Linking Chromosome Duplication and Segregation via Sister Chromatid Cohesion

Abstract

DNA replication during S phase generates two identical copies of each chromosome. Each chromosome is destined for a daughter cell, but each daughter must receive one and only one copy of each chromosome. To ensure accurate chromosome segregation, eukaryotic cells are equipped with a mechanism to pair the chromosomes during chromosome duplication and hold the pairs until a bi-oriented mitotic spindle is formed and the pairs are pulled apart. This mechanism is known as sister chromatid cohesion, and its actions span the entire cell cycle. During G1, before DNA is copied during S phase, proteins termed cohesins are loaded onto DNA. Paired chromosomes are held together through G2 phase, and finally the cohesins are dismantled during mitosis. The processes governing sister chromatid cohesion ensure that newly replicated sisters are held together from the moment they are generated to the metaphase–anaphase transition, when sisters separate.

Functional Coupling between DNA Replication and Sister Chromatid Cohesion Establishment

“…A natural context for this conversion is present at the replication forks, where the newly duplicated sister chromatids are transiently bridged by the DNA replication machinery. The existence of a functional coupling between chromosomal cohesion and replication is exemplified by the finding that, on one hand, down-regulating several cohesin regulators has consequences on replication fork dynamics [ 34 , 35 , 36 ] and, on the other hand, loss of many components of the replication machinery gives rise to sister chromatid cohesion defects [ 37 , 38 ]. A list of these replication proteins, named “cohesion establishment factors”, is reported in Table 1 .…”

Reduced activity ofArabidopsischromosome-cohesion regulator geneCTF7/ECO1alters cytosine methylation status and retrotransposon expression

“…1 During metaphase, chromosome copies, known as sister chromatids, become associated with the spindle and align along the mid-plane of the cell, then one sister from each pair becomes associated with a different spindle pole. 2 A cohesin complex is responsible for physically tethering sister chromatids and homologous chromosomes during the cell cycle. 1 The physical tethering must be removed for sisters to move toward each pole.…”

“…1 The physical tethering must be removed for sisters to move toward each pole. 2 This multisubunit cohesin protein complex, formed by proteins of the STRUCTURAL MAINTENANCE OF CHRO-MOSOMES (SMC) family and associated non-SMC factors, is essential for regulating the higher-order chromosomal structure in eukaryotes. 3 Canonical SMC proteins are about 1000 amino acids long and are loaded onto chromosomes during telophase and G 1 phase before DNA replication.…”

Comparative genomics of HORMA domain-containing proteins in prokaryotes and eukaryotes

“…Advances in comparative genomics and bioinformatic tools may potentially improve our understanding of the evolution of organisms. It is commonly known that many proteins which are involved in cell division are conserved among prokaryotes and eukaryotes, such as ATPase family proteins [32], several key enzymes of the apoptotic machinery [33] and structural maintenance of chromosomes complex [34]. However, no experimental reports describe the role of HORMAcontaining proteins in cell division in prokaryotes.…”