Fig. 2.

The RENT complex, recruitment to the rDNA and rDNA stability in yeast aging. A) The RENT complex consists of Sir2, Net1, and Cdc14, and functions as a histone H3 and H4 deacetylase within the nucleolus. B) RENT is recruited to the intergenic spacers of the rDNA repeats at either IGS1 via interactions with Fob1, or at IGS2 via interactions with RNA polymerase I at the rDNA gene promoter (Pol I). C) The rDNA genes are organized as a large tandem array on the right arm of chromosome XII. Double-strand DNA breaks that occur at the replication fork block site in IGS1 (red x) are repaired through homologous recombination. In the absence of SIR2, the rDNA tandem array is destabilized and unequal intra-chromatid exchange results in the formation of extrachromosomal rDNA circles (ERCs), which are self-replicating and asymmetrically segregated into mother cells.