Biophys. J. 103, 2223–2232 (2012)

There is an elegance inherent in the linear-polymer encoding of our genetic information. But what happens when distant locations along a single DNA strand need to occupy a single region in space? It turns out that many important cellular processes require such co-localization, but there is as yet no single plausible physical mechanism for it.

Now, Valentino Bianco and colleagues have shown that the interaction of specific DNA loci with diffusing molecular species can effectively induce co-localization, via a crossover characterized by the formation of a single unstable loci pair — the appearance of which should be observable in experiment.

Bianco et al. designed a pair of schematic models, implicating a general molecular mechanism for the self-organization of DNA in three dimensions. The two models differ in terms of the constraint they place on the valency of molecular species, which determines their ability to bridge two or more regions along the polymer.

When multiple bonds were allowed, Bianco et al. found that DNA loci came together in a single group, whereas the single-valency model engendered a more complex picture, involving independent sub-groups of loci. A comparison of their results with experimental data revealed scenarios corresponding to both models.