Recombination Regulation by Transcription-Induced Cohesin Dissociation in rDNA Repeats

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Science  02 Sep 2005:
Vol. 309, Issue 5740, pp. 1581-1584
DOI: 10.1126/science.1116102

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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.

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