Glycosylation of nucleocytoplasmic proteins: Signal transduction and O-GlcNAc

The dynamic glycosylation of serine or threonine residues on nuclear and cy tosolic proteins by O-Linked beta -N-acetylglucosamine (O-GLcNAc) is abunda nt in all multicellular eukaryotes, On several proteins, O-GLcNAc and O-pho sphate alternatively occupy the same or adjacent sites, Leading to the hypo thesis that one function of this saccharide is to transiently block phospho rylation, The diversity of proteins modified by O-GlcNAc implies its import ance in many basic cellular and disease processes. Here we systematically e xamine the current data implicating O-GlcNAc as a regulatory modification i mportant to signal transduction cascades.