title: Experimental induction of prenucleolar bodies (PNBs) in interphase cells: interphase PNBs show similar characteristics as those typically observed at telophase of mitosis in untreated cells.
abstract: Recently, it was shown that a short exposure of living mammalian cells to low ionic strength buffers (hypotonic shock) caused partial or almost complete unraveling of interphase nucleoli. However, when the cells were released from the hypotonic shock and transferred to normal isotonic medium, functionally active and structurally integral nucleoli were reassembled at their initial positions within interphase nuclei. Here, we show further that this process is accompanied by the appearance of numerous discrete extranucleolar bodies, which have striking similarities to the prenucleolar bodies (PNBs) observed in untreated cells at telophase of mitosis. (1) Like PNBs at mitosis, hypotonically induced interphase PNBs are composed of RNA-positive granules and fibrils, contain the major nucleolar protein B23 and silver-binding proteins, but lack DNA and RNA polymerase I transcription factor UBF. (2) As for mitotic PNBs, disappearance of the interphase PNB counterparts coincides with the increase in size of reconstructed nucleoli. (3) Addition of actinomycin D does not prevent assembly of interphase PNBs, but does arrest their coalescence with the chromosomal nucleolus-organizing regions and blocks the complete reformation of nucleoli. It is concluded that the assembly of PNBs generally observed at telophase of mitosis can be induced experimentally in nuclei of interphase mammalian cells in vivo. At interphase, this process is probably initiated by changes in the intracellular ionic environment.
authors.affiliation: A.N. Belozersky Institute of Physical and Chemical Biology, Moscow State University, Moscow 119899, Russia.
authors.forename: O V
authors.initials: OV
authors.lastname: Zatsepina
authors.forename: O A
authors.initials: OA
authors.lastname: Dudnic
authors.forename: I T
authors.initials: IT
authors.lastname: Todorov
authors.forename: M
authors.initials: M
authors.lastname: Thiry
authors.forename: H
authors.initials: H
authors.lastname: Spring
authors.forename: M F
authors.initials: MF
authors.lastname: Trendelenburg
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D002478:Cells, Cultured; D003470:Culture Media / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000276:immunology / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D006367:HeLa Cells / Q000187:drug effects; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D015151:Immunoblotting; D007150:Immunohistochemistry; D007399:Interphase / Q000502:physiology*; D008853:Microscopy; D008854:Microscopy, Electron; D008938:Mitosis / Q000502:physiology*; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D009994:Osmolar Concentration; D035463:Pol1 Transcription Initiation Complex Proteins; D012335:RNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D013692:Telophase / Q000187:drug effects / Q000502:physiology*; D014157:Transcription Factors / Q000276:immunology / Q000378:metabolism
chemical_list: D003470:Culture Media; D004268:DNA-Binding Proteins; D007038:Hypotonic Solutions; D009687:Nuclear Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D035463:Pol1 Transcription Initiation Complex Proteins; D012335:RNA, Ribosomal; D014157:Transcription Factors; C063844:transcription factor UBF; D003609:Dactinomycin