Molecular mechanisms of pressure-regulation at transcription level in piezophilic bacteria

摘要

Deep-sea bacteria have unique systems for gene and protein expression controlled by hydrostatic pressure. One of the σ factors, σ~(54), was found to play an important role on the pressure-regulated transcription in a deep-sea piezophilic bacterium, Shewanella violacea. A glutamine synthetase gene (glnA) has been targeted as a model for the pressure-regulated promoter to investigate the transcriptional regulation by the σ~(54) factor. Recognition sites for σ~(54) and σ~(70) factors were observed at an upstream region of the glnA and also NtrC-binding sites were identified at this same region. Primer extension analyses revealed that the transcription initiation sites of both promoters were determined and that the transcription from the σ~(54) site was regulated by elevated pressure. The σ~(54) promoter is known to be activated by a two components signal transduction system, NtrB-NtrC phospholylated relay. Our results suggested that this system might be regulated by deep-sea conditions and that the gene expression controlled by the σ~(54) promoter was actually regulated by pressure. We proposed a possible model of the molecular mechanisms for pressure-regulated transcription.