EN
To study the behavior of newly synthesized RNA molecules during unperturbed mitosis and after induction of aneuploid nuclei, a novel method based on the incorporation of 5-ethynyl uridine was applied. This approach allows revealing transcription in cytological specimens by omitting immunocytochemical procedures. The obtained results indicate that RNAs synthesized in the preceding cell cycle behave similarly as nucleolar proteins and participate in post-mitotic nucleolar assembly not only during unperturbed nuclear divisions. Colocalization of nucleolar proteins and RNAs seems also to occur in aneuploid nuclei devoid of functional nucleolar organizer regions (NORs) or NOR per se. This paper also shows the presence of nucleoplasmic gene expression in aberrant aneuploid nuclei and micronuclei, despite occurrence of their genetic material disorganization. Moreover, experiments showing the effect of transcription and replication inhibition on the induction of aneuploid nuclei were also performed. Presented data shed new light on nucleologenesis and co-existence of nucleolar proteins with RNAs in prenucleolar bodies formed in aneuploid nuclei devoid of functional NORs.