Potential regulation of nuclear UDP-N-acetylglucosaminyl transferase (OGT) by substrate availability: ability of chromatin protein to bind UDP-N-acetylglucosamine and reduce OGT-mediated O-Linked glycosylation.
UDP-N-acetylglucosaminyl transferase (OGT) resides in both cytosolic and nuclear compartments and catalyzes O-linked glycosylation of various proteins. In the current study, we have extracted protein from nuclear DNA (chromatin protein) using 0.2% NP-40 detergent. Addition of chromatin protein to either cytosolic or nuclear preparations (containing abundant OGT) resulted in a dose-dependent loss of OGT activity. Since chromatin-mediated loss of OGT activity could be restored by immunopurification of OGT, we conclude that loss of enzyme activity is not due to direct inactivation of OGT. Addition of UDP-galactose (to saturate potential UDP binding proteins) effectively restored OGT activity in cytosol containing chromatin protein. This indicates that chromatin protein inhibits OGT activity by binding UDP-GlcNAc. These studies suggest that nuclear substrate availability may comprise one of the in vivo mechanisms regulating OGT activity and O-linked glycosylation of nuclear proteins. This is potentially significant, since most transcription factors are O-linked glycosylated and such post-translational modifications can alter gene expression.
Okuyama
Ryo
R
Hexos, Inc, Woodinville, Washington 98072, USA. ryooku@sankyo.co.jp
Marshall
Stephen
S
D000117:Acetylglucosamine / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D006031:Glycosylation; D017351:N-Acetylglucosaminyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D013379:Substrate Specificity
D017351:N-Acetylglucosaminyltransferases; C037649:N-acetyllactosaminide beta-1,6-N-acetylglucosaminyltransferase; D000117:Acetylglucosamine