title: A role for upstream binding factor in organizing ribosomal gene chromatin.
abstract: Human ribosomal genes are located in NORs (nucleolar organizer regions) on the short arms of acrocentric chromosomes. During metaphase, previously active NORs appear as prominent chromosomal features termed secondary constrictions, which are achromatic in chromosome banding and positive in silver staining. The architectural RNA polymerase I transcription factor UBF (upstream binding factor) binds extensively across the ribosomal gene repeat throughout the cell cycle. Evidence that UBF underpins NOR structure is provided by an examination of cell lines in which large arrays of a heterologous UBF binding sequences are integrated at ectopic sites on human chromosomes. These arrays efficiently recruit UBF even to sites outside the nucleolus, and during metaphase form novel silver-stainable secondary constrictions, termed pseudo-NORs, that are morphologically similar to NORs.
authors.affiliation: Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Wright
authors.forename: Christine
authors.initials: C
authors.lastname: Mais
authors.forename: José-Luis
authors.initials: JL
authors.lastname: Prieto
authors.forename: Brian
authors.initials: B
authors.lastname: McStay
mesh_terms: D001665:Binding Sites / Q000235:genetics; D002843:Chromatin / Q000235:genetics* / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009697:Nucleolus Organizer Region / Q000235:genetics* / Q000378:metabolism*; D035463:Pol1 Transcription Initiation Complex Proteins / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding; D012270:Ribosomes / Q000235:genetics* / Q000378:metabolism*
chemical_list: D002843:Chromatin; D004275:DNA, Ribosomal; D035463:Pol1 Transcription Initiation Complex Proteins; C063844:transcription factor UBF