Chromosome-refolding model of mating-type switching in yeast

Significance Although many studies have shown that chromosomes are folded into cells in a nonrandom fashion, the functional significance of this spatial organization remains poorly understood. Combining theory and fluorescence microscopy, we demonstrate that the folded state of yeast chromosome III changes in response to a DNA double-strand break at the MAT locus, in agreement with previous studies. Importantly, we show that the change in the folded state of the chromosome after the break quantitatively accounts for the dynamics of homology search during DNA repair. Our study provides an example of a cell changing the folded state of one of its chromosomes in response to an internal chemical cue (DNA break), thereby affecting its function (DNA repair).