Recent advances in protein methylation: Enzymatic methylation of nucleic acid binding proteins

초록

Heterogeneous nuclear RNP protein Al, one of the major proteins in hnRNP particle (precursor for mRNA),is known to be posttranslationally arginine-methylated in vivo on residues 193, 205, 217 and 224 within the RGG box, the motif postulated to be an RNA binding domain. Possible effect of N-G-arginine methyl-modification in the interaction of protein Al to nucleic acid was investigated. The recombinant hnRNP protein Al was in vitro methylated by the purified nuclear protein/histone-specific protein methylase I (S-adenosylmethionine:protein-arginine N-methyltransferase) stoichiometrically and the relative binding affinity of the methylated and the unmethylated protein Al to nucleic acid was compared: Differences in their binding properties to ssDNA-cellulose, pi values and trypsin sensitivities in the presence and absence of MS2-RNA all indicate that the binding property of hnRNP protein Al to single-stranded nucleic acid has been significantly reduced subsequent to the methylation. These results suggest that posttranslational methyl group insertion to the arginine residue reduces protein-RNA interaction, perhaps due to interference of I-I-bonding between guanidino nitrogen arginine and phosphate RNA.

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