An experimental approach to the study of ag-nor proteins

Purified polyclonal antibodies have been obtained against 100 KD and 36 KD Ag-NOR proteins. These two antibodies have been used to study the immunolocalization of both proteins on different cell types subjected to various conditions of cell activity and to observe a nucleolar labelling with anti-36 kDa Ag-NOR protein antibody evenly distributed over the dense fibrillar component and granular component, and with anti-100 kDa mainly localized to the dense fibrillar component. After actinomycin D treatment, immunolabelling with both antibodies was found restricted to the granular zone of segregated nucleoli. Moreover, to further study the functional role of these proteins, we have used an electroporation system to introduce both antibodies into the nuclei of living cells, and have clearly detected a different nucleolar behaviour. The combination of these techniques has been shown to be an important tool to deepen the knowledge of the nucleolus and has allowed us to propose that the difference in nucleolar localization of the major 36 kDa and 100 kDa Ag-NOR proteins is the consequence of a different role of both proteins in the synthesis and processing of rRNA