Role of Yng2 PHD and CHD-containing Eaf3 subunits of NuA4 on genome wide histone H4K8 acetylation, NuA4 localization and Pol II distribution
Ontology highlight
ABSTRACT: The NuA4 acetyltransferase complex contains two reader modules, an H3K4me3-specific PHD domain within the Yng2 subunit and H3K36me2/3-specific chromodomain in the Eaf3 subunit. The objectives of this study are to evaluate the role these two reader modules on NuA4 genome-wide localization, histone H4K8 acetylation and RNA polymerase II occupancy. We demonstrate here that Yng2 PHD specifically directs H4 acetylation near the transcription start site of highly expressed genes while Eaf3 is important downstream on the body of the genes. Strikingly, the recruitment of the NuA4 complex to these loci is not significantly affected. Furthermore, RNA polymerase II occupancy is decreased only in conditions where both PHD and chromo domains are lost, and mostly in the second half of the gene coding regions. Altogether, these results argue that methylated histone reader modules in NuA4 are not important for its recruitment on the promoter or coding regions but rather orient its acetyltransferase catalytic site to the methylated H3-bearing nucleosomes in the surrounding chromatin, allowing proper transcription initiation and elongation.
Project description:Nucleosomes must be deacetylated behind elongating RNA polymerase II to prevent cryptic initiation of transcription within the coding region. RNA polymerase II signals for deacetylation through methylation of histone H3 lysine 36 (H3K36) which provides the recruitment signal for the Rpd3S deacetylase complex. Recognition of methyl-H3K36 by Rpd3S requires the chromodomain of its Eaf3 subunit. Paradoxically, Eaf3 is also a subunit of the NuA4 acetyltransferase complex yet NuA4 does not recognize methyl H3K36 nucleosomes. We found that methyl H3K36 nucleosome recognition by Rpd3S also requires the PHD domain of its Rco1 subunit. Thus, the coupled chromo and PHD domains of Rpd3S specifies recognition of the methyl H3K36 mark; demonstrating the first combinatorial domain requirement within a protein complex to read a specific histone code.
Project description:The human NuA4/TIP60 co-activator complex, a fusion of the yeast SWR1 and NuA4 complexes, both incorporates the histone variant H2A.Z into nucleosomes and acetylates histones H4/H2A/H2A.Z to play crucial roles regulating gene expression and maintaining genome stability. Our cryo-EM studies show that within the NuA4/TIP60 complex, the EP400 subunit serves as an architectural scaffold holding the different functional modules in specific positions and giving rise to a novel arrangement of the ARP module. EP400 interacts with the TRRAP subunit using a footprint that overlaps with that of the SAGA acetyltransferase complex, thereby preventing the formation of a hybrid complex. Loss of the TRRAP subunit leads to mislocalization of NuA4/TIP60, resulting in the redistribution of H2A.Z and its acetylation across the genome, emphasizing the dual functionality of NuA4/TIP60 as a single macromolecular assembly.
Project description:The human NuA4/TIP60 co-activator complex, a fusion of the yeast SWR1 and NuA4 complexes, both incorporates the histone variant H2A.Z into nucleosomes and acetylates histones H4/H2A/H2A.Z to play crucial roles regulating gene expression and maintaining genome stability. Our cryo-EM studies show that within the NuA4/TIP60 complex, the EP400 subunit serves as an architectural scaffold holding the different functional modules in specific positions and giving rise to a novel arrangement of the ARP module. EP400 interacts with the TRRAP subunit using a footprint that overlaps with that of the SAGA acetyltransferase complex, thereby preventing the formation of a hybrid complex. Loss of the TRRAP subunit leads to mislocalization of NuA4/TIP60, resulting in the redistribution of H2A.Z and its acetylation across the genome,emphasizing the dual functionality of NuA4/TIP60 as a single macromolecular assembly.
Project description:The human NuA4/TIP60 co-activator complex, a fusion of the yeast SWR1 and NuA4 complexes, both incorporates the histone variant H2A.Z into nucleosomes and acetylates histones H4/H2A/H2A.Z to play crucial roles regulating gene expression and maintaining genome stability. Our cryo-EM studies show that within the NuA4/TIP60 complex, the EP400 subunit serves as an architectural scaffold holding the different functional modules in specific positions and giving rise to a novel arrangement of the ARP module. EP400 interacts with the TRRAP subunit using a footprint that overlaps with that of the SAGA acetyltransferase complex, thereby preventing the formation of a hybrid complex. Loss of the TRRAP subunit leads to mislocalization of NuA4/TIP60, resulting in the redistribution of H2A.Z and its acetylation across the genome, emphasizing the dual functionality of NuA4/TIP60 as a single macromolecular assembly.
