Fig. 8: Model of DDM1 activity for the maintenance of repressive marks.
From: Molecular and structural basis of the chromatin remodeling activity by Arabidopsis DDM1
The pericentromeric heterochromatin is occupied with H2A.W, which forms a condensed structure caused by the extended C-terminal tail of H2A.W interacting with the linker DNA, and the H3 αN and α2 helices. In the absence of H2A.W, the pericentromeric heterochromatin is occupied with H2A. The nucleosome containing H2A forms an open structure, caused by the loss of the interactions with the H3 αN and α2 helices. In the presence of DDM1, the C-terminal tail of H2A.W might dissociate from the linker DNA and H3 by interacting with DDM1. In addition, DDM1 slides nucleosomes containing H2A.W and H2A with identical efficiency. These activities might promote the increased accessibility of the heterochromatin to DNA methyltransferases.
