Cap analogs containing 6-thioguanosine – reagents for the synthesis of mRNAs selectively photo-crosslinkable with cap-binding biomolecules

Abstract

Numerous biomolecules recognize the 7-methylguanosine cap structure present at the 5′ ends of eukaryotic mRNAs. Photo-crosslinking is a valuable technique to study these interactions. We report three anti-reverse cap analogs containing a photo-activable nucleoside, 6-thioguanosine (^6SG), that enable the synthesis of capped RNAs with ^6SG positioned exclusively as the first transcribed nucleotide. The effect of the 6-thioguanosine moiety on binding to the translation factor eIF4E and the efficiency of mRNA translation was determined. The utility of mRNAs with a ^6SG-modified cap in crosslinking experiments is shown by mapping the histone H4 cap-binding pocket.