Identification of highly methylated arginine residues in an endogenous 20-kDa polypeptide in cancer cells.
Enzymatic methylation of endogenous proteins in several cancer cell lines was investigated to understand a possible relationship between protein-arginine methylation and cellular proliferation. Cytosolic extracts prepared from several cancer cells (HeLa, HCT-48, A549, and HepG2) and incubated with S-adenosyl-L-[methyl-3H]methionine revealed an intensely [methyl-3H]-labeled 20-kDa polypeptide. On the other hand, cytosolic extracts prepared from normal colon cells did not show any methylation of the 20-kDa protein under identical conditions. To identify nature of the 20-kDa polypeptide, purified histones were methylated with HCT-48 cytosolic extracts and analyzed by SDS-PAGE. However, none of the histones comigrated with the methylated 20-kDa polypeptide, indicating that it is unlikely to be any of the histone subclasses. The [methyl-3H]group in the 20-kDa polypeptide was stable at pH 10-11 (37 degrees C for 30 min) and methylation was not stimulated by GTPgammaS (4 mM), thus the reaction is neither carboxyl methylesterification on isoaspartyl residues, nor on C-terminal farnesylated cysteine. The present study together with the previous identification of N(G)-methylated arginine residues in the HCT-48 cytosol fraction suggests that this novel endogenous 20-kDa arginine-methylation is a cellular proliferation-related posttranslational modification reaction.
Gu
H
H
Department of Biochemistry, Medical School, Korea University, Seoul.
Park
S H
SH
Park
G H
GH
Lim
I K
IK
Lee
H W
HW
Paik
W K
WK
Kim
S
S
D000818:Animals; D002457:Cell Extracts / Q000737:chemistry; D002471:Cell Transformation, Neoplastic / Q000737:chemistry; D006367:HeLa Cells / Q000737:chemistry; D006801:Humans; D008745:Methylation; D009363:Neoplasm Proteins / Q000737:chemistry*; D011484:Protein-Arginine N-Methyltransferases / Q000032:analysis*; D014316:Tritium; D014407:Tumor Cells, Cultured / Q000737:chemistry* / Q000166:cytology
D002457:Cell Extracts; D009363:Neoplasm Proteins; D014316:Tritium; D011484:Protein-Arginine N-Methyltransferases