N-acetylglucosamine-dependent nuclear import of neoglycoproteins

Nuclear proteins bearing O-linked N-acetylglucosaminyl residues are involved in nuclear transport and in transcriptional processes. However, the role of glycosylation remains to be determined. It was proposed that glycosylation could be involved in macromolecular complex formation or in nuclear targeting. In the present study, we show that, in digitonin-permeabilized cells, BSA substituted with beta-di-N-acetylchitobioside (GlcNAc beta 4GlcNAc) is transported from the cytosol to the nucleus in a sugar dependent manner. The process is time and ATP dependent. Under the conditions used, the nuclear import of beta-di-N-acetyl-chitobios BSA, as it has also been previously shown for the nuclear import of alpha-glucosyl BSA (Duverger et al., J. Cell Sci., 108, 1325-1332, 1995) does not require the addition of a cytosolic extract, while the nuclear import of peptidic-NLS substituted BSA does require such an addition. These results suggest that GlcNAc can act as a nuclear localization signal.