Metal‐responsive RNA polymerase extracytoplasmic function (ECF) sigma factors

Abstract

In order to survive, bacteria must adapt to multiple fluctuations in their environment, including coping with changes in metal concentrations. Many metals are essential for viability, since they act as cofactors of indispensable enzymes. But on the other hand, they are potentially toxic because they generate reactive oxygen species or displace other metals from proteins, turning them inactive. This dual effect of metals forces cells to maintain homeostasis using a variety of systems to import and export them. These systems are usually inducible, and their expression is regulated by metal sensors and signal-transduction mechanisms, one of which is mediated by extracytoplasmic function (ECF) sigma factors. In this review, we have focused on the metalresponsive ECF sigma factors, several of which are activated by iron depletion (FecI, FpvI and PvdS), while others are activated by excess of metals such as nickel and cobalt (CnrH), copper (CarQ and CorE) or cadmium and zinc (CorE2). We focus particularly on their physiological roles, mechanisms of action and signal transduction pathways.

Predicting antimicrobial mechanism-of-action from transcriptomes: A generalizable explainable artificial intelligence approach

“…As membrane/transport GO terms were expected to be enriched in gene sets that classify MOA targets related to cellular structure and nucleotide/protein binding related terms were expected for gene product synthesis, we were not expecting a multitude of metal ion related GO terms in the classification of protein-synthesis and rna-polymerase inhibitors. However, this agrees with previous studies that have focused on metal-responsive ECF sigma factors, several of which are activated by iron depletion or by an excess of other metals such as zinc [30]; thus, overlapping with the GO terms enriched in our GSEA analysis (S5 Table ). Bacterial ECF sigma factors are directly involved in the transcription process by recognizing promoter sequences, together with the core RNA polymerase enzyme, and initiate the transcription of the genes they regulate [31].…”

Insight into the biology of Mycobacterium mucogenicum and Mycobacterium neoaurum clade members

“…fosfomycin 67 . The cnrH genes were predicted as homologs of cnrH present in Cupriavidus metallidurans CH34 where it is part of a circuit regulating resistance to metals, in particular nickel 68,69 . Together this raises the possibility that stationary Mmuc T cells are prepared to “face” exposure to antibiotics such as fosfomycin and nisin as well as nickel.…”

ECF σ factors with regulatory extensions: the one‐component systems of the σ universe

“…Hence, the C‐terminal extension also plays an essential role in regulating the activity of ECF44 σ factor, in line with the results obtained for ECF41 and ECF42. More detailed information on ECF44 σ factors can be found in the accompanying review on metal‐responsive ECFs in this issue (Moraleda‐Munoz et al ., ).…”