FIGURE 9.

A model representing mechanistic link between H3K9me2 and nucleolus fission via the accumulation of R-loops at the rDNA regions. The transient R-loop formed in the transcriptional process is hydrolyzed by RNase H1, leading to complementation of template strand DNA and antisense strand. However, in the presence of RNA polymerase I transcription inhibitors or the epigenetic inhibitor BIX, the level of H3K9me2 decreases significantly, which leads to the augmentation of rDNA transcription initiation and R-loop accumulation, resulting in a structurally disorganized nucleolus.