Nuclear translocation of monoclonal antibody directed against cell-surface carbohydrate Y determinant.

Monoclonal antibody (MAb) Br 15-6A directed against the carbohydrate Y determinant expressed on tumor cells was found to be internalized and translocated to the nucleus of SK Br 5 breast carcinoma and SW 1116 and SW 707 colorectal carcinoma cells. Intracellular localization of MAb Br 15-6A was determined by cell fraction and by indirect immunofluorescence staining. Internalization of MAb Br 15-6A seems to be mediated by a specific cell surface protein of M(r) 108,000 in colorectal carcinoma cells and M(r) 92,000-96,000 in breast carcinoma cells. The MAb Br 15-6A precipitates an 88,000 M(r) chromatin protein and appears to be bound specifically to two EcoRI-digested and two HincII-chromatin fragments. Another MAb against the Y determinant (MAb Br 55.2) recognizes the same antigens as MAb Br 15-6A, but is not internalized.