We found that Escherichia coli MazF toxin, an ACA-sequence-specific endoribonuclease, was sensitive to N-methyladenosine (m6A), representing the first m6A-sensitive RNA cleavage enzyme. The methyl-sensitivity of MazF allowed simple analyses of both m6A demethylase and methyltransferase activity. Furthermore, the approach could be used for inhibitor screening.

Delivery of biomacromolecules via endocytic pathways requires the efficient accumulation of cargo molecules into endosomes, followed by their release to the cytosol. We propose a unique intracellular delivery strategy for bioactive molecules using a new potent macropinocytosisinducing peptide derived from stromal-derived factor (SDF)-1α (SN21). This peptide allowed extracellular materials to enter cells through the activation of macropinocytosis. To provide the ability to release internalized cargoes from endosomes, we conjugated SN21 with membranelytic peptides. The combination of a macropinocytosis-inducing peptide and a membrane lytic peptide successfully delivered functional siRNA and proteins, which include antibodies, Cre recombinase, and an artificial transcription regulator protein having a transcription activator-like effector (TALE) motif. This study shows the feasibility of combining physiological stimulation of macropinocytosis with physicochemical disruption of endosomes as a strategy for intracellular delivery.

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