Fig. 6. Working model for the formation of Hfq-polyP–based heterochromatin in E. coli.

In WT E. coli (lower left quadrant), Hfq, polyP, and DNA work together to form bacterial heterochromatin by creating phase-separated droplets. PolyP drives the formation of these structures preferentially over AT-rich regions including prophages and MGEs, whose mobilization could damage the cell. The absence of polyP (top right quadrant) leads to the reorganization of the bacterial chromatin with an overall decrease in Hfq-heterochromatin complexes, and the relocation of Hfq from AT-rich to more GC-enrich motifs. This leads to the unsolicited derepression of toxic MGE sequences.