Pseudo-NORs: a novel model for studying nucleoli

José-Luis Prieto, Brian McStay

    Research output: Contribution to journalArticlepeer-review

    44 Citations (Scopus)


    Nucleolar organiser regions (NORs) are comprised of tandem arrays of ribosomal gene (rDNA) repeats that are transcribed by RNA polymerase I (Pol I), ultimately resulting in formation of a nucleolus. Upstream binding factor (UBF), a DNA binding protein and component of the Pol I transcription machinery, binds extensively across the rDNA repeat in vivo. Pseudo-NORs are tandem arrays of a heterologous DNA sequence with high affinity for UBF introduced into human chromosomes. In this review we describe how analysis of pseudo-NORs has provided important insights into nucleolar formation. Pseudo-NORs mimic endogenous NORs in a number of important respects. On metaphase chromosomes both appear as secondary constrictions comprised of undercondensed chromatin. The transcriptional silence of pseudo-NORs provides a platform for studying the transcription independent recruitment of factors required for nucleolar formation by this specialised chromatin structure. During interphase, pseudo-NORs appear as distinct and novel sub-nuclear bodies. Analysis of these bodies and comparison to their endogenous counterpart has provided insights into nucleolar formation and structure.
    Original languageEnglish
    Pages (from-to)2116-23
    Number of pages8
    JournalBBA - General Subjects
    Issue number11
    Publication statusPublished - Nov 2008


    • Cell Cycle
    • Cell Nucleolus
    • Chromatin
    • Chromosomes, Human
    • DNA, Ribosomal
    • Humans
    • Nucleolus Organizer Region
    • Pol1 Transcription Initiation Complex Proteins
    • RNA Polymerase I
    • Transcription, Genetic


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