RegA

regA is a gene symbol used in multiple organisms to designate regulators of gene expression or signaling pathways. Because it is employed in diverse species, regA does not correspond to a single conserved function, but rather to distinct regulatory roles that have evolved independently in different lineages.

In certain bacteria, notably the RegB/RegA two-component system, regA encodes a response regulator that controls transcription of photosynthesis-related genes in response to redox conditions. RegB acts as the sensor kinase and phosphorylates RegA, which then binds to promoter regions to activate or repress target genes under anaerobic or low-oxygen conditions. The protein typically features a receiver domain that accepts phosphate and a C-terminal DNA-binding domain that mediates transcriptional regulation.

In the social amoeba Dictyostelium discoideum, regA encodes a cyclic adenosine monophosphate (cAMP) phosphodiesterase that modulates intracellular cAMP signaling during development. By altering cAMP levels, RegA influences developmental processes such as aggregation and differentiation, helping coordinate the transition from unicellular to multicellular states.

Across other species, regA can denote genes with related or entirely different regulatory roles. The common thread is that regA refers to a regulatory component involved in sensing, signaling, or transcriptional control, rather than a single universal mechanism. When encountered, the specific function of regA should be interpreted in the context of the organism and associated regulatory networks. See also RegB/RegA two-component systems for a well-characterized bacterial example.