Substrate-Induced Control of Product Formation by Protein Arginine Methyltransferase 1

Abstract

Protein arginine methyltransferases (PRMTs) aid in the regulation of many biological processes. Accurate control of PRMT activity includes recognition of specific arginyl groups within targeted proteins and the generation of the correct level of methylation, none of which are fully understood. The predominant PRMT in vivo, PRMT1, has wide substrate specificity and is capable of both mono- and dimethylation, which can induce distinct biological outputs. What regulates the specific methylation pattern of PRMT1 in vivo is unclear. We report that PRMT1 methylates a multisite peptide substrate in a nonstochastic manner, with less C-terminal preference, consistent with the methylation patterns observed in vivo. With a single targeted arginine, PRMT1 catalyzed the dimethylation in a semiprocessive manner. The degree of processivity is regulated by substrate sequences. Our results identify a novel substrate-induced mechanism for modulating PRMT1 product specificity. Considering the numerous physiological PRMT1 substrates, as well as the distinct biological outputs of mono- and dimethylation products, such fine-tuned regulation would significantly contribute to the accurate product specificity of PRMT1 in vivo and the proper transmission of biochemical information.

Structural insight into arginine methylation by the mouse protein arginine methyltransferase 7: a zinc finger freezes the mimic of the dimeric state into a single active site

“…As the methylated sites of PRMT substrates are usually located on flexible or unfolded terminal extensions, small conformational changes may be required to translocate the target peptide from one active site to the other. Whether PRMT-catalyzed dimethylation results from a distributive or a processive mechanism remains controversial and requires more structural and biochemical data (Osborne et al, 2007;Obianyo et al, 2008;Lakowski & Frankel, 2008;Kö lbel et al, 2009;Rust et al, 2011;Obianyo & Thompson, 2012;Antonysamy et al, 2012;Gui et al, 2013). This dynamic biological process involving specific protein recognition and a catalytic mechanism requiring the hydrolysis of two AdoMet molecules remains to be elucidated at the atomic level.…”

Chemical Biology of Protein Arginine Modifications in Epigenetic Regulation

“…126 By performing double-turnover reaction experiments, the Hevel group observed both MMA and ADMA formation, confirming a general semiprocessive mechanism of PRMT1 catalysis. 127 Interestingly, the proportions of MMA and ADMA generated are different among distinct peptide substrates. For example, the N-terminal H4 peptide SG R GKGGKGLGKGGAKR is preferentially processed through a processive mechanism, leading to a dimethylated product, while other sequences such as the fibrillarin-based RKK peptide GG R GGFGGKGGFGGKW partition more frequently through a distributive mechanism where both monomethylated and dimethylated products are ultimately generated.…”

“…These observations clearly indicate that the degree of processivity is controlled in a substrate-dependent manner and thus distinct patterns of methylation can be deposited by the same PRMT enzyme. 127 Thus, conflicting observations regarding the processive or distributive nature of PRMT1 activity may be partially due to the different substrates used and hence changes in the substrate-induced processivity rate. By contrast, recent data indicate that PRMT5 uses a distributive mechanism to catalyze the symmetric dimethylation of histone H4 and its N-terminal peptide fragment.…”

Protein Arginine Methyltransferase 5 Catalyzes Substrate Dimethylation in a Distributive Fashion

“…Hevel and colleagues have previously used this assay to show that PRMT1 uses a partially processive mechanism. 20 For the cPRMT5-catalyzed methylation of histone H4, the reaction mixtures contained 10 μM SAM, 10 μM histone H4, and 5 μM cPRMT5. For the hPRMT5·MEP50 complexcatalyzed reaction, mixtures contained 2 μM SAM, 10 μM histone H4, and 1 μM hPRMT5·MEP50 complex.…”