INTRANUCLEAR DISTRIBUTION OF GALECTIN-3 IN MOUSE 3T3 FIBROBLASTS - COMPARATIVE ANALYSES BY IMMUNOFLUORESCENCE AND IMMUNOELECTRON MICROSCOPY

The intracellular distribution of carbohydrate binding protein 35 (CBP 35), recently named galectin-3, was studied in mouse 3T3 fibroblasts, using immunofluorescence at the light microscope level and immunogold labeling at the ultrastructural level. In general, serum-stimulated, p roliferating cells showed higher levels of labeling than quiescent cul tures of the same cells, In the proliferating cells, the labeling inte nsity was higher in the nucleus than in the cytoplasm. Treatment of pe rmeabilized cells or thin sections with ribonuclease A decreased the i mmunolabeling intensity, whereas parallel control treatments with deox yribonuclease I failed to yield the same effect. While there appears t o be general agreement between the immunofluorescence and the ultrastr uctural results regarding the level of CBP35 and its association with nuclear ribonucleoprotein complexes, there was one striking difference in terms of labeling of specific subnuclear structures. Immunofluores cence results indicate diffuse distribution of CBP35 within the nucleu s, but the label appears to be excluded from certain ''black holes,'' which most probably correspond to nucleoli, On the other hand, immunog old particles were observed in electron microscopy, mainly in interchr omatin spaces, except for interchromatin granule clusters, at the bord er of condensed chromatin, on the dense fibrillar component, and at th e periphery of the fibrillar centers of nucleoli. (C) 1995 Academic Pr ess, Inc.