Chromosomes as communication and memory devices

Chromosomes are long polymers of DNA decorated by myriads of proteins. We are interested in understanding how cells fold them to read, write, and process genetic and epigenetic information. Can the ways chromosomes are folded carry information itself?

 Recent work from my group and others has shown that chromosomes are active polymers. First, we found that chromosomes are folded by the active (ATP-dependent) process of “loop extrusion”, where molecular motors form progressively larger loops. The collective action of these nanometer-sized motors shapes micron-sized chromosomes. This active mechanism also enables long-range communication between the “regulatory genome” and protein-coding genes.

 Second, we found that chromosome folding can help store “epigenetic memory,” patterns of chemical marks along the genome. Such marks are lost and spread by enzymes, yet when marks influence genome folding, the pattern of marks can be preserved for hundreds of cell divisions. We further identified a parallel between this mechanism of epigenetic memory and associative memory in a neural network, suggesting that this system may perform more complex information processing tasks.