ARE THERE GOLGI-TYPE GLYCANS IN THE NUCLEOCYTOPLASMIC COMPARTMENT?
There are several possible explanations for the potential origins of complex nucleocytoplasmic glycans suggested by cytological studies, as summarized in Figure 17.1. Most simply, nonconventional soluble glycosyltransferases may reside in the cytoplasm or nucleus and directly modify proteins there (Figure 17.1a). Nucleotide sugar precursors are available, because the enzymes that synthesize them reside within these compartments. As discussed below, this is the mechanism by which glycogen synthesis is primed and by which Skp1 is modified by multiple sugar types in the cytoplasm of Dictyostelium. Glycosylated proteins might then be transferred to the nucleus through nuclear pores via conventional nuclear transport pathways.
