Construction of synthetic nucleoli in human cells reveals how a major functional nuclear domain is formed and propagated through cell division.
Human cell nuclei are functionally organized into structurally stable yet dynamic bodies whose cell cycle inheritance is poorly understood. Here, we investigate the biogenesis and propagation of nucleoli, sites of ribosome biogenesis and key regulators of cellular growth. Nucleolar and cell cycles are intimately connected. Nucleoli disappear during mitosis, reforming around prominent uncharacterized chromosomal features, nucleolar organizer regions (NORs). By examining the effects of UBF depletion on both endogenous NORs and synthetic pseudo-NORs, we reveal its essential role in maintaining competency and establishing a bookmark on mitotic NORs. Furthermore, we demonstrate that neo-NORs, UBF-binding site arrays coupled with rDNA transcription units, direct the de novo biogenesis of functional compartmentalized neonucleoli irrespective of their site of chromosomal integration. For the first time, we establish the sequence requirements for nucleolar biogenesis and provide proof that this is a staged process where UBF-dependent mitotic bookmarking precedes function-dependent nucleolar assembly.
Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Ireland.
Alice
A
Grob
Christine
C
Colleran
Brian
B
McStay
D016475:3T3 Cells; D000818:Animals; D058045:Artificial Cells / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology*; D002466:Cell Nucleolus / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008938:Mitosis / Q000502:physiology; D009697:Nucleolus Organizer Region / Q000235:genetics / Q000378:metabolism; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism
D035463:Pol1 Transcription Initiation Complex Proteins; D012335:RNA, Ribosomal; C063844:transcription factor UBF
UBF; mitotic bookmarking; neo-NOR; nucleolar organizer region (NOR); nucleolus; pseudo-NOR