Establishment of sister chromatid cohesion at the S. cerevisiae replication fork
Authors: Yuki Katou
Frank Uhlmann
Armelle Lengronne
Yutaka Kanoh
Karl-Peter Hopfner
John McIntyre
Katsuhiko Shirahige
Journal: Molecular Cell (2006)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: sister chromatid cohesion; replication forks; cohesin complex; Eco1; Ctf4
Affiliations: Chromosome Segregation Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom.

Abstract:  Two identical sister copies of eukaryotic chromosomes are synthesized during S phase. To facilitate their recognition as pairs for segregation in mitosis, sister chromatids are held together from their synthesis onward by the chromosomal cohesin complex. Replication fork progression is thought to be coupled to establishment of sister chromatid cohesion, facilitating identification of replication products, but evidence for this has remained circumstantial. Here we show that three proteins required for sister chromatid cohesion, Eco1, Ctf4, and Ctf18, are found at, and Ctf4 travels along chromosomes with, replication forks. The ring-shaped cohesin complex is loaded onto chromosomes before S phase in an ATP hydrolysis-dependent reaction. Cohesion establishment during DNA replication follows without further cohesin recruitment and without need for cohesin to re-engage an ATP hydrolysis motif that is critical for its initial DNA binding. This provides evidence for cohesion establishment in the context of replication forks and imposes constraints on the mechanism involved. 

Retracted: No

PubPeer comments:
 Readers should become aware of a preprint entitled  Scc2-mediated loading of cohesin onto chromosomes in G1 yeast cells is insufficient to build cohesion during S phase that challenge part of the conclusions obtained at Lengronne et al., 2006 paper https: www.biorxiv.org content 10.1101 123596v1 From the Abstract:  Sister chromatids are held together from their replication until mitosis. Sister chromatid cohesion is mediated by the ring-shaped cohesin complex and it is thought that cohesin holds sister chromatids together by entrapping sister DNAs within the cohesin ring (Haering et al., 2008). However, how this occurs is not well understood. Because cohesin binds to DNA prior to replication it is possible that the replication fork passes through the lumen of the ring thereby placing replicated sisters inside cohesin rings. If this is the case, loading of cohesin in the G1 phase may be sufficient to build cohesion. **We show here that Scc2, a cohesin subunit required for loading cohesin onto chromosomes de novo, is necessary for establishment of cohesion even after Scc2-mediated loading has already taken place during late G1 or early S phase. Our results challenge a previous conclusion based on related experiments whereby Scc2 was found not to be required for cohesion establishment during S phase (Lengronne et al., 2006). ** , 
 #1 Dear Chlorissa thanks for pointing out this misleading statement in the Nasmyth preprint. We showed in Lengronne et al. 2006 that Scc2 is no longer essential during S phase, following Scc2-dependent cohesin loading in G1. We inferred from this that cohesion establishment during S phase is possible without the need for additional cohesin loading. We have meanwhile extended these observation in Murayama et al. 2018. In this study, we characterize a biochemical pathway in which Scc2 promotes co-entrapment of two DNAs. We furthermore provide evidence that, in addition to the Scc2-independent pathway, Scc2-dependent cohesion establishment takes place at DNA replication forks in vivo. Based on these observations, we propose in Murayama et al. 2018 that two pathways for cohesion establishment cooperate during S phase. One that utilizes cohesin loaded in G1 and does not require Scc2, and one in which Scc2 promotes DNA co-entrapment during DNA replication. The Lengronne et al. 2006 conclusions are valid and form an important part of this model. It is unfortunate that Nasmyth portrays the findings in Lengronne et al. 2006 as a discrepancy, when indeed they contribute an important aspect of our current understanding of sister chromatid cohesion. Indeed, the data reported in the Nasmyth preprint are well compatible with those in Lengronne et al. 2006. Both studies demonstrate that the essential cohesion establishment factor Eco1 bears a greater role during S phase when compared to Scc2. While this important result is missed by Nasmyth, it is apparent from their cohesion timecourse experiments. Thus, the Nasmyth results corroborate our model in which Scc2 is part of one of two cohesion establishment pathways. I hope this clarifies the misunderstanding caused by an unfortunate choice of words. I am more than happy to discuss this further, in the interest of transparency preferably using any personally identifiable route of scholarly communication. Frank , 
 #2 Dear Prof. Uhlmann, As an outside observer, it seems to me that your response provides helpful nuance and context. You might want to consider posting it directly at bioRxiv as a comment on the Nasmyth preprint. Otherwise, readers who encounter the bioRxiv preprint will be unlikely to be aware of your response here. Separately, you might want to know that the original commenter has posted about numerous bioRxiv manuscripts on disparate subjects but with the commonality that they are tagged at bioRxiv as  Contradictory Results , and hence the comment does not necessarily reflect genuine interest in the topic per se. Some other recent examples: https: pubpeer.com publications 481532AF9790689C7A094B8137B096#1 https: pubpeer.com publications 5064084B249E84F0087D0E5238CB20#2 ,