-T EASY, generating pRK001; and expressed in E. coli JM109. Using RNA from E. coli(pRK001), five transcription start sites were identified (Fig. 1), corresponding to two major and three minor peaks. One of the major peaks mapped to a T which equates to the transcription start site identified upstream of blaOXA-23 in strain RAM; presumably, the transcript in E. coli(pRK001) also emanates from the extended –10 promoter. A different ISAba-1 promoter is present upstream of the second major start site (Fig. 1). These data indicate that although A. baumannii and E. coli possess related transcription machinery, at least one of the ISAba-1-located promoters is more active in E. coli than in A. baumannii.


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{triangledown} Published ahead of print on 4 June 2007. Back


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  1. Aiba, H., S. Adhya, and B. D. Crombugghe. 1981. Evidence for two functional gal promoters in intact Escherichia coli cells. J. Biol. Chem. 25:11905-11910.
  2. Garny, S. 2006. Distribution, frequency and contribution to the expression of antibiotic resistance gene of an IS element in Acinetobacter baumannii. M.S. thesis, University of Cape Town, South Africa.
  3. Germer, J., G. Becker, M. Metzner, and R. Hengge-Aronis. 2001. Role of activator site position and a distal UP-element half-site for sigma factor selectivity at a CRP/H-NS-activated {sigma}S-dependent promoter in Escherichia coli. Mol. Microbiol. 41:705-716.[CrossRef][Medline]
  4. Héritier, C., L. Poirel, T. Lambert, and P. Nordmann. 2005. Contribution of acquired carbapenem-hydrolyzing oxacillinases to carbapenem resistance in Acinetobacter baumannii. Antimicrob. Agents Chemother. 49:3198-3202.[Abstract/Free Full Text]
  5. Lacour, S., and P. Landini. 2004. {sigma}S-dependent gene expression at the onset of stationary phase in Escherichia coli: function of {sigma}S-dependent genes and identification of their promoter sequences. J. Bacteriol. 186:7186-7195.[Abstract/Free Full Text]
  6. Mitchell, J. E., D. Zheng, S. J. W. Busby, and S. D. Minchin. 2003. Identification and analysis of 'extended –10' promoters in Escherichia coli. Nucleic Acids Res. 31:4689-4695.[Abstract/Free Full Text]
  7. Segal, H., and B. G. Elisha. 2005. Use of Etest MBL strips for the detection of carbapenemases in Acinetobacter baumannii. J. Antimicrob. Chemother. 56:598.[Free Full Text]
  8. Segal, H., S. Garny, and B. G. Elisha. 2005. Is ISABA-1 customized for Acinetobacter? FEMS Microbiol. Lett. 243:425-429.[CrossRef][Medline]
  9. Segal, H., E. C. Nelson, and B. G. Elisha. 2004. Genetic environment and transcription of ampC in an Acinetobacter baumannii clinical isolate. Antimicrob. Agents Chemother. 48:612-614.[Abstract/Free Full Text]
  10. Segal, H., and B. G. Elisha. 1999. Characterization of the Acinetobacter plasmid, pRAY, and the identification of regulatory sequences upstream of an aadB gene cassette on this plasmid. Plasmid 42:60-66.[CrossRef][Medline]
  11. Turton, J. F., M. E. Ward, N. Woodford, M. E. Kaufmann, R. Pike, D. M. Livermore, and T. L. Pitt. 2006. The role of ISAba1 in expression of OXA carbapenemase genes in Acinetobacter baumannii. FEMS Microbiol. Lett. 258:72-77.[CrossRef][Medline]
  12. Typas, A., and R. Hengge. 2005. Differential ability of {sigma}S and {sigma}70 of Esche-richia coli to utilize promoters containing half or full UP-element sites. Mol. Microbiol. 55:250-260.[CrossRef][Medline]
  13. Weber, H., T. Polen, J. Heuveling, V. F. Wendisch, and R. Hengge. 2005. Genome-wide analysis of the general stress response network in Escherichia coli: {sigma}S-dependent genes, promoters, and sigma factor selectivity. J. Bacteriol. 187:1591-1603.[Abstract/Free Full Text]
Heidi Segal
Rachael K. Jacobson
Seike Garny
Colleen M. Bamford
B. Gay Elisha*
Division of Medical Microbiology
National Health Laboratory Service
University of Cape Town
Anzio Road, Observatory 7925
Cape Town, South Africa

* Phone: 27 21 4066378, Fax: 27 21 4066129, E-mail: gay.elisha{at}uct.ac.za

Antimicrobial Agents and Chemotherapy, August 2007, p. 3040-3041, Vol. 51, No. 8
0066-4804/07/$08.00+0     doi:10.1128/AAC.00594-07




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