Effect of polyamines and synthetic polyamine-analogues on the expression of antizyme (AtoC) and its regulatory genes

BACKGROUND: In bacteria, the biosynthesis of polyamines is modulated at the level of transcription as well as post-translationally. Antizyme (Az) has long been identified as a non-competitive protein inhibitor of polyamine biosynthesis in E. coli. Az was also revealed to be the product of the atoC gene. AtoC is the response regulator of the AtoS-AtoC two-component system and it functions as the positive transcriptional regulator of the atoDAEB operon genes, encoding enzymes involved in short chain fatty acid metabolism. The antizyme is referred to as AtoC/Az, to indicate its dual function as both a transcriptional and post-translational regulator. RESULTS: The roles of polyamines on the transcription of atoS and atoC genes as well as that of atoDAEB(ato) operon were studied. Polyamine-mediated induction was tested both in atoSC positive and negative E. coli backgrounds by using β-galactosidase reporter constructs carrying the appropriate promoters patoDAEB, patoS, patoC. In addition, a selection of synthetic polyamine analogues have been synthesized and tested for their effectiveness in inducing the expression of atoC/Az, the product of which plays a pivotal role in the feedback inhibition of putrescine biosynthesis and the transcriptional regulation of the ato operon. The effects of these compounds were also determined on the ato operon expression. The polyamine analogues were also tested for their effect on the activity of ornithine decarboxylase (ODC), the key enzyme of polyamine biosynthesis and on the growth of polyamine-deficient E. coli. CONCLUSION: Polyamines, which have been reported to induce the protein levels of AtoC/Az in E. coli, act at the transcriptional level, since they cause activation of the atoC transcription. In addition, a series of polyamine analogues were studied on the transcription of atoC gene and ODC activity

Turbulente Ränder: Konturen eines neuen Migrationsregimes im Südosten Europas

This article reviews developments of a new migration regime in Europe. It argues against the concept of a 'Fortress Europe' by pointing to fields of conflict that current migration movements establish. By focussing on a recent field research of migrations movements in Southeast Europe it explores modes of transit and entrepreneurial migration, the transformation and implementation of asylum laws, and the manifold functions of camps in the context of a transformation of statehood in this region

Turbulent Margins. Outlines of a new migration regime in Southeast Europe. (Turbolente Raender. Konturen eines neuen migrationsregimes in Suedosten Europas)

This article reviews developments of a new migration regime in Europe. It argues against the concept of a 'Fortress Europe' by pointing to fields of conflict that current migration movements establish. By focussing on a recent field research of migrations movements in Southeast Europe it explores modes of transit and entrepreneurial migration, the transformation and implementation of asylum laws, and the manifold functions of camps in the context of a transformation of statehood in this region

Turbulent Margins. Outlines of a new migration regime in Southeast Europe. (Turbolente Raender. Konturen eines neuen migrationsregimes in Suedosten Europas)

This article reviews developments of a new migration regime in Europe. It argues against the concept of a 'Fortress Europe' by pointing to fields of conflict that current migration movements establish. By focussing on a recent field research of migrations movements in Southeast Europe it explores modes of transit and entrepreneurial migration, the transformation and implementation of asylum laws, and the manifold functions of camps in the context of a transformation of statehood in this region

Interactions of the Antizyme AtoC with Regulatory Elements of the Escherichia coli atoDAEB Operon▿

AtoC has a dual function as both an antizyme, the posttranslational inhibitor of polyamine biosynthetic enzymes, and the transcriptional regulator of genes involved in short-chain fatty acid catabolism (the atoDAEB operon). We have previously shown that AtoC is the response regulator of the AtoS-AtoC two-component signal transduction system that activates atoDAEB when Escherichia coli is exposed to acetoacetate. Here, we show that the same cis elements control both promoter inducibility and AtoC binding. Chromatin immunoprecipitation experiments confirmed the acetoacetate-inducible binding of AtoC to the predicted DNA region in vivo. DNase I protection footprinting analysis revealed that AtoC binds two 20-bp stretches, constituting an inverted palindrome, that are located at −146 to −107 relative to the transcription initiation site. Analyses of promoter mutants obtained by in vitro chemical mutagenesis of the atoDAEB promoter verified both the importance of AtoC binding for the inducibility of the promoter by acetoacetate and the σ54 dependence of atoDAEB expression. The integration host factor was also identified as a critical component of the AtoC-mediated induction of atoDAEB