derepressing

Derepressing, or derepression, is the process by which genes that are repressed become transcriptionally active. It involves lifting or neutralizing the mechanisms that suppress transcription, allowing RNA polymerase to access the promoter and initiate gene expression. Derepression can occur in various biological contexts and is often part of broader regulatory responses.

In bacteria and archaea, derepression commonly results from inactivation or removal of a repressor protein. This can occur when a small molecule (an inducer) binds to the repressor and changes its conformation, reducing its affinity for the operator. Other routes include proteolytic degradation of the repressor or the action of anti-repressors, which counteract repressors and permit transcription without new synthesis of activators.

In eukaryotes, derepression frequently involves changes to chromatin structure and epigenetic marks. Repressed chromatin can be opened by histone acetylation, chromatin remodeling complexes, or removal of DNA methylation, making promoters more accessible to transcriptional machinery. Environmental signals, development, and cellular stress can trigger such chromatin-relaxing events, leading to derepression of gene sets.

Derepression is related to, but not always synonymous with, induction. Induction describes the activation of gene expression via inducers that promote transcription, while derepression specifically emphasizes the removal of repression itself. The term highlights reversibility: derepressed genes may revert to a repressed state if repressive conditions return.

See also: repression, induction, chromatin remodeling, epigenetics, operon regulation.