The ''dinQ-agrB'' type I toxin-antitoxin (TA) system was initially identified in ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...

''. This type I TA system is induced by the bacterial

DNA damage DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...

response system known as the SOS response system.

''dinQ''

''dinQ'', DNA-damage-inducible protein Q produces two major transcripts, only one, however, +44, is actively

translated Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...

. Translation is initiated using the unusual GUG

start codon The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and Archaea and a N-formylmethionine (fMet) in bacteria, mitochondria and plastids. The ...

and results in a 27

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A ...

. Plasmid-based expression of C-terminal triple FLAG-tagged ''dinQ'' located DinQ in the inner-membrane of ''E. coli''. Overexpression of ''dinQ'' led to reduced survival, loss of transmembrane electrical polarity and reduced intracellular

ATP ATP may refer to: Companies and organizations * Association of Tennis Professionals, men's professional tennis governing body * American Technical Publishers, employee-owned publishing company * ', a Danish pension * Armenia Tree Project, non ...

concentrations.

''agrA'' and ''agrB''

''agrA'' and ''agrB'' are two small RNAs, 84

ribonucleotides In biochemistry, a ribonucleotide is a nucleotide containing ribose as its pentose component. It is considered a molecular precursor of nucleic acids. Nucleotides are the basic building blocks of DNA and RNA. Ribonucleotides themselves are basic mo ...

long, named due to their position in the ''

E. coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...

'' genome (arsR-gor region

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

A and B). 31 ribonucleotides at the

5'-end Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. In a single strand of DNA or RNA, the chemical convention of naming carbon atoms in the nucleotide pentose-sugar-ri ...

of ''agrA'' and ''agrB'' show partial sequence complementarity within the primary transcript of ''dinQ'', 25 for ''agrA'' and 30 for ''agrB'' being identical. Only deletion of the ''agrB'' gene led to an increase in sensitivity to DNA-damaging

UV light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

, the ''agrB'' mutant also grew slower than the wild-type ''E. coli'' and failed to decompact its chromosomal DNA following a short non-lethal exposure to DNA-damaging UV.

''agrB'' inhibition of ''dinQ'' translation

''agrB'' functions by binding to the translationally active ''dinQ'' transcript, +44, and, in so doing, stabilises the intramolecular sequestration of the Shine-Dalgarno translation initiation sequence. Additionally, ''agrB'' preferentially facilitates the endoribonucleolytic cleavage of the +44 ''dinQ'' transcript by RNase III as opposed to the primary +1 transcript.

References

{{reflist Non-coding RNA