Scc2 Is a Potent Activator of Cohesin’s ATPase that Promotes Loading by Binding Scc1 without Pds5

Abstract

SummaryCohesin organizes DNA into chromatids, regulates enhancer-promoter interactions, and confers sister chromatid cohesion. Its association with chromosomes is regulated by hook-shaped HEAT repeat proteins that bind Scc1, namely Scc3, Pds5, and Scc2. Unlike Pds5, Scc2 is not a stable cohesin constituent but, as shown here, transiently replaces Pds5. Scc1 mutations that compromise its interaction with Scc2 adversely affect cohesin’s ATPase activity and loading. Moreover, Scc2 mutations that alter how the ATPase responds to DNA abolish loading despite cohesin’s initial association with loading sites. Lastly, Scc2 mutations that permit loading in the absence of Scc4 increase Scc2’s association with chromosomal cohesin and reduce that of Pds5. We suggest that cohesin switches between two states: one with Pds5 bound that is unable to hydrolyze ATP efficiently but is capable of release from chromosomes and another in which Scc2 replaces Pds5 and stimulates ATP hydrolysis necessary for loading and translocation from loading sites.

FACT mediates cohesin function on chromatin

“…2b). Mcd1 is expressed at low levels in G1-arrested cells, thus cohesin association to pericentric regions is very modest at this stage of the cell cycle 15 . However, cohesin loading can still occur in G1 26 when cohesin expression is artificially induced.…”

“…We first sought to analyse if nucleosomal occupancy is dynamic at sites of cohesin binding. In Saccharomyces cerevisiae CEN sequences are cohesin loading sites where complexes initially access chromosomes before spreading towards pericentric regions [12][13][14][15] . Genome-wide MNase-seq maps were generated 16 in G1 and G2/M arrests to analyse nucleosome occupancy around centromeric regions ( Fig.…”

“…2a). Centromeric regions are ideal sites to study cohesin translocation because cohesin complexes are initially loaded at core CEN sequences and then move away towards pericentromeric regions 15 . We observed that cohesin localisation to core CEN sequence did not change upon Spt16 degradation, however its accumulation at pericentric regions was severely reduced ( Fig.…”

“…In yeast, cohesin complexes can be divided into two classes with respect to their chromosomal association mechanisms, those loaded at CEN sequences, which move and accumulate in pericentric regions 28,29 , and those that load at chromosomal arm sites and translocate to regions of convergent transcription 30 . Importantly, the translocation of cohesins from CEN sites to pericentromeric regions requires Scc2 15 and is independent of transcription 15 , while the movement of arm loaded cohesins to sites between convergent genes involves relocation dependent on transcription [30][31][32][33] .…”

DNA entry, exit and second DNA capture by cohesin: insights from biochemical experiments

“…Both Pds5 and Scc2 interact with the flexible middle domain of Scc1. Although their interaction motifs on Scc1 are different, these sites are located in close proximity to each other [27,41]. Interestingly, purified Pds5 competes with Mis4 Scc2 -Ssl3 Scc4 for cohesin binding, suggesting that Scc2 and Pds5 bind to Scc1 in a mutually exclusive manner [37].…”