Alterations of fibrillarin distribution and nucleolar ultrastructure induced by adenovirus infection

Nucleolar modifications induced by adenovirus type 5 (Ad5) have been examined in HeLa cells by bismuth staining and immunogold labeling of fibrillarin, both of which visualize the dense fibrillar component (DFC) of nucleoli. A progressive increase in the compaction of the nucleolus is accompanied both by a migration of strands of DFC towards the border of the nucleolar body and by a decrease in the amount of fibrillarin within the bismuth stained DFC. In addition, the bismuth-stained extranucleolar fibrillar spots induced by Ad5 infection often were intensely labeled with monoclonal anti-fibrillarin antibody. Previously reported defects in ribosomal RNA expression during adenovirus infection could result from the migration and accumulation of nucleolar proteins implicated in ribosomal biogenesis into virus-induced extranucleolar structures.