Chromosomes as communication and memory machines

by Leonid A. Mirny (Institute for Medical Engineering and Science, and Department of Physics Massachusetts Institute of Technology, Cambridge, MA)

Tuesday 23 Sept 2025, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dipartimento di Fisica-Ed. G.Marconi)

Chromosomes are long polymers of genomic DNA decorated with proteins.
We are interested in understanding how cells fold chromosomes to read,
write, and process genetic and epigenetic information. Could the way
chromosomes are folded carry information itself?
First, we discovered that chromosomes are folded by the ATP-dependent
process of loop extrusion, where molecular motors form progressively
larger loops. This collective action of nanometer-sized motors shapes
micrometer-sized chromosomes. We demonstrated how this mechanism can
also establish complex long-range and targeted communication between
regulatory elements and genes.
Second, we found that chromosome folding plays a key role in storing
"epigenetic memory," which refers to patterns of chemical marks along
the genome. Although these marks are subject to loss and spreading by
enzymes, when genome folding is influenced by the marks, the pattern
can be preserved for hundreds of cell divisions. We also identified a
parallel between this mechanism of epigenetic memory and associative
memory in neural networks, suggesting that this system may be capable
of performing more complex information-processing tasks.