AtEAF1 is a potential platform protein for Arabidopsis NuA4 acetyltransferase complex.

BACKGROUND: Histone acetyltransferase complex NuA4 and histone variant exchanging complex SWR1 are two chromatin modifying complexes which act cooperatively in yeast and share some intriguing structural similarities. Protein subunits of NuA4 and SWR1-C are highly conserved across eukaryotes, but form different multiprotein arrangements. For example, the human TIP60-p400 complex consists of homologues of both yeast NuA4 and SWR1-C subunits, combining subunits necessary for histone acetylation and histone variant exchange. It is currently not known what protein complexes are formed by the plant homologues of NuA4 and SWR1-C subunits. RESULTS: We report on the identification and molecular characterization of AtEAF1, a new subunit of Arabidopsis NuA4 complex which shows many similarities to the platform protein of the yeast NuA4 complex. AtEAF1 copurifies with Arabidopsis homologues of NuA4 and SWR1-C subunits ARP4 and SWC4 and interacts physically with AtYAF9A and AtYAF9B, homologues of the YAF9 subunit. Plants carrying a T-DNA insertion in one of the genes encoding AtEAF1 showed decreased FLC expression and early flowering, similarly to Atyaf9 mutants. Chromatin immunoprecipitation analyses of the single mutant Ateaf1b-2 and artificial miRNA knock-down Ateaf1 lines showed decreased levels of H4K5 acetylation in the promoter regions of major flowering regulator genes, further supporting the role of AtEAF1 as a subunit of the plant NuA4 complex. CONCLUSIONS: Growing evidence suggests that the molecular functions of the NuA4 and SWR1 complexes are conserved in plants and contribute significantly to plant development and physiology. Our work provides evidence for the existence of a yeast-like EAF1 platform protein in A. thaliana, filling an important gap in the knowledge about the subunit organization of the plant NuA4 complex

Natural variation identifies SNI1, the SMC5/6 component, as a modifier of meiotic crossover in Arabidopsis.

The frequency and distribution of meiotic crossovers are tightly controlled; however, variation in this process can be observed both within and between species. Using crosses of two natural Arabidopsis thaliana accessions, Col and Ler, we mapped a crossover modifier locus to semidominant polymorphisms in SUPPRESSOR OF NPR1-1 INDUCIBLE 1 (SNI1), which encodes a component of the SMC5/6 complex. The sni1 mutant exhibits a modified pattern of recombination across the genome with crossovers elevated in chromosome distal regions but reduced in pericentromeres. Mutations in SNI1 result in reduced crossover interference and can partially restore the fertility of a Class I crossover pathway mutant, which suggests that the protein affects noninterfering crossover repair. Therefore, we tested genetic interactions between SNI1 and both RECQ4 and FANCM DNA helicases, which showed that additional Class II crossovers observed in the sni1 mutant are FANCM independent. Furthermore, genetic analysis of other SMC5/6 mutants confirms the observations of crossover redistribution made for SNI1 The study reveals the importance of the SMC5/6 complex in ensuring the proper progress of meiotic recombination in plants

NuA4 and H2A.Z control environmental responses and autotrophic growth in Arabidopsis.

Nucleosomal acetyltransferase of H4 (NuA4) is an essential transcriptional coactivator in eukaryotes, but remains poorly characterized in plants. Here, we describe Arabidopsis homologs of the NuA4 scaffold proteins Enhancer of Polycomb-Like 1 (AtEPL1) and Esa1-Associated Factor 1 (AtEAF1). Loss of AtEAF1 results in inhibition of growth and chloroplast development. These effects are stronger in the Atepl1 mutant and are further enhanced by loss of Golden2-Like (GLK) transcription factors, suggesting that NuA4 activates nuclear plastid genes alongside GLK. We demonstrate that AtEPL1 is necessary for nucleosomal acetylation of histones H4 and H2A.Z by NuA4 in vitro. These chromatin marks are diminished genome-wide in Atepl1, while another active chromatin mark, H3K9 acetylation (H3K9ac), is locally enhanced. Expression of many chloroplast-related genes depends on NuA4, as they are downregulated with loss of H4ac and H2A.Zac. Finally, we demonstrate that NuA4 promotes H2A.Z deposition and by doing so prevents spurious activation of stress response genes

Structure and function of the plant histone acetyltransferase NuA4

Wydział Biologii: Instytut Biologii Molekularnej i BiotechnologiiJednym z głównych mechanizmów wykorzystywanych przez rośliny do regulacji transkrypcji są modyfikacje chromatyny. Drożdżowy kompleks nukleosomalnej acetylotransferazy histonu H4 (NuA4) jest jednym z najintensywniej badanych enzymów modyfikujących chromatynę. Homologi prawie wszystkich podjednostek NuA4 występują także u roślin, jednak dane eksperymentalne na temat roślinnego kompleksu NuA4 są wciąż ubogie. Przedstawiona tu analiza roślinnego kompleksu NuA4 polegała na próbie potwierdzenia fizycznych i funkcjonalnych oddziaływań pomiędzy jego podjednostkami. Strategia eksperymentalna opierała się na połączeniu metod genetycznych (analiza mutantów insercyjnych, edytowanie genomu za pomocą CRISPR/Cas9), biochemicznych (koimmunoprecypitacja) i mikroskopowych (BiFC). Uzyskane wyniki pozwoliły na identyfikację nieznanej wcześniej podjednostki kompleksu oraz na ujawnienie związku funkcjonalnego pomiędzy NuA4 i rozwojem chloroplastów. Przedstawiona praca może się przyczynić do lepszego zrozumienia budowy i funkcji roślinnego kompleksu NuA4 poprzez rozszerzenie repertuaru znanych podjednostek oraz funkcji tego enzymu. Możliwy udział roślinnego kompleksu NuA4 w regulacji działania aparatu fotosyntetycznego na poziomie transkrypcji jest nieoczekiwanym odkryciem, jednak dobrze przystaje do obecnej wiedzy na temat udziału acetylacji histonów w tym procesie.Plants use chromatin modifications extensively to control transcription in development, reproduction and response to environmental challenges. The yeast Nucleosomal Acetyltransferase of histone H4 (NuA4) complex is one of the most intensively studied chromatin-modifying enzymes. Homologues of almost all NuA4 subunits are present in plants, however, experimental data on the plant NuA4 complex is scarce. The analysis of the plant NuA4 complex, presented herein, focuses on the physical and functional interactions between its subunits. Experimental strategy involved a combination of genetic (analysis of insertional mutants, genome editing by CRISPR/Cas9), biochemical (co-immunoprecipitation) and microscopy-based methods (BiFC). The obtained results allowed for the identification of a previously unknown subunit of the complex and revealed a link between plant NuA4 and chloroplast development. The work presented herein adds to the present understanding of the plant NuA4 structure and function by expanding the repertoires of known subunits and functions of the complex. The possible involvement of plant NuA4 in the transcriptional regulation of the photosynthetic apparatus is an unexpected discovery which, nevertheless, matches well with what is currently known about the role of histone acetylation in this process