A monoclonal antibody against a family of nuclear pore proteins (nucleoporins): O-linked N-acetylglucosamine is part of the immunodeterminant.

Using nuclear envelopes from Chinese hamster ovary (CHO) cells as an antigen, a mouse monoclonal antibody (IgM; designated mAb CHON211) that specifically binds to components of the nuclear pore complex (nucleoporins) was isolated. Immunofluorescence localization of the antigen recognized by mAb CHON211 revealed a punctate pattern restricted to the nuclear envelope; this pattern changed dramatically during the cell cycle. When examined by electron microscopy, the antigen was largely restricted to the nucleoplasmic and cytoplasmic faces of the nuclear pore complex. Immunoblots showed that mAb CHON211 bound to a series of polypeptides enriched in the nuclear envelope fraction with apparent molecular masses ranging from 110 to 35 kDa. Using galactosyltransferase and the lectin wheat germ agglutinin as probes, we have previously shown that proteins bearing O-linked N-acetylglucosamine (GlcNAc) are restricted to the cytoplasmic and nucleoplasmic faces of the nuclear pore complex. The nuclear membrane proteins recognized by mAb CHON211 had properties very similar to those identified by galactosyltransferase and wheat germ agglutinin labeling. Removal of O-linked GlcNAc residues with beta-hexosaminidase greatly reduced the binding of mAb CHON211, strongly suggesting that O-linked GlcNAc moieties are part of the immunodeterminant. This monoclonal antibody defines a new family of antigens that are restricted to the nuclear pore and bear a common modification: O-linked GlcNAc. mAb CHON211 will be useful for defining the role of the nucleoporins in nucleo-cytoplasmic exchange.