7d3y
Crystal structure of the osPHR2-osSPX2 complex
Structural highlights
FunctionH2AY_HUMAN Variant histone H2A which replaces conventional H2A in a subset of nucleosomes where it represses transcription. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. Involved in stable X chromosome inactivation. Inhibits the binding of transcription factors and interferes with the activity of remodeling SWI/SNF complexes. Inhibits histone acetylation by EP300 and recruits class I HDACs, which induces a hypoacetylated state of chromatin. In addition, isoform 1, but not isoform 2, binds ADP-ribose and O-acetyl-ADP-ribose, and may be involved in ADP-ribose-mediated chromatin modulation.[1] [2] [3] [4] [5] SPX2_ORYSI Inhibits PHR2 DNA-binding activity via a phosphate (Pi)-dependent protein interaction (By similarity). Together with SPX1, plays a negative role in the regulation of leaf inclination by preventing RLI1 transcription factor activity in Pi depleted conditions (By similarity).[UniProtKB:Q6Z784] Publication Abstract from PubMedPhosphate (Pi) starvation response (PHR) transcription factors play key roles in plant Pi homeostasis maintenance. They are negatively regulated by stand-alone SPX proteins, cellular receptors for inositol pyrophosphate (PP-InsP) nutrient messengers. How PP-InsP-bound SPX interacts with PHRs is poorly understood. Here, we report crystal structures of the rice SPX2/InsP(6)/PHR2 complex and of the PHR2 DNA binding (MYB) domain in complex with target DNA at resolutions of 3.1 A and 2.7 A, respectively. In the SPX2/InsP(6)/PHR2 complex, the signalling-active SPX2 assembles into a domain-swapped dimer conformation and binds two copies of PHR2, targeting both its coiled-coil (CC) oligomerisation domain and MYB domain. Our results reveal that the SPX2 senses PP-InsPs to inactivate PHR2 by establishing severe steric clashes with the PHR2 MYB domain, preventing DNA binding, and by disrupting oligomerisation of the PHR2 CC domain, attenuating promoter binding. Our findings rationalize how PP-InsPs activate SPX receptor proteins to target PHR family transcription factors. Mechanistic insights into the regulation of plant phosphate homeostasis by the rice SPX2 - PHR2 complex.,Guan Z, Zhang Q, Zhang Z, Zuo J, Chen J, Liu R, Savarin J, Broger L, Cheng P, Wang Q, Pei K, Zhang D, Zou T, Yan J, Yin P, Hothorn M, Liu Z Nat Commun. 2022 Mar 24;13(1):1581. doi: 10.1038/s41467-022-29275-8. PMID:35332155[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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