“…In general, the most common type of regulatory mechanism by trans-asRNAs is translation repression, but a few notable examples for an activating mode of action have been described. [102][103][104][105] In addition, mRNAs, specifically their 5'UTR, can function as a direct sensor for the physical and metabolic state of the cell. One class of cis-regulatory elements, the riboswitches, responds to trans-acting ligands such as the intracellular concentration of metabolites (i.e., nucleobases, coenzymes, sugars, amino acids) and metal ions.…”