scholarly journals Towards a Structural Mechanism for Sister Chromatid Cohesion Establishment at the Eukaryotic Replication Fork

Biology ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 466
Author(s):  
Sarah S. Henrikus ◽  
Alessandro Costa
Keyword(s):  
Single Molecule ◽  
Sister Chromatid ◽  
Replication Fork ◽  
Genetic Material ◽  
Sister Chromatid Cohesion ◽  
Duplex Dna ◽  
Structural Mechanism ◽  
Chromatin Dynamics ◽  
Chromatid Cohesion ◽  
Replication Factors

Cohesion between replicated chromosomes is essential for chromatin dynamics and equal segregation of duplicated genetic material. In the G1 phase, the ring-shaped cohesin complex is loaded onto duplex DNA, enriching at replication start sites, or “origins”. During the same phase of the cell cycle, and also at the origin sites, two MCM helicases are loaded as symmetric double hexamers around duplex DNA. During the S phase, and through the action of replication factors, cohesin switches from encircling one parental duplex DNA to topologically enclosing the two duplicated DNA filaments, which are known as sister chromatids. Despite its vital importance, the structural mechanism leading to sister chromatid cohesion establishment at the replication fork is mostly elusive. Here we review the current understanding of the molecular interactions between the replication machinery and cohesin, which support sister chromatid cohesion establishment and cohesin function. In particular, we discuss how cryo-EM is shedding light on the mechanisms of DNA replication and cohesin loading processes. We further expound how frontier cryo-EM approaches, combined with biochemistry and single-molecule fluorescence assays, can lead to understanding the molecular basis of sister chromatid cohesion establishment at the replication fork.

scholarly journals Interaction of the Warsaw breakage syndrome DNA helicase DDX11 with the replication fork-protection factor Timeless promotes sister chromatid cohesion

PLoS Genetics ◽  
2018 ◽  
Vol 14 (10) ◽  
pp. e1007622 ◽  
Author(s):  
Giuseppe Cortone ◽  
Ge Zheng ◽  
Pasquale Pensieri ◽  
Viviana Chiappetta ◽  
Rosarita Tatè ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Replication Fork ◽  
Dna Helicase ◽  
Sister Chromatid Cohesion ◽  
Protection Factor ◽  
Chromatid Cohesion

scholarly journals Scc2/Nipbl hops between chromosomal cohesin rings after loading

2017 ◽  
Author(s):  
James D.P. Rhodes ◽  
Davide Mazza ◽  
Kim A. Nasmyth ◽  
Stephan Uphoff
Keyword(s):  
Single Molecule ◽  
Sister Chromatid ◽  
Fluorescence Recovery After Photobleaching ◽  
Sister Chromatid Cohesion ◽  
Dna Looping ◽  
Cohesin Complex ◽  
Single Molecule Tracking ◽  
Loading Function ◽  
Stop And Go ◽  
Chromatid Cohesion

AbstractThe cohesin complex mediates DNA-DNA interactions both between (sister chromatid cohesion) and within chromosomes (DNA looping) via a process thought to involve entrapment of DNAs within its tripartite ring. It has been suggested that intra- chromosome loops are generated through processive extrusion of DNAs through the lumen of cohesin’s ring. Scc2 (Nipbl) is essential for loading cohesin onto chromosomes but not for maintaining sister chromatid cohesion following DNA replication. It has therefore been assumed that Scc2 is involved exclusively in the cohesin loading process. However, it is possible that the stimulation of cohesin’s ABC-like ATPase by Scc2 also has a post-loading function, for example driving loop extrusion. Using fluorescence recovery after photobleaching (FRAP) and single-molecule tracking, we show that Scc2 binds dynamically to chromatin, principally through an association with cohesin. Scc2’s movement within chromatin is consistent with a “stop-and-go” or “hopping” motion. We suggest that a low diffusion coefficient, a low stoichiometry relative to cohesin, and a high affinity for chromosomal cohesin enables Scc2 to move rapidly from one chromosomal cohesin complex to another, performing a function distinct from loading.

