Arabidopsis MSI1 connects LHP1 to PRC2 complexes

EMBO J. 2013 Jul 17;32(14):2073-85. doi: 10.1038/emboj.2013.145. Epub 2013 Jun 18.


Polycomb group (PcG) proteins form essential epigenetic memory systems for controlling gene expression during development in plants and animals. However, the mechanism of plant PcG protein functions remains poorly understood. Here, we probed the composition and function of plant Polycomb repressive complex 2 (PRC2). This work established the fact that all known plant PRC2 complexes contain MSI1, a homologue of Drosophila p55. While p55 is not essential for the in vitro enzymatic activity of PRC2, plant MSI1 was required for the functions of the EMBRYONIC FLOWER and the VERNALIZATION PRC2 complexes including trimethylation of histone H3 Lys27 (H3K27) at the target chromatin, as well as gene repression and establishment of competence to flower. We found that MSI1 serves to link PRC2 to LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), a protein that binds H3K27me3 in vitro and in vivo and is required for a functional plant PcG system. The LHP1-MSI1 interaction forms a positive feedback loop to recruit PRC2 to chromatin that carries H3K27me3. Consequently, this can provide a mechanism for the faithful inheritance of local epigenetic information through replication.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Chromosomal Proteins, Non-Histone / chemistry
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosomal Proteins, Non-Histone / metabolism*
  • Epigenesis, Genetic
  • Gene Expression Regulation, Plant
  • Genes, Plant
  • MADS Domain Proteins / genetics
  • Models, Molecular
  • Multiprotein Complexes / chemistry
  • Multiprotein Complexes / metabolism
  • Plants, Genetically Modified
  • Polycomb Repressive Complex 2
  • Protein Interaction Domains and Motifs
  • Repressor Proteins / chemistry
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*


  • Arabidopsis Proteins
  • Chromosomal Proteins, Non-Histone
  • FLF protein, Arabidopsis
  • MADS Domain Proteins
  • MSI1 protein, Arabidopsis
  • Multiprotein Complexes
  • PRC2 protein, Arabidopsis
  • Repressor Proteins
  • like heterochromatin protein 1
  • Polycomb Repressive Complex 2