The RNA polymerase I transcription factor UBF and rDNA are located at the same major sites in both interphase and mitotic pig embryonic kidney (PK) cells

• Published in: Cytogenetics and cell genetics Vol. 73; no. 4; pp. 274 - 278
• Main Authors: ZATSEPINA, O. V, SCHÖFER, C, WEIPOLTSHAMMER, K, MOSGEOLLER, W, ALMEDER, M, STEFANOVA, V. N, JORDAN, E. G, WACHTLER, F
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Freiburg Karger 01.01.1996; Basel; Paris
• Subjects: Animals; Cell Cycle; Cell Line; Cell Nucleolus - chemistry; Cell Nucleolus - ultrastructure; DNA, Ribosomal - analysis; DNA-Binding Proteins - analysis; Embryo, Mammalian; In Situ Hybridization, Fluorescence; Interphase; Kidney - chemistry; Kidney - cytology; Microscopy, Confocal; Mitosis; Nucleolus Organizer Region - chemistry; Nucleolus Organizer Region - ultrastructure; Pol1 Transcription Initiation Complex Proteins; RNA Polymerase I - metabolism; Silver Staining; Swine; Transcription Factors - analysis
• ISSN: 0301-0171
• DOI: 10.1159/000134354

Indirect immunolabeling with anti-UBF antibodies, in situ hybridization with an rDNA probe, and confocal scanning laser microscopy were used to study nucleolar organizer regions (NORs) during the cell cycle in pig embryonic kidney (PK) cells. The chromosomal distribution of the polymerase I transcription factor UBF and rDNA was compared with the number of silver-stained NORs (Ag-NORs) present and nucleolar size. It was shown, both at interphase and mitosis, that the majority of UBF and rDNA signals were located at the same foci and that the amounts of UBF and rDNA at any given site were in a striking positive correlation. At mitosis, only the NORs were labeled; at interphase, the signals for both UBF and rDNA were arranged in necklace-like structures around the nucleoli. No chromosomal NORs without Ag-proteins or UBF were present, indicating that all NORs in PK cells are active at interphase. It was concluded that (1) UBF and rDNA co-localize throughout the cell cycle in PK cells; (2) their association with mitotic NORs is determined by the number of rDNA repeats, rather than by any differential ability of NORs to recruit the transcription factor; and (3) the amount of UBF can be correlated with the size and activity of the nucleoli at interphase.