Pseudo-NORs: a novel model for studying nucleoli - PubMed (original) (raw)
Review
. 2008 Nov;1783(11):2116-23.
doi: 10.1016/j.bbamcr.2008.07.004. Epub 2008 Jul 18.
Affiliations
- PMID: 18687368
- DOI: 10.1016/j.bbamcr.2008.07.004
Free article
Review
Pseudo-NORs: a novel model for studying nucleoli
José-Luis Prieto et al. Biochim Biophys Acta. 2008 Nov.
Free article
Abstract
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.