A Potent, Selective and Cell‐Active Allosteric Inhibitor of Protein Arginine Methyltransferase 3 (PRMT3)

Abstract

PRMT3 catalyzes the asymmetric dimethylation of arginine residues of various proteins. It is essential for maturation of ribosomes, may have a role in lipogenesis, and is implicated in several diseases. A potent, selective, and cell- active PRMT3 inhibitor would be a valuable tool for further investigating PRMT3 biology. Here we report the discovery of the first PRMT3 chemical probe, SGC707, by structure-based optimization of the allosteric PRMT3 inhibitors we reported previously, and thorough characterization of this probe in biochemical, biophysical, and cellular assays. SGC707 is a potent PRMT3 inhibitor (IC50 = 31 ± 2 nm, KD = 53 ± 2 nm) with outstanding selectivity (selective against 31 other methyltransferases and more than 250 non-epigenetic targets). The mechanism of action studies and crystal structure of the PRMT3-SGC707 complex confirm the allosteric inhibition mode. Importantly, SGC707 engages PRMT3 and potently inhibits its methyltransferase activity in cells. It is also bioavailable and suitable for animal studies. This well- characterized chemical probe is an excellent tool to further study the role of PRMT3 in health and disease.

Inhibition of protein arginine methyltransferase 3 activity selectively impairs liver X receptor‐driven transcription of hepatic lipogenic genes in vivo

“…The mice received palm oil to further induce hepatic steatosis and ensure optimal stimulation of PRMT3 translocation to the nucleus (Chisholm et al ., 2003; Go et al ., 2015; Kim et al ., 2015a). To determine the effect of PRMT3 inhibition under these steatosis‐inducing conditions, mice were treated for 4 days with a total of three injections of SGC707 (30 mg·kg −1 ), which was the dose recommended for in vivo usage (Kaniskan et al ., 2015). An additional experimental group was included to assess the effectiveness of a lower dosage of 10 mg·kg −1 of SGC707.…”

“…SGC707 thus is a highly potent inhibitor of PRMT3 in vivo and therefore confirms previous studies investigating the effect of SGC707 on PRMT3 activity (Kaniskan et al ., 2015). Further studies should be conducted to investigate the molecular mechanisms underlying the PRMT3–LXR interaction and selective effects on gene expression in detail.…”

Dysregulation of histone methyltransferases in breast cancer – Opportunities for new targeted therapies?

“…The exception to this is KMT2E/MLL5, which lacks intrinsic methyltransferase activity (Rao and Dou, 2015). Analysis of large-scale data sets such as TCGA (Kandoth et al, 2013;Liu et al, 2015) and COS-MIC (Kudithipudi and Jeltsch, 2014;Rao and Dou, 2015) has identified KMT2 family members as among the most frequently mutated genes in human cancer.…”

A Chemical Biology Toolbox for the Study of Protein Methyltransferases and Epigenetic Signaling

“…A third class of inhibitors has allosteric mechanisms that can induce long-range structural perturbations, or take advantage of sites of protein-protein interactions within multi-subunit PMT complexes. The allosteric inhibitor SGC707 (Kaniskan et al, 2015) occupies a pocket that is 15 Å away from the site of methyl transfer, but prevents formation of the catalytically competent conformation of the PRMT3 dimer (Figure 2C, top panel). OICR-9429 (Grebien et al, 2015) and A-395 (He et al, 2017) are antagonists that make use of the peptide binding pocket in the essential WD40 subunits (WDR5 and EED) of the multiprotein MLL1 and PRC2 complexes, respectively ( Figure 2C, middle and bottom panels).…”