SymR RNA
Encyclopedia
SymR RNA is a non-coding RNA
which forms a type I toxin-antitoxin system along with the protein SymE. SymR was originally labelled RyjC and is a 77nt
RNA with a σ70
promoter. RyjC was found to overlap the yjiW open reading frame
on the opposite strand by 6nt, and was characterised as an antisense RNA which bound the 5' untranslated region
of yjiW. Further study led to the renaming of both yjiW and RyjC to SymE (SOS-induced yjiW gene with similarity to MazE) and SymR (symbiotic
RNA) respectively.
SymR blocks translation
of SymE by antisense binding. SymE exhibits its toxicity by repressing global translation within the cell
, cleaving mRNA in a similar manner to MazE toxin. Quantative Northern blot
experiments showed that SymR RNA is present in cells at 10 times the concentration of SymE mRNA (0.02 fmol
μg−1 and 0.2 fmol μg−1).
Following DNA damage, the SOS response
represses transcription
of SymR RNA, allowing SymE toxin to degrade potentially damaged mRNA until the DNA has been repaired
.
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...
which forms a type I toxin-antitoxin system along with the protein SymE. SymR was originally labelled RyjC and is a 77nt
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
RNA with a σ70
Sigma factor
A sigma factor is a bacterial transcription initiation factor that enables specific binding of RNA polymerase to gene promoters. Different sigma factors are activated in response to different environmental conditions...
promoter. RyjC was found to overlap the yjiW open reading frame
Open reading frame
In molecular genetics, an open reading frame is a DNA sequence that does not contain a stop codon in a given reading frame.Normally, inserts which interrupt the reading frame of a subsequent region after the start codon cause frameshift mutation of the sequence and dislocate the sequences for stop...
on the opposite strand by 6nt, and was characterised as an antisense RNA which bound the 5' untranslated region
Five prime untranslated region
A messenger ribonucleic acid molecule codes for a protein through translation. The mRNA also contains regions that are not translated: in eukaryotes these include the 5' untranslated region, 3' untranslated region, 5' cap and poly-A tail....
of yjiW. Further study led to the renaming of both yjiW and RyjC to SymE (SOS-induced yjiW gene with similarity to MazE) and SymR (symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
RNA) respectively.
SymR blocks translation
Translation (genetics)
In molecular biology and genetics, translation is the third stage of protein biosynthesis . In translation, messenger RNA produced by transcription is decoded by the ribosome to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein...
of SymE by antisense binding. SymE exhibits its toxicity by repressing global translation within the cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
, cleaving mRNA in a similar manner to MazE toxin. Quantative Northern blot
Northern blot
The northern blot is a technique used in molecular biology research to study gene expression by detection of RNA in a sample. With northern blotting it is possible to observe cellular control over structure and function by determining the particular gene expression levels during differentiation,...
experiments showed that SymR RNA is present in cells at 10 times the concentration of SymE mRNA (0.02 fmol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
μg−1 and 0.2 fmol μg−1).
Following DNA damage, the SOS response
SOS response
The SOS response is a global response to DNA damage in which the cell cycle is arrested and DNA repair and mutagenesis are induced. The SOS uses the RecA protein . The RecA protein, stimulated by single-stranded DNA, is involved in the inactivation of the LexA repressor thereby inducing the response...
represses transcription
Transcription (genetics)
Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...
of SymR RNA, allowing SymE toxin to degrade potentially damaged mRNA until the DNA has been repaired
DNA repair
DNA repair refers to 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 UV light and radiation can cause DNA damage, resulting in as many as 1...
.