Polymer Models of S. pombe Chromatin

Recent advances in Hi-C studies have laid the groundwork for understanding the organization of the genome at different points in the cell cycle. We present a coarse-grained polymer model with short-ranged attractions and volume exclusion that quantitatively recapitulates experimental Hi-C maps for the yeast strain, S. pombe. The polymer model gives rise to an ensemble of transient clusters corresponding to topologically associated domains. Insight on the dynamics of chromatin can be obtained from single particle tracking experiments on fluorescently tagged transgenic loci at strategic points in the genome. Transcription inhibitors have been shown to dramatically suppress the mean square displacements of the loci. These results imply that transcription is the source of activity within the nuclear envelope. We have also developed a coarse-grained model of polymerase translocating along a polymer. We model portions of the genome to identify the effect of activity on loci proximal and distal to regions of high gene expression.