Abstract
BackgroundHistone 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.ResultsWe 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.ConclusionsGrowing 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0461-1) contains supplementary material, which is available to authorized users.
Highlights
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
An uncharacterized plant-specific domain-relative of the yeast EAF1 protein is physically associated with AtARP4 and AtSWC4 We used affinity purification followed by tandem mass spectrometry (AP-MS/MS) to test which Arabidopsis homologues of yeast NuA4 and SWR1-C are associated with the common protein module of the two complexes
In agreement with a recently published study [20], we found multiple subunits of the SWI/SNF complex among proteins copurified with AtARP4, suggesting that besides NuA4, SWR1-C and INO80, AtARP4 interacts with SWI/SNF in plants
Summary
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. 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. Eukaryotic chromatin has evolved for seemingly contradictory functions It ensures compaction and protection of genetic material, and controls diverse processes including transcription, replication and DNA repair that require a relatively open and dynamic chromatin structure. This mixture of robustness and flexibility is achieved by a number of specialized enzymes that remodel chromatin or modify nucleosomes by covalent histone modifications. Acetylation of nucleosomal histones has a strong influence on the action of chromatin remodeling complexes such as RSC [1], SWI/SNF [2], INO80 [3] or SWR1-C [4]
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