English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Because of their ability to stimulate gene expression from distant sites and regardless of their orientation, transcriptional enhancer elements are a puzzling class of regulatory DNA sequences (42). Although enhancers are a common feature of eukaryotic and viral genes, the mechanism by which they communicate with promoters and stimulate gene expression is still not very well understood. However, our understanding of the mechanism of gene activation at a distance has been boosted by the study of naturally occurring enhancer-like elements (ELE) in prokaryotes. The ELE are palindromic or nearly palindromic nucleotide sequences normally found between 100 and 200 bp upstream of a certain class of promoters, and, like the eukaryotic enhancers, they still stimulate transcription when moved thousands of nucleotides upstream or downstream from the transcription start and regardless of their orientation (7, 47). The extensive genetic characterization of many bacterial ELE and the development of defined in vitro transcription systems has greatly facilitated the study of activation by enhancers, and now some of the molecular details of distal activation are well established (34). It has been demonstrated that the ELE are binding sites for regulatory proteins named bacterial enhancer-binding proteins (EBPs). The best-studied EBPs are NtrC and NifA, which stimulate the expression of genes required for nitrogen assimilation and nitrogen fixation, respectively, in a number of organisms (37). These proteins activate genes transcribed by the RNA polymerase holoenzyme containing the alternative sigma factor &F4 (EO(J4). The u54 system is widely represented in the alpha and gamma proteobacteria (previously called purple bacteria), and it has also been reported to be present in Bacillus subtilis (13, 14). Among other physiological processes controlled by C54 are nitrogen assimilation and fixation, dicarboxylic acid transport, hydrogen oxidation, alginate utilization, degradation of aromatic compounds, pilus formation and formate utilization (for reviews, see references 35 and 56). A common feature of all these processes is that they are not absolutely required for cell survival, and each is activated by a different EBP interacting with a distinctive ELE nucleotide sequence. In addition to its ability to be activated at a distance, the Er54 system has several other unique characteristics that are not common among bacterial holoenzymes. E&'4 recognizes promoter DNA with unusually close boxes, centered at

The sigma 54 bacterial enhancer-binding protein family: mechanism of action and phylogenetic relationship of their functional domains