Regulation of protein arginine methyltransferase 8 (PRMT8) activity by its N-terminal domain.
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.
Sayegh
Joyce
J
Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, California 90095-1569, USA.
Webb
Kristofor
K
Cheng
Donghang
D
Bedford
Mark T
MT
Clarke
Steven G
SG
D001665:Binding Sites / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008745:Methylation; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D011484:Protein-Arginine N-Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018909:src Homology Domains / Q000502:physiology
D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C099988:PRMT1 protein, human; C505447:PRMT8 protein, human; D011484:Protein-Arginine N-Methyltransferases