Regulation of Protein Arginine Methyltransferase 8 (PRMT8) Activity by Its N-terminal Domain

Abstract

Human protein arginine methyltransferase PRMT8 has been recently described as a type I enzyme in brain that is localized to the plasma membrane by N-terminal myristoylation. The amino acid sequence of human PRMT8 is almost 80% identical to human PRMT1, the major protein arginine methyltransferase activity in mammalian cells. However, the activity of a recombinant PRMT8 GST fusion protein toward methyl-accepting substrates is much lower than that of a GST fusion of PRMT1. We show here that both His-tagged and GST fusion species lacking the initial 60 amino acid residues of PRMT8 have enhanced enzymatic activity, suggesting that the N-terminal domain may regulate PRMT8 activity. This conclusion is supported by limited proteolysis experiments showing an increase in the activity of the digested full-length protein, consistent with the loss of the N-terminal domain. In contrast, the activity of the N-terminal truncated protein was slightly diminished by limited proteolysis. Significantly, we detect automethylation at two sites in the N-terminal domain, as well as binding sites for SH3 domain-containing proteins. We suggest that the N-terminal domain may function as an autoregulator that may be displaced by interaction with one or more physiological inducers.

Lysine methylation of VCP by a member of a novel human protein methyltransferase family

“…Unlike VCP-KMT, METTL21A-C and METTL23 failed to show MTase activity towards histones, amino-acid homopolymers or VCP. Some protein MTases display automethylation activity, and then with an amino-acid specificity identical to that observed for bona fide substrates [22][23][24] . Indeed, we detected significant automethylation in the case of METTL21A, METTL21C and VCP-KMT (Fig.…”

Mammalian Protein Arginine Methyltransferase 7 (PRMT7) Specifically Targets RXR Sites in Lysine- and Arginine-rich Regions

“…Thus, the singly methylated species was actually a mixture of peptides Table 1) were methylated by PRMT7 as described in Fig. 3 legend. A-H show PRMT7-catalyzed methylation products of H2B (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37) with monomethylation on different arginine residues, and Arg-29 and Arg-31 should be the major methylation sites on H2B. Additionally, the fragmentation pattern for the methylated H2B(23-37)R29K peptide is more consistent with the Arg-31 site of methylation (Fig.…”

“…Fig. 9A shows an example of the 5-charge state of H2B (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37) with an m/z of 388.03, which was deconvoluted to the monoisotopic mass of the peptide (1935.12 Da). After the reaction was catalyzed by PRMT7, Fig.…”

Proteomic Analysis of Arginine Methylation Sites in Human Cells Reveals Dynamic Regulation During Transcriptional Arrest

“…The extent of PRMT6 auto-methylation has not been fully elucidated; however, our data infers that PRMT6 could contain several N-terminal auto-methylation sites (R29, R35, and R37). As the N-terminal regions of other PRMTs previously have been demonstrated to modulate substrate binding specificity and methyltransferase enzymatic activity (41), these MMA sites may function as an autoregulatory mechanism for PRMT6. In support of this, one of the identified sites (R35) was recently confirmed as an auto-methylation site of PRMT6 affecting its methylase activity (42).…”