Figure 3.

Three models for how Smc complexes may tether two DNA molecules/chromatin. Each model shows two strands of DNA/chromatin. These strands may come from two distinct DNA molecules (as expected for recombination or sister chromatid cohesion), or from a single DNA/chromatin molecule that is folded back on itself (as expected for regulation of gene expression or condensation). In the first model, the Smc complex embraces the two DNA strands. The snap model proposes that each Smc complex can bind a single strand and that tethering results from the oligomerization of the Smc complexes. The bracelet model suggests that Smc complexes can oligomerize to form filaments. Such filaments could be used in a number of ways to mediate tethering. One possible mechanism is shown here.