Opéron

Opéron is the French term for the genetic unit known in English as the operon. It denotes a functioning stretch of DNA that contains a cluster of genes under the control of a single promoter and is regulated as a unit, allowing coordinated expression of genes involved in a common pathway.

An opéron typically includes a promoter, an operator region where regulatory proteins bind, and one or more structural genes that encode proteins for a shared function. A regulatory gene (which can be located nearby or elsewhere in the genome) may produce a repressor or activator that modulates transcription. Some opérons also contain regulatory elements such as an attenuator, which can influence transcription termination.

Regulation of opérons occurs mainly through two modes: inducible and repressible. Inducible opérons, such as the lac operon in Escherichia coli, are activated in response to an inducer that alleviates repression. Repressible opérons, such as the trp operon, are turned off when the end product is plentiful, via a repressor–cofactor complex. Attenuation provides an additional layer of control in some repressible opérons, using leader sequences to terminate transcription under specific conditions.

Distribution and significance vary. The opéron concept is a hallmark of prokaryotic gene regulation, enabling efficient, coordinated expression of genes for a pathway. Most eukaryotes transcribe genes individually, but operon-like gene clusters exist in a few organisms and have influenced the study of gene regulation and synthetic biology.

Historically, the operon model was proposed by François Jacob and Jacques Monod in 1961, based on experiments with lactose utilization in bacteria, and has shaped modern understanding of transcriptional regulation.