Highly heterogeneous long-range interactions explain chromosome compartmentalization

Abstract

The explanation for the compartmentalization of the chromosome contact maps observed by Hi-C method is still an unsolved mystery. The most natural and generally accepted explanation is that blocks of frequent/rare contacts on the entire map are associated with the existence of blocks of homogeneous elements along the chromosome that interact in 3D so that elements of the same type interact frequently and those of different types rarely. We study the polymer model of the chromosome, in which there are neither blocks of homogeneous elements nor homogeneous interactions and all the interaction energies are different. We demonstrate that such a heteropolymer model is able to describe chromosomal maps with high accuracy. The differences from compartment polymer models of chromosomes, which actually reflect the mechanism of microphase separation in polymers, are discussed further.