Riboswitches, thermosensors, and T-boxes Flashcards
What is a riboswitch?
An RNA sequence that will change its secondary structure in response to binding to small metabolites, which will then alter gene expression through transcription attenuation or blocking translation
What are 5 metabolites used by riboswitches?
- Amino acids
- Vitamins
- Nucleic acid bases
- Flavin mononucleotide (FMN)
- Metal ions
What is the relationship between the metabolite used by a riboswitch and the genes that it regulates?
Often the genes regulated will have something to do with that metabolite. Like genes involved in metal homeostasis may use a riboswitch that responds to metal ions
How do riboswitch works?
One secondary structure will be more stable and will form when the riboswitch isn’t binding the metabolite. Then it will change to the less stable secondary structure when the metabolite binds. It will then alter transcription attenuation through the hairpins
What is a thermosensor?
A leader sequence that changes secondary structure in response to a change in temperature
What happens to the virulence gene thermosensors at low temperature in Listeria?
They form a hairpin that sequesters the ribosome binding site, preventing expression of the virulence genes outside the host
What happens to the virulence gene thermosensors at higher temperature in Listeria?
The PrfA transcription factor can bind to the alternate conformation, which then exposes the ribosome binding site
What is a T-box?
A type of riboswitch that is mediated by tRNAs
What type of genes tend to T-box riboswitches?
Genes that encode amino acid biosynthesis enzymes, transport proteins, and aminoacyl-tRNA-synthetases
What changes the secondary structure of T-boxes?
The concentration of charged tRNAs (tRNA with an amino acid stuck on it), which acts as a sensor for the level of amino acid in the cells
