Cohesion peculiarities in Eu- and heterochromatin in human cells

Sister chromatids are considered to be held together from just after replication until the beginning of compaction in prophase via a specific complex—cohesin consisting of Smc1-Smc3 dimer and two additional subunits Scc1 and Scc3, the process being referred to as “cohesion.” We have characterized peculiarities of binding of the cohesin complex with early and late replicating chromatin at various stages of the cell cycle in human cell lines HeLa and HT1080 using structured illumination microscopy and immune electron microscopy. It has been shown that cohesion in heterochromatic domains is evidently provided without the participation of cohesins, while the majority of cohesins bound to chromatin provides cohesion and subdomain organization in euchromatin.