The loading of condensin in the context of chromatin

Abstract

The packaging of DNA into chromosomes is a ubiquitous process that enables living organisms to structure and transmit their genome accurately through cell divisions. In the three kingdoms of life, the architecture and dynamics of chromosomes rely upon ring-shaped SMC (Structural Maintenance of Chromosomes) condensin complexes. To understand how condensin rings organize chromosomes, it is essential to decipher how they associate with chromatin filaments. Here, we use recent evidence to discuss the role played by nucleosomes and transcription factors in the loading of condensin at transcribed genes. We propose a model whereby cis-acting features nestled in the promoters of active genes synergistically attract condensin rings and promote their association with DNA.

Cohesin dynamic association to chromatin and interfacing with replication forks in genome integrity maintenance

“…In this view, Cdc48 would target ubiquitylated cohesin and reshape its structure to favour the opening of a DNA exit gate and the release of the complex from DNA. Of note, a role for Cdc48 in mobilizing the SMC condensin complex to promote its dynamic interaction with chromatin was recently described (Robellet et al 2017;Thattikota et al 2018). Mutations in Rsp5 Bul2 and Cdc48 impairing cohesin mobilization confer sensitivity to replication stress inducing agents, which is genetically linked to cohesin function in replication fork protection (Frattini et al 2017) .…”

Limits of Chromosome Compaction by Loop-Extruding Motors

“…Alternatively, LEFs could be effectively two-sided if condensins avoid creating gaps by dimerizing or otherwise cooperating or interacting to form two-sided complexes. This case could occur if condensins tend to associate at specific loading sites, randomly distributed loading complexes, or adjacent to other bound condensins [82][83][84]. However, high specificity would be needed in order to obtain the approximately 40-fold reduction in gap frequency needed for 1000-fold compaction [56].…”

3D clustering of co-regulated genes and its effect on gene expression

“…For both GAL1 and MET3 reporters, the interaction becomes stronger under the activating condition, suggesting that the interactions may be mediated by transcription-related proteins or RNA transcripts. In fission yeast, it was proposed that condensin is used to connect actively transcribed genes (Iwasaki and Noma 2016; Robellet et al 2016). Third, genes at the cluster show higher expression.…”