Control of expression of the ICE R391 encoded UV-inducible cell-sensitising function

BMC Microbiology

J Tony Pembroke¹  Patricia Armshaw¹ 

[1] Molecular and Structural Biochemistry Laboratory, Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland

关键词: UV-induced sensitisation and cytotoxicity;    Conjugative transfer;    Type IV secretion system;    SXT/R391 ICE;   

Others  :  1143173
DOI  :  10.1186/1471-2180-13-195

 received in 2013-04-08, accepted in 2013-08-28,  发布年份 2013

【 摘 要 】

Background

Many SXT/R391-like enterobacterial Integrative Conjugative Elements (ICEs) have been found to express an atypical, recA-dependent, UV-inducible, cell-sensitising phenotype observed as a reduction in post-irradiation cell survival rates in host cells. Characterisation of a complete deletion library of the prototype ICE R391 identified the involvement of three core ICE genes, orfs90/91 encoding a putative transcriptional enhancer complex, and orf43, encoding a putative type IV secretion system, outer membrane-associated, conjugative transfer protein.

Results

In this study, expression analysis of orf43 indicated that it was up-regulated as a result of UV irradiation in an orfs90/91-dependent manner. Induced expression was found to be controlled from a site preceding the gene which required functional orfs90/91. Expression of orfs90/91 was in turn found to be regulated by orf96, a λ cI-like regulator. Targeted construction of ICE R391 deletions, RT-PCR and qRT-PCR analysis confirmed a regulatory link between orfs90/91 and orf43 while site-directed mutagenesis of orf43 suggested an association with the cell membrane was a prerequisite for the cytotoxic effect.

Conclusions

Because of the recA-dependence of the effect, we hypothesise that UV induction of RecA results in cleavage of the cI-like ICE-encoded repressor protein, the product of orf96. This in turn allows expression of the transcriptional enhancer complex encoded by orfs90/91, which we conclude stimulates transcription of orf43, whose product is directly responsible for the effect.

【 授权许可】

   
2013 Armshaw and Pembroke; licensee BioMed Central Ltd.

【 图 表 】

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