Methylation Site of Delta Antigen

Li et al. demonstrated that the methylation of S-HDAg could be catalyzed specifically by PRMT1 and the residue R13 of S-HDAg is essential for methylation in vitro.

PRMT1 has been found to catalyze methylation on arginine residues in RGG, RXR and GAR motifs of RNA-binding proteins (Boisvert et al. 2003; Wada et al. 2002). SHDAg contains two RGG motifs, 10-RGG-12 and 91-RGG-93. S-HDAg containing alanine substitution mutations of arginine 10 and arginine 91 could still be methylated in vitro, although mutation of arginine 10 reduced the intensity of S-HDAg methylation. However, arginine 13, which is adjacent to the 10-RGG-12 motif, appeared to be important for methylation to occur. Mutation of arginine 13 to alanine abolished methylation. Further study such as MASS analysis of purified cellular SHDAg might be necessary to verify methylation on the candidate R13 and other unidentified sites including arginine as well as lysine residues.

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