Chromatin architectural proteins regulate flowering time by precluding gene looping.

Abstract

Chromatin structure is critical for gene expression and many other cellular processes. In <i>Arabidopsis thaliana</i>, the floral repressor <i>FLC</i> adopts a self-loop chromatin structure via bridging of its flanking regions. This local gene loop is necessary for active <i>FLC</i> expression. However, the molecular mechanism underlying the formation of this class of gene loops is unknown. Here, we report the characterization of a group of linker histone-like proteins, named the GH1-HMGA family in <i>Arabidopsis</i>, which act as chromatin architecture modulators. We demonstrate that these family members redundantly promote the floral transition through the repression of <i>FLC</i> A genome-wide study revealed that this family preferentially binds to the 5' and 3' ends of gene bodies. The loss of this binding increases <i>FLC</i> expression by stabilizing the <i>FLC</i> 5' to 3' gene looping. Our study provides mechanistic insights into how a family of evolutionarily conserved proteins regulates the formation of local gene loops.