7o6u
From Proteopedia
Crystal structure of the VIN3 VEL polymerising domain (R554A R556D mutant)
Structural highlights
FunctionVIN3_ARATH Plays a central role in vernalization by mediating the initial transcriptional repression of the homeotic gene FLC, a floral repressor, after a cold treatment. However, due to its transient expression, it cannot maintain repression of FLC, which is then maintained by Polycomb Group complexes containing VRN2 throughout development. Required to deacetylate histones on the FLC promoter. Together with VIL1, required during vernalization for the modifications of FLC and FLM chromatin that are associated with an epigenetically silenced state (e.g. chromatin modifications, histone deacetylation, and trimethylated H3 'Lys-4' H3K4me3 and 'Lys-27' H3K27me3) and with acquisition of competence to flower.[1] [2] [3] Publication Abstract from PubMedTranscriptional silencing through the Polycomb silencing machinery utilizes a "read-write" mechanism involving histone tail modifications. However, nucleation of silencing and long-term stable transmission of the silenced state also requires P-olycomb Repressive Complex 2 (PRC2) accessory proteins, whose molecular role is poorly understood. The Arabidopsis VEL proteins are accessory proteins that interact with PRC2 to nucleate and propagate silencing at the FLOWERING LOCUS C (FLC) locus, enabling early flowering in spring. Here, we report that VEL proteins contain a domain related to an atypical four-helix bundle that engages in spontaneous concentration-dependent head-to-tail polymerization to assemble dynamic biomolecular condensates. Mutations blocking polymerization of this VEL domain prevent Polycomb silencing at FLC. Plant VEL proteins thus facilitate assembly of dynamic multivalent Polycomb complexes required for inheritance of the silenced state. Head-to-tail polymerization by VEL proteins underpins cold-induced Polycomb silencing in flowering control.,Fiedler M, Franco-Echevarria E, Schulten A, Nielsen M, Rutherford TJ, Yeates A, Ahsan B, Dean C, Bienz M Cell Rep. 2022 Nov 8;41(6):111607. doi: 10.1016/j.celrep.2022.111607. PMID:36351412[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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