scholarly journals A conserved activity for cohesin in bridging DNA molecules

2019 ◽  
Author(s):  
Pilar Gutierrez-Escribano ◽  
Matthew D. Newton ◽  
Aida Llauró ◽  
Jonas Huber ◽  
Loredana Tanasie ◽  
...  
Keyword(s):  
Single Molecule ◽  
Sister Chromatid ◽  
Regulation Of Gene Expression ◽  
Sister Chromatid Cohesion ◽  
Dna Molecules ◽  
Chromosome Architecture ◽  
Physiological Conditions ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Core Activity

AbstractEssential processes such as accurate chromosome segregation, regulation of gene expression and DNA repair rely on protein-mediated DNA tethering. Sister chromatid cohesion requires the SMC complex cohesin to act as a protein linker that holds replicated chromatids together (1, 2). The molecular mechanism by which cohesins hold sister chromatids has remained controversial. Here, we used a single molecule approach to visualise the activity of cohesin complexes as they hold DNA molecules. We describe a DNA bridging activity that requires ATP and is conserved from yeast to human cohesin. We show that cohesin can form two distinct classes of bridges at physiological conditions, a “permanent bridge” able to resists high force (over 80pN) and a “reversible bridge” that breaks at lower forces (5-40pN). Both classes of bridges require Scc2/Scc4 in addition to ATP. We demonstrate that bridge formation requires physical proximity of the DNA segments to be tethered and show that “permanent” cohesin bridges can move between two DNA molecules but cannot be removed from DNA when they occur in cis. This suggests that separate physical compartments in cohesin molecules are involved in the bridge. Finally, we show that cohesin tetramers, unlike condensin, cannot compact linear DNA molecules against low force, demonstrating that the core activity of cohesin tetramers is bridging DNA rather than compacting it. Our findings carry important implications for the understanding of the basic mechanisms behind cohesin-dependent establishment of sister chromatid cohesion and chromosome architecture.

scholarly journals Establishment of Sister Chromatid Cohesion at the S. cerevisiae Replication Fork

2006 ◽  
Vol 23 (6) ◽  
pp. 787-799 ◽  
Author(s):  
Armelle Lengronne ◽  
John McIntyre ◽  
Yuki Katou ◽  
Yutaka Kanoh ◽  
Karl-Peter Hopfner ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Replication Fork ◽  
Sister Chromatid Cohesion ◽  
Chromatid Cohesion

scholarly journals Functional Coupling between DNA Replication and Sister Chromatid Cohesion Establishment

2021 ◽  
Vol 22 (6) ◽  
pp. 2810
Author(s):  
Ana Boavida ◽  
Diana Santos ◽  
Mohammad Mahtab ◽  
Francesca M. Pisani
Keyword(s):  
Dna Replication ◽  
Sister Chromatid ◽  
Molecular Mechanisms ◽  
Sister Chromatid Cohesion ◽  
Functional Coupling ◽  
Functional Link ◽  
Chromatid Cohesion ◽  
Evolutionarily Conserved ◽  
Eukaryotic Organisms ◽  
Replication Factors

Several lines of evidence suggest the existence in the eukaryotic cells of a tight, yet largely unexplored, connection between DNA replication and sister chromatid cohesion. Tethering of newly duplicated chromatids is mediated by cohesin, an evolutionarily conserved hetero-tetrameric protein complex that has a ring-like structure and is believed to encircle DNA. Cohesin is loaded onto chromatin in telophase/G1 and converted into a cohesive state during the subsequent S phase, a process known as cohesion establishment. Many studies have revealed that down-regulation of a number of DNA replication factors gives rise to chromosomal cohesion defects, suggesting that they play critical roles in cohesion establishment. Conversely, loss of cohesin subunits (and/or regulators) has been found to alter DNA replication fork dynamics. A critical step of the cohesion establishment process consists in cohesin acetylation, a modification accomplished by dedicated acetyltransferases that operate at the replication forks. Defects in cohesion establishment give rise to chromosome mis-segregation and aneuploidy, phenotypes frequently observed in pre-cancerous and cancerous cells. Herein, we will review our present knowledge of the molecular mechanisms underlying the functional link between DNA replication and cohesion establishment, a phenomenon that is unique to the eukaryotic organisms.

