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Condensin loop extrusion properties, roadblocks, and role in homology search in S. cerevisiae

ABSTRACT: The in vivo mechanism, regulations by cis-acting roadblocks, and biological functions of loop extrusion by eukaryotic SMC complexes are incompletely defined. Here, using Hi-C, we identified two condensin-dependent contact stripes at the Recombination Enhancer (RE) and the rDNA in S. cerevisiae. We show that oriented, unidirectional loop extrusion proceeds from these sites with an estimated processivity ~170 kb and a density ~0.04-0.18 that varies across the cell cycle. Centromeres and highly-transcribed RNA PolII-dependent genes are permeable condensin roadblocks. Other positionally labile elements such as replication forks and Smc5/6 complexes bound to substrates generated in the absence of Top2 also hinder loop extrusion by condensin. Cohesin is not an obstacle for condensin. Finally, a DNA double-strand break at MAT blocks condensin, which results in the rapid establishment of a long-range RE-MAT loop that juxtaposes the recombination machinery with its HML donor target. Hence, all budding yeast SMCs are involved in recombinational DNA repair. We propose a revised model for donor selection during MAT switching that exploits specific properties of loop extrusion by condensin. It can serve as a paradigm for the establishment of other types of selective interactions along chromosomes.

ORGANISM(S): Saccharomyces cerevisiae W303 Saccharomyces cerevisiae

PROVIDER: GSE278899 | GEO | 2026/02/16

REPOSITORIES: GEO

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			Action	DRS
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	GSE278899_AD218_S288c_DSB_chr3_rDNA_parasplit_q20_v324_1kb.cool.gz	Other
	GSE278899_AD265_S288c_DSB_chr3_rDNA_cutsite_q20_v312_1kb.cool.gz	Other
	GSE278899_AD266_S288c_DSB_chr3_rDNA_cutsite_q20_v312_1kb.cool.gz	Other
	GSE278899_AD280_S288c_DSB_chr3_rDNA_cutsite_q20_v312_1kb.cool.gz	Other

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