Chemical Lithography: Selective Glyoxal Caging of mRNAs to Control Gene Expression

Achieving predictable, tunable, and temporal control over mRNA function would grant direct regulation of gene expression, facilitating the development of new therapeutics and biotechnologies. Although several approaches for stimuli-responsive control of nucleic acids have been explored, most are limited to short oligonucleotides, lack a timed-release mechanism, or both. We envisioned a complementary method using glyoxal as a caging reagent. Glyoxal readily reacts with amidine groups found on the faces of nucleobases to give stable bis-hemiaminal adducts, directly disrupting hydrogen bonding. Fortuitously, this reaction is readily reversible, enabling spontaneous time-release decaging that varies with temperature. However, when applied previously to full-length mRNAs, the sequence length and excessive adduct formation resulted in no reactivation under relevant physiological conditions. To address this challenge, we developed chemical lithography in which portions of longer RNAs are "masked" through hybridization to complementary DNAs, permitting selective caging on only non-masked regions and preventing excessive adduct formation. We present an optimized glyoxalation protocol applied to EGFP as a model mRNA sequence and evaluate masking effectiveness through qualitative and quantitative studies. Using EGFP fluorescence, we monitored and assessed the ability of selective glyoxalation to control gene expression over time in vitro. We demonstrate the direct dependence of both the initial inhibited expression and the respective activity recovery based on the amount and location of glyoxalation. We also highlight distinct caging patterns exhibiting total inhibition upon initial treatment and complete reactivation following decaging. We anticipate that this approach will improve the mechanistic study of mRNA and gene expression and also facilitate new investigations and methods within chemical biology and biomedicine.