Abstract
Cohesin is a multi-subunit protein complex essential for sister chromatid cohesion, gene expression and DNA damage repair. Although structurally well studied, the underlying determinant of cohesion establishment on chromosomal arms remains enigmatic. Here, we show two populations of functionally distinct cohesin on chromosomal arms using a combination of genomics and single-locus specific DNA-FISH analysis. Chromatin bound cohesin at the loading sites co-localizes with Pds5 and Eso1 resulting in stable cohesion. In contrast, cohesin independent of its loader is unable to maintain cohesion and associates with chromatin in a dynamic manner. Cohesive sites coincide with highly expressed genes and transcription inhibition leads to destabilization of cohesin on chromatin. Furthermore, induction of transcription results in de novo recruitment of cohesive cohesin. Our data suggest that transcription facilitates cohesin loading onto chromosomal arms and is a key determinant of cohesive sites in fission yeast.
Highlights
Cohesin is a conserved multi-subunit protein complex that plays an essential role in sister chromatid cohesion and proper chromosome segregation
structural maintenance of chromosomes (SMC) proteins are characterized by a globular hinge domain surrounded by two ␣-helices that fold back onto themselves at the hinge, thereby bringing the Nand C-termini together to form an ABC-type nucleotide binding domain (NBD) [3]
The multi-subunit cohesin complex is highly conserved across all eukaryotes and executes cohesion, transcription and repair/recombination functions [51]
Summary
Cohesin is a conserved multi-subunit protein complex that plays an essential role in sister chromatid cohesion and proper chromosome segregation. The core cohesin complex consists of structural maintenance of chromosomes (SMC) proteins, Psm and Psm, and the kleisin subunit Rad (Table 1) [1,2]. The SMC proteins form Vshaped Psm3-Psm heterodimers that interact with the Nand C-terminal domains of Rad, forming the tripartite cohesin ring [4]. The ring is further stabilized by the essential subunit Psc which is recruited by Rad21 [5]. Experimental evidence strongly suggests that cohesion is maintained via topological entrapment of sister chromatids by the cohesin ring [6,7]
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