Arabidopsis MSI1 connects LHP1 to PRC2 complexes

Abstract

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.

Identification of LEC1, L1L and Polycomb Repressive Complex 2 genes and their expression during the induction phase of Medicago truncatula Gaertn. somatic embryogenesis

“…The higher expression in the non-embryogenic line may play an inhibitory role in this process, so -because of the difference in the expression of these genes-primary explants may possess a different level of chromatin trimethylation and a changed ability to step in SE. Involvement of FIE and MSI1 genes in determining the H3K27me3 level has been confirmed in A. thaliana (Bouyer et al 2011;Derkacheva et al 2013).…”

The second subunit of DNA-polymerase delta is required for genomic stability and epigenetic regulation

“…Meanwhile, some studies indicate that the catalytic subunit of DNA polymerase a interacts with (Barrero et al, 2007) or perturbs the binding of like-heterochromatin protein 1 (LHP1; Hyun et al, 2013), which is the main reader/effector for H3K27me3 in Arabidopsis (Barrero et al, 2007;Zhang et al, 2007). Another link between DNA replication and H3K27me3 is MSI1 (multicopy suppressor of ira1), a chromatin assembly factor in Arabidopsis, which interacts with PcG protein and LHP1 (Derkacheva et al, 2013). So, it is possible that a dysfunctional Pol d may disturb the entire replication machinery, which would interfere with the recruitment of LHP1 or PcG proteins to PcG targets.…”

Deciphering the Role of POLYCOMB REPRESSIVE COMPLEX1 Variants in Regulating the Acquisition of Flowering Competence in Arabidopsis

“…These different PRC1 activities suggest the existence of PRC1 functional variants that may target different subsets of genes (Merini and Calonje, 2015). Another protein used to be considered as a putative PRC1 component is LIKE-HETEROCHROMATIN PROTEIN1 (LHP1), which has the ability to bind H3K27me3 marks (Turck et al, 2007); however, it was recently shown that LHP1 copurifies with PRC2, changing the notion of LHP1 as a PRC1 component (Derkacheva et al, 2013).From a mechanistic point of view, recent data indicated that the binding and activity of PRC1 are required for H3K27me3 marking at some target genes, …”