The rnc operon is negatively auto-regulated by transcript stability. rnc, the first gene in the operon codes for RNase III which cleaves the long rncO stem II leading to transcript degradation and a reduction in translation.
In the context of the rnc operon, negative auto-regulation is achieved through the stabilization of transcripts, where the RNC gene's product, RNase III, degrades the long rncO secondary structure, resulting in reduced protein synthesis and mRNA stability.