The acetylation level of rDNA in Brassica campestris

Ribosomal DNA is an important repeated sequence that forms the nucleolus at the interphase. Its transcription into ribosomal RNA for ribosome biogenesis also represents a transitional point for several cellular processes, including cell-cycle progression, gene-silencing, and formation of the ribonucleoprotein complex. The levels of rDNA acetylation have an important role in regulating structural changes in rDNA chromatin and transcriptional activity. Using root-tip samples from Brassica campestris, we determined that some rDNA chromatin is located in the heterochromatin regions while some is de-condensed and found in euchromatin regions. Immuno-staining results showed that histone H4K5 acetylation and H4 tetra-acetylation signals are dispersed within the euchromatin. Analysis of the promoter and exon regions of rDNA via chromatin immuno-precipitation (ChIP) revealed a connection between histone acetylation and rDNA conformation.