RNA modification is a well-recognized way for gene expression regulation in a living cell. Natural enzymatic RNA modifications have been characterized for decades. Recently, additional mechanisms, more related to RNA damage, have emerged, which do not involve targeted enzymatic activity but nonetheless alter the chemical structure of nucleosides. Aberrantly modified RNA may also appear due to incomplete or erroneous enzymatic reactions. We demonstrate that tRNA-guanine transglycosylase (TGT) …