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Title: Human acrocentric chromosomes with transcriptionally silent nucleolar organizer regions associate with nucleoli
Authors: Sullivan, GJ
Bridger, JM
Cuthbert, AP
Newbold, RF
Bickmore, WA
McStay, B
Keywords: Animals;Cell Line;Cell Nucleus/genetics/ultrastructure;Chromosomes, Human/*genetics/ultrastructure;DNA, Ribosomal/*genetics;Fluorescent Antibody Technique;*Gene Silencing;Hela Cells;Humans;Hybrid Cells
Issue Date: 2001
Publisher: Nature Publishing Group
Citation: European Molecular Biology Organization. 20 (11) 2867-2874
Abstract: Human ribosomal gene repeats are distributed among five nucleolar organizer regions (NORs) on the p arms of acrocentric chromosomes. On exit from mitosis, nucleoli form around individual active NORs. As cells progress through the cycle, these mini-nucleoli fuse to form large nucleoli incorporating multiple NORs. It is generally assumed that nucleolar incorporation of individual NORs is dependent on ribosomal gene transcription. To test this assumption, we determined the nuclear location of individual human acrocentric chromosomes, and their associated NORs, in mouse> human cell hybrids. Human ribosomal genes are transcriptionally silent in this context. Combined immunofluorescence and in situ hybridization (immuno-FISH) on three-dimensional preserved nuclei showed that human acrocentric chromosomes associate with hybrid cell nucleoli. Analysis of purified nucleoli demonstrated that human and mouse NORs are equally likely to be within a hybrid cell nucleolus. This is supported further by the observation that murine upstream binding factor can associate with human NORs. Incorporation of silent NORs into mature nucleoli raises interesting issues concerning the maintenance of the activity status of individual NORs.
Appears in Collections:Biological Sciences
Dept of Life Sciences Research Papers

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