DECREASE IN DNA METHYLATION 1 (DDM1) Interacts with CHROMOMETHYLASE (CMT) and LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) in Physcomitrella patens.

The nucleosome remodeling protein decrease in DNA methylation 1 (DDM1)/Lsh maintains normal levels of DNA methylation. Direct interaction between Lsh and DNA methyltransferase 1 (Dnmt1) and their localization to heterochromatin in the presence of heterochromatin protein-1 alpha (HP1 alpha) is a mechanism by which the concentration of DNMTs is increased at heterochromatin, and chromosome structures are stabilized in metazoans. In plants, however, it is unclear how DDM1 cooperates with methyltransferases and like heterochromatin protein 1 (LHP1). In this study, we provide evidence for a novel interaction between moss DDM1 (PpDDM1) and the chromomethylase PpCMT, that has not been reported in any plant, and between PpDDM1 and PpLHP1, that has not been reported before in any organism. Our protein-protein interaction studies may provide mechanistic insight into heterochromatin regulation.