Hydrolytic activity of human Nudt16 enzyme on dinucleotide cap analogs and short capped oligonucleotides

Human Nudt16 (hNudt16) is a member of the Nudix family of hydrolases, comprising enzymes catabolizing various substrates including canonical (d)NTPs, oxidized (d)NTPs, nonnucleoside polyphosphates, and capped mRNAs. Decapping activity of the Xenopus laevis (X29) Nudt16 homolog was observed in the nucleolus, with a high specificity toward U8 snoRNA. Subsequent studies have reported cytoplasmic localization of mammalian Nudt16 with cap hydrolysis activity initiating RNA turnover, similar to Dcp2. The present study focuses on hNudt16 and its hydrolytic activity toward dinucleotide cap analogs and short capped oligonucleotides. We performed a screening assay for potential dinucleotide and oligonucleotide substrates for hNudt16. Our data indicate that dinucleotide cap analogs and capped oligonucleotides containing guanine base in the first transcribed nucleotide are more susceptible to enzymatic digestion by hNudt16 than their counterparts containing adenine. Furthermore, unmethylated dinucleotides (GpppG and ApppG) and respective oligonucleotides (GpppG-16nt and GpppA-16nt) were hydrolyzed by hNudt16 with greater efficiency than were m⁷GpppG and m⁷GpppG-16nt. In conclusion, we found that hNudt16 hydrolysis of dinucleotide cap analogs and short capped oligonucleotides displayed a broader spectrum specificity than is currently known.