RncO is a bacterial non-coding RNA

Non-coding RNA

A non-coding RNA is a functional RNA molecule that is not translated into a protein. Less-frequently used synonyms are non-protein-coding RNA , non-messenger RNA and functional RNA . The term small RNA is often used for short bacterial ncRNAs...

 regulatory element found in the rnc leader sequence. The rnc operon

Operon

In genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal or promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo trans-splicing to create...

 is negatively auto-regulated by transcript stability. rnc, the first gene in the operon codes for RNase III

RNase III

RNase III enzymes specifically bind to and cleave double-stranded RNA . There are three subdivisions, known as Class 1, 2, and 3.Prokaryotic ribonuclease III is an enzyme that digests double-stranded RNA. It is involved in the processing of ribosomal RNA precursors and of some mRNAs.* Class 1...

 which cleaves the long rncO stem

Stem-loop

Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded DNA or, more commonly, in RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when read in opposite directions,...

 II leading to transcript degradation and a reduction in translation. Matsunaga et al. showed that RNase III

RNase III

RNase III enzymes specifically bind to and cleave double-stranded RNA . There are three subdivisions, known as Class 1, 2, and 3.Prokaryotic ribonuclease III is an enzyme that digests double-stranded RNA. It is involved in the processing of ribosomal RNA precursors and of some mRNAs.* Class 1...

 cleavage can initiate rnc transcript decay independently of rnc gene translation. Further work has established that rncO structure and function is conserved

Conserved sequence

In biology, conserved sequences are similar or identical sequences that occur within nucleic acid sequences , protein sequences, protein structures or polymeric carbohydrates across species or within different molecules produced by the same organism...

 in Salmonella typhimurium.

Structure

Functionally the first 215 nucleotides of the rnc leader have been shown to be sufficient. Within this region three stem-loop

Stem-loop

Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded DNA or, more commonly, in RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when read in opposite directions,...

s were identified. Stem-loop II is cleaved by RNase III, whereas stem-loops I and III are important for stability.