title: Reversion of the Arabidopsis UV-B photoreceptor UVR8 to the homodimeric ground state.
abstract: Plants require the UV-B photoreceptor UV resistance locus 8 (UVR8) for acclimation and survival in sunlight. Upon UV-B perception, UVR8 switches instantaneously from a homodimeric to monomeric configuration, which leads to interaction with the key signaling protein constitutively photomorphogenic 1 (COP1) and induction of UV-B-protective responses. Here, we show that UVR8 monomerization is reversible in vivo, restoring the homodimeric ground state. We also demonstrate that the UVR8-interacting proteins repressor of UV-B photomorphogenesis (RUP)1 and RUP2 mediate UVR8 redimerization independently of COP1. UVR8 redimerization consequently disrupts the UVR8-COP1 interaction, which halts signaling. Our results identify a key role of RUP1- and RUP2-mediated UVR8 redimerization in photoreceptor inactivation, a crucial process that regenerates reactivatable UVR8 homodimers.
authors.affiliation: Department of Botany and Plant Biology, Sciences III,  University of Geneva, CH-1211 Geneva 4,  Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Heijde
authors.forename: Roman
authors.initials: R
authors.lastname: Ulm
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017343:Genes, Plant; D009154:Mutation; D055519:Photoreceptors, Plant / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization / Q000528:radiation effects; D020836:Protein Structure, Quaternary / Q000528:radiation effects; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; D055519:Photoreceptors, Plant; D012097:Repressor Proteins; C525052:Uvr8 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases