title: Enzymatic methylation of heterogeneous nuclear ribonucleoprotein in isolated liver nuclei.
abstract: Protein N-methyltransferase activity has been studied in the rat liver nuclei, using recombinant heterogeneous nuclear ribonucleoprotein particle protein A1 and histone as the methyl acceptors. The hydrolysates of these two enzymatically [methyl-3H]-labeled proteins, however, yielded different patterns of methylated amino acids on HPLC analysis: NG-monomethylarginine (92%) and NG-NG-dimethyl (asymmetric) arginine (6.5%) were the major methylated amino acids identified in the protein A1, whereas epsilon-N-methylated lysine derivatives constituted a predominant portion (71%) of the methylated amino acids in histone. When liver extracts isolated from rats fed a methyl deficient diet were assayed, the methyl accepting activity of protein A1 increased 64% over the control (rats fed normal diet), while that of histone increased 260%. Partial hepatectomy induced a 7.9-fold and 2.3-fold increase in the protein A1 methylase activity after 24 and 48 h of regeneration, respectively. These results, together with the fact that myelin basic protein-specific protein methylase I does not significantly methylate protein A1, indicate the presence of an enzyme in the rat liver nuclei which methylates the protein A1.
authors.affiliation: Fels Institute for Cancer Research and Molecular Biology, Temple University, School of Medicine, Philadelphia, PA 19140.
authors.forename: R
authors.initials: R
authors.lastname: Rajpurohit
authors.forename: W K
authors.initials: WK
authors.lastname: Paik
authors.forename: S
authors.initials: S
authors.lastname: Kim
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D006498:Hepatectomy; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D008099:Liver / Q000201:enzymology*; D008297:Male; D011484:Protein-Arginine N-Methyltransferases / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D012261:Ribonucleoproteins / Q000378:metabolism*
chemical_list: D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D012261:Ribonucleoproteins; D011484:Protein-Arginine N-Methyltransferases