Inhibitory study of protein arginine methyltransferase 1 using a fluorescent approach

Protein arginine methyltransferases (PRMTs) play important roles in both normal physiology and human diseases. Deregulation of PRMT activity has been linked to several pathological states such as cancer and cardiovascular disorders. Herein, we report our work of designing and using new fluorescent reporters to perform single-step analysis of substrate binding and methylation by PRMT1. Both fluorescence intensity and anisotropy of the two reporters, R4-FL and H4-FL, were shown to effectively manifest enzyme-substrate interactions, highlighting their application in investigating PRMT inhibitors. In particular, the methylation process of R4-FL can be directly studied using fluorescence intensity readout. By combining the fluorescent measurement with radioactive analysis, we determined that AMI-1 inhibits PRMT1 activity through the mechanism of blocking peptide substrate binding.