Programmable protein expression using a genetically encoded m⁶A sensor

The N⁶-methyladenosine (m⁶A) modification is found in thousands of cellular mRNAs and is a critical regulator of gene expression and cellular physiology. m⁶A dysregulation contributes to several human diseases, and the m⁶A methyltransferase machinery has emerged as a promising therapeutic target. However, current methods for studying m⁶A require RNA isolation and do not provide a real-time readout of mRNA methylation in living cells. Here we present a genetically encoded m⁶A sensor (GEMS) technology, which couples a fluorescent signal with cellular mRNA methylation. GEMS detects changes in m⁶A caused by pharmacological inhibition of the m⁶A methyltransferase, giving it potential utility for drug discovery efforts. Additionally, GEMS can be programmed to achieve m⁶A-dependent delivery of custom protein payloads in cells. Thus, GEMS is a versatile platform for m⁶A sensing that provides both a simple readout for m⁶A methylation and a system for m⁶A-coupled protein expression.