Project description:The human NuA4/TIP60 co-activator complex, a fusion of the yeast SWR1 and NuA4 complexes, both incorporates the histone variant H2A.Z into nucleosomes and acetylates histones H4/H2A/H2A.Z to play crucial roles regulating gene expression and maintaining genome stability. Our cryo-EM studies show that within the NuA4/TIP60 complex, the EP400 subunit serves as an architectural scaffold holding the different functional modules in specific positions and giving rise to a novel arrangement of the ARP module. EP400 interacts with the TRRAP subunit using a footprint that overlaps with that of the SAGA acetyltransferase complex, thereby preventing the formation of a hybrid complex. Loss of the TRRAP subunit leads to mislocalization of NuA4/TIP60, resulting in the redistribution of H2A.Z and its acetylation across the genome, emphasizing the dual functionality of NuA4/TIP60 as a single macromolecular assembly.
Project description:Role of Yng2 PHD and CHD-containing Eaf3 subunits of NuA4 on genome wide histone H4K8 acetylation, NuA4 localization and Pol II distribution
Project description:Although two Enhancer of Polycomb-like proteins, EPL1A and EPL1B (EPL1A/B), are known to be conserved and characteristic subunits of the NuA4-type histone acetyltransferase complex in Arabidopsis thaliana, the biological function of EPL1A/B and the mechanism by which EPL1A/B function in the complex remain unknown. Here, we report that EPL1A/B are required for the histone acetyltransferase activity of the NuA4 complex on the nucleosomal histone H4 in vitro and for the enrichment of histone H4K5 acetylation at thousands of protein-coding genes in vivo. We demonstrate that EPL1A/B are required for linking the NuA4 catalytic subunit HAM1 with accessory subunits in the NuA4 complex. EPL1A/B function redundantly in regulating plant development especially in chlorophyll biosynthesis and de-etiolation. The EPL1A/B-dependent transcription and H4K5Ac are enriched at genes involved in chlorophyll biosynthesis and photosynthesis. We also find that EAF6, another characteristic subunit of the NuA4 complex, contribute to de-etiolation. These results suggest that the Arabidopsis NuA4 complex components function as a whole to mediate histone acetylation and transcriptional activation specifically at light-responsive genes and are critical for photomorphogenesis.
Project description:Although two Enhancer of Polycomb-like proteins, EPL1A and EPL1B (EPL1A/B), are known to be conserved and characteristic subunits of the NuA4-type histone acetyltransferase complex in Arabidopsis thaliana, the biological function of EPL1A/B and the mechanism by which EPL1A/B function in the complex remain unknown. Here, we report that EPL1A/B are required for the histone acetyltransferase activity of the NuA4 complex on the nucleosomal histone H4 in vitro and for the enrichment of histone H4K5 acetylation at thousands of protein-coding genes in vivo. We demonstrate that EPL1A/B are required for linking the NuA4 catalytic subunit HAM1 with accessory subunits in the NuA4 complex. EPL1A/B function redundantly in regulating plant development especially in chlorophyll biosynthesis and de-etiolation. The EPL1A/B-dependent transcription and H4K5Ac are enriched at genes involved in chlorophyll biosynthesis and photosynthesis. We also find that EAF6, another characteristic subunit of the NuA4 complex, contribute to de-etiolation. These results suggest that the Arabidopsis NuA4 complex components function as a whole to mediate histone acetylation and transcriptional activation specifically at light-responsive genes and are critical for photomorphogenesis.
Project description: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.
Project description:Acetylation of histone tails has long been associated with gene activation. Exactly how acetylation regulates gene expression is not fully known. Acetylation events at specific sites or collections of sites on histones elicit distinct outcomes. Here we examine the downstream consequences of histone acetylation by the histone H4 acetyltransferase NuA4 on a genomic scale. Evidence is presented that Bdf1, which is known to bind to acetylated lysine H4 tails in vitro, binds to nucleosomes in vivo and that this binding is dependent upon Esa1, the catalytic subunit of NuA4. Loss of NuA4 results in a coordinate depletion of Bdf1, the transcription complex assembly factor TFIID, and the H2A.Z assembly complex SWR-C at highly acetylated promoter regions. This finding is consistent with known interactions between Bdf1 and TFIID and SWR-C. Loss of Bdf1 results in little or no depletion of TFIID or SWR-C at these promoter regions, possibly due to substitution by the Bdf1 paralog Bdf2. Consistent with this possibility, loss of Bdf1 results in accumulation of Bdf2 at sites normally bound by Bdf1. Together, the findings presented here strengthen the proposed cascade of events whereby nucleosome H4 acetylation by NuA4 at promoters target Bdf1, which then recruits TFIID and SWR-C to assemble the transcription machinery. Keywords: chIP-chip, histone acetylation, transcription factor recruitment