CID 2818500 (trans-α-Nitrostilbene; 1,1μ-[(1Z)-1-Nitro-1,2-ethenediyl]bis-benzene) is a selective inhibitor of Protein Arginine Methyltransferases PRMT1 and PRMT8. PRMT1 is responsible for the majority of arginine methylation in the cell involved in transcription, chromatin modification, and signal transduction. CID 2818500 has an IC50 values of 11 μM for PRMT1, and does not inhibit PRMTs 3, 4, and 6, although it does inhibit PRMT8. The mechanism is believed to involve a specific S-adenosylmethionine (SAM)-binding cysteine present only in the Type I PRMTs PRMT1 and PRMT8 and absent in other SAM-dependent methyltransferases.