Core histone-binding subunit that may target chromatin assembly factors, chromatin remodeling factors and histone deacetylases to their histone substrates in a manner that is regulated by nucleosomal DNA. Component of the flowering autonomous pathway which positively regulates flowering by promoting transcriptional repression of the flowering repressor FLC. May promote histone deacetylation at the FLC locus leading to the formation of repressive chromatin structures. Forms a histone deacetylase complex with HDA5, HDA6 and FLD that represses FLC gene expression to control flowering time (PubMed:25922987). Also negatively regulates cold-responsive genes. Acts together with PDP1 and MSI5 to regulate the function of the PRC2 complex on FLC (PubMed:29314758). Required for systemic acquired resistance (SAR) toward pathogenic bacteria (e.g. Pseudomonas syringae pv tomato DC3000 (avrPto)) (PubMed:32392578). Together with FLD and MSI4/FVE, contributes to dehydroabietinal-dependent (DA, a diterpenoid tricyclic diterpene) activation of flowering ans SAR (PubMed:32392578). Interacts with AHL16 and HOS1 (PubMed:22960247, PubMed:23394836). Interacts with LHP1, PDP1, PDP2 and PDP3 (PubMed:29314758). Component of the PRC2 (polycomb repressive complex 2) complex which regulates histone methylation on histone H3K27 (PubMed:29314758). Expressed in rosette leaves, cauline leaves, main stems and developing fruits. Expressed at higher levels in roots and flowers. Induced by dehydroabietinal-dependent (DA), a diterpenoid tricyclic diterpene that promotes flowering and systemic acquired resistance (SAR). The DWD box is required for interaction with DDB1A. Reduced H3K27me3 level but increased levels of histone H3 acetylation and H3K4me3 on FLC in the fve msi5 double mutant (PubMed:29314758). Delayed flowering (PubMed:32392578). Impaired systemic acquired resistance (SAR) toward pathogenic bacteria (e.g. Pseudomonas syringae pv tomato DC3000 (avrPto)) (PubMed:32392578). Lost ability of dehydroabietinal-dependent (DA, a diterpenoid tricyclic diterpene) to trigger flowering and systemic acquired resistance (SAR) (PubMed:32392578). Binds zinc. Belongs to the WD repeat RBAP46/RBAP48/MSI1 family. Truncated N-terminus.