The structure of rDNA chromatin

Abstract

The nucleolus is the site of transcription of large tandem repeated arrays of the rDNA which carry the genes for three of the four ribosomal RNAs in eukaryotes. We describe the general genomic features of the rDNA and review what is currently known about its physical organization within the nucleolus. rDNA, like other parts of eukaryotic genomes, is complexed with histones and other proteins to form chromatin, which can adopt at least three functional states that are likely to correlate with physical organization. We review the current state of knowledge of the histones and non-histone proteins in nucleolar chromatin, highlighting both similarities and differences between nucleolar and nuclear chromatin fractions. © 2011 Springer Science+Business Media, LLC.