DNA tethering mechanisms of cohesins and auxiliary factors. Schematic representation of the cohesin ring structure (composed of the five subunits: SMC1A, SMC3, RAD21, SA1,2, and PDS5) and auxiliary factors NIPBL (loader), ESCO2 (acetyltransferase), and HDAC8 (deacetylase). Cohesins and auxiliary factors regulate both cis- and trans-DNA tethering events. Cis-DNA tethering processes include DNA looping mechanisms during transcription, condensation, and ribosome biogenesis. Trans-DNA tethering processes include sister chromatid segregation during S phase of cell cycle and DNA repair events.

Mechanisms of cohesinopathies. Transcriptional deregulation caused by defects in cis-DNA tethering events is the predominant mechanism through which both RBS and CdLS arise. The extent to which mitotic failure and apoptosis caused by defects in trans-DNA tethering events contribute to cohesinopathies requires further inquiry.