scholarly journals Saccharomyces cerevisiae CTF18 and CTF4 Are Required for Sister Chromatid Cohesion

2001 ◽  
Vol 21 (9) ◽  
pp. 3144-3158 ◽  
Author(s):  
Joseph S. Hanna ◽  
Evgueny S. Kroll ◽  
Victoria Lundblad ◽  
Forrest A. Spencer
Keyword(s):  
Sister Chromatid ◽  
Replication Fork ◽  
Spindle Assembly Checkpoint ◽  
Budding Yeast ◽  
Sister Chromatid Cohesion ◽  
Nuclear Antigen ◽  
Chromatid Cohesion ◽  
Core Components ◽  
Proliferating Cell

ABSTRACT CTF4 and CTF18 are required for high-fidelity chromosome segregation. Both exhibit genetic and physical ties to replication fork constituents. We find that absence of eitherCTF4 or CTF18 causes sister chromatid cohesion failure and leads to a preanaphase accumulation of cells that depends on the spindle assembly checkpoint. The physical and genetic interactions between CTF4, CTF18, and core components of replication fork complexes observed in this study and others suggest that both gene products act in association with the replication fork to facilitate sister chromatid cohesion. We find that Ctf18p, anRFC1-like protein, directly interacts with Rfc2p, Rfc3p, Rfc4p, and Rfc5p. However, Ctf18p is not a component of biochemically purified proliferating cell nuclear antigen loading RF-C, suggesting the presence of a discrete complex containing Ctf18p, Rfc2p, Rfc3p, Rfc4p, and Rfc5p. Recent identification and characterization of the budding yeast polymerase κ, encoded by TRF4, strongly supports a hypothesis that the DNA replication machinery is required for proper sister chromatid cohesion. Analogous to the polymerase switching role of the bacterial and human RF-C complexes, we propose that budding yeast RF-CCTF18 may be involved in a polymerase switch event that facilities sister chromatid cohesion. The requirement for CTF4 and CTF18 in robust cohesion identifies novel roles for replication accessory proteins in this process.

scholarly journals MCM2–7-dependent cohesin loading during S phase promotes sister-chromatid cohesion

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Ge Zheng ◽  
Mohammed Kanchwala ◽  
Chao Xing ◽  
Hongtao Yu
Keyword(s):  
Sister Chromatid ◽  
Replication Fork ◽  
Sister Chromatid Cohesion ◽  
S Phase ◽  
Nucleosome Assembly ◽  
Okazaki Fragment ◽  
Replicative Helicase ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Okazaki Fragment Processing

DNA replication transforms cohesin rings dynamically associated with chromatin into the cohesive form to establish sister-chromatid cohesion. Here, we show that, in human cells, cohesin loading onto chromosomes during early S phase requires the replicative helicase MCM2–7 and the kinase DDK. Cohesin and its loader SCC2/4 (NIPBL/MAU2 in humans) associate with DDK and phosphorylated MCM2–7. This binding does not require MCM2–7 activation by CDC45 and GINS, but its persistence on activated MCM2–7 requires fork-stabilizing replisome components. Inactivation of these replisome components impairs cohesin loading and causes interphase cohesion defects. Interfering with Okazaki fragment processing or nucleosome assembly does not impact cohesion. Therefore, MCM2–7-coupled cohesin loading promotes cohesion establishment, which occurs without Okazaki fragment maturation. We propose that the cohesin–loader complex bound to MCM2–7 is mobilized upon helicase activation, transiently held by the replisome, and deposited behind the replication fork to encircle sister chromatids and establish cohesion.

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