Exp Mol Med.  2004 Dec;36(6):563-571.

The nuclear 16-kD protein methylation increases in the early period of liver regeneration in a hepatectomized rat

• Lee K
• Lee KM
• Kim TJ
• Han JS
• Kim MK
• Hong YS
• Park GH
• Lee KW

Abstract

Methylation events play a critical role in various cellular processes including regulation of gene transcription and proliferation. We observed that methyltransferase activity underwent time-dependent changes in the cytosol of the rat hepatocytes upon partial hepatectomy. However, any change in the methylation of nuclear proteins is not clear during hepatocyte proliferation. The nuclear fraction possesses basal level of methyltransferase to catalyze methylation of several proteins ranging from 7 to 70 kD prior to any hepatecmony. The specific p16 (16 kD) band was transiently and heavily methylated post 1 day hepatectomy, and then became non- detectable, but not in the control liver. Methylation of p16 band was completely inhibited by exogenously added histones, particularly 2AS, 1, 2A and 2B subtypes. The methylated p16 protein remains stable in either acid or alkali- induced demethylation conditions, indicating that methylation is not likely to occur on isoaspartyl or C-terminal cysteinyl residues. Exogenous addition of non-hydrolyzable GTP caused a dose- dependent suppression of a p16 methylation suggesting that G-proteins might play a role as an endogenous methylation inhibitor in vivo. Taken together, we have identified the proliferation event associated-methylation of the nuclear p16 protein in the hepatocytes undergoing liver regeneration.

Keyword

histone; nuclear methyl acceptors; protein methylation; regenerating rat liver

MeSH Terms

Alkalies/pharmacology
Animals
Cell Proliferation
Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology
Hepatectomy
Hepatocytes/drug effects/*metabolism
Histones/pharmacology
Liver Regeneration/drug effects/*physiology
Methylation/drug effects
Nuclear Proteins/*metabolism
Rats
Research Support, Non-U.S. Gov't
Sodium Chloride/pharmacology