Recombination regulation by transcription-induced cohesin dissociation in rDNA repeats

Organisms maintain ribosomal RNA gene repeats (rDNA) at stable copy numbers by recombination; the loss of repeats results in gene amplification. Here we report a mechanism of amplification regulation. We show that amplification is dependent on transcription from a noncoding bidirectional promoter (E-pro) within the rDNA spacer. E-pro transcription stimulates the dissociation of cohesin, a DNA binding protein complex that suppresses sister-chromatid-based changes in rDNA copy number. This transcription is regulated by the silencing gene, SIR2, and by copy number. Transcription-induced cohesin dissociation may be a general mechanism of recombination regulation.