Die stark wachsende chemische Vielfalt der RNA-Modifikationen enthält eine Thioacetalstruktur

Identification of 2-Methylthio-methylenethio-N6 -(cis-4-hydroxyisopentenyl)adenosine (msms2 io6 A37 ) as a Novel Modification at Adenosine 37 of tRNAs from Salmonella typhimurium

Post-transcriptional modifications of tRNA nucleotide are important determinants in folding, structure and function. We have successfully identified and characterized a new modified base named 2-methylthio-methylenethio-N⁶ -(cis-4-hydroxyisopentenyl)adenosine, which is present at position 37 in some tRNAs. We also showed that this new modified adenosine is derived from the known 2-methylthio-methylenethio-N⁶ -(isopentenyl)adenosine nucleoside by a catalytic cycle of the tRNA-diiron monooxygenase, MiaE, present in Salmonella typhimurium.

A New Bacterial Adenosine-Derived Nucleoside as an Example of RNA Modification Damage

The fields of RNA modification and RNA damage both exhibit a plethora of non-canonical nucleoside structures. While RNA modifications have evolved to improve RNA function, the term RNA damage implies detrimental effects. Based on stable isotope labelling and mass spectrometry, we report the identification and characterisation of 2-methylthio-1,N6-ethenoadenosine (ms² ϵA), which is related to 1,N6-ethenoadenine, a lesion resulting from exposure of nucleic acids to alkylating chemicals in vivo. In contrast, a sophisticated isoprene labelling scheme revealed that ms² ϵA biogenesis involves cleavage of a prenyl moiety in the known transfer RNA (tRNA) modification 2-methylthio-N6-isopentenyladenosine (ms² i⁶ A). The relative abundance of ms² ϵA in tRNAs from translating ribosomes suggests reduced function in comparison to its parent RNA modification, establishing the nature of the new structure in a newly perceived overlap of the two previously separate fields, namely an RNA modification damage.