How are chromosomes held together by cohesin?

Each chromosome must be replicated to produce sister DNAs, which segregate to opposite sides of the cell during mitosis. Chromosomes metamorphose into threads largely segregated from their sisters but attached along an inter-chromatid axis through sister chromatid cohesion. This ensures that sister DNAs are pulled in opposite directions. Professor Nasmyth has identified proteins that mediate sister chromatid cohesion and shown that they form a multi-subunit ring-shaped complex called cohesin. He has proposed that cohesin holds sister DNAs together by trapping them within its ring structure. Professor Nasmyth aims to establish the universality of this 'ring model' to elucidate how DNAs enter and exit cohesin. He will also apply insights derived from cohesin to understanding how a related complex called condensin holds the DNA within individual chromatids together. This work will enrich chromosome biology and yield insights into tumours and age-related infertility in females.