Recognition of Unmodified Histone H3 by the First PHD Finger of Bromodomain-PHD Finger Protein 2 Provides Insights into the Regulation of Histone Acetyltransferases Monocytic Leukemic Zinc-finger Protein (MOZ) and MOZ-related factor (MORF)

Abstract

MOZ (monocytic leukemic zinc-finger protein) and MORF (MOZ-related factor) are histone acetyltransferases important for HOX gene expression as well as embryo and postnatal development. They form complexes with other regulatory subunits through the scaffold proteins BRPF1/2/3 (bromodomain-PHD (plant homeodomain) finger proteins 1, 2, or 3). BRPF proteins have multiple domains, including two PHD fingers, for potential interactions with histones. Here we show that the first PHD finger of BRPF2 specifically recognizes the N-terminal tail of unmodified histone H3 (unH3) and report the solution structures of this PHD finger both free and in complex with the unH3 peptide. Structural analysis revealed that the unH3 peptide forms a third antiparallel ␤-strand that pairs with the PHD1 two-stranded antiparallel ␤-sheet. The binding specificity was determined primarily through the recognition of arginine 2 and lysine 4 of the unH3 by conserved aspartic acids of PHD1 and of threonine 6 of the unH3 by a conserved asparagine. Isothermal titration calorimetry and NMR assays showed that post-translational modifications such as H3R2me2as, H3T3ph, H3K4me, H3K4ac, and H3T6ph antagonized the interaction between histone H3 and PHD1. Furthermore, histone binding by PHD1 was important for BRPF2 to localize to the HOXA9 locus in vivo. PHD1 is highly conserved in yeast NuA3 and other histone acetyltransferase complexes, so the results reported here also shed light on the function and regulation of these complexes.Histone acetyltransferases (HATs) 3 are enzymes that catalyze the transfer of an acetyl group from acetyl-CoA to the ⑀-amino groups of lysine on histones, which results in important regulatory effects in chromatin structure and assembly as well as gene expression. HATs are highly diverse and generally form multiprotein complexes. Different HAT complexes are composed of various unique subunits, and the combination of these subunits contributes to the unique features of each HAT complex (1).MOZ (monocytic leukemic zinc-finger protein) and MORF (MOZ-related factor), a pair of large HATs of the MYST (Moz, Ybf2/Sas3, Sas2, Tip60) family, are important for hematopoiesis, skeletogenesis, neurogenesis, and other developmental processes, and they also have been implicated in leukemogenic and other tumorigenic progressions (2). A recent study in mice embryos reported that MOZ is required for normal levels of spatially correct Hox gene expression and for correct body segment identity. MOZ is specifically required for the H3K9 acetylation of active Hox gene loci (3). MOZ is also required for the maintenance of hematopoietic stem cells and plays a role in the differentiation of erythroid and myeloid cells (4). By contrast, MORF is required for the maintenance of undifferentiated neuronal progenitors and for adult neural stem cell self-renewal and neuronal differentiation (5). MOZ and MORF genes are often translocated in acute myeloid leukemia cells, producing either fusion proteins with CBP (cAMP-response elementbinding protein (CREB)-bind...

Combinatorial readout of unmodified H3R2 and acetylated H3K14 by the tandem PHD finger of MOZ reveals a regulatory mechanism for HOXA9 transcription

“…Several epigenetic readers are included in the complex, such as the ING5 PHD finger recognizing H3K4me3 (Champagne et al 2008), BRPF1 PWWP recognizing H3K36me3 (Vezzoli et al 2010), the BRPF2 PHD finger 1 recognizing H3K4me0 (Qin et al 2011), and the BRPF bromodomain recognizing acetylated histones and other proteins (Zeng and Zhou 2002). Our present work showed that unmodified R2 and acetylated K14 of the H3 tail can be specifically read by the tandem PHD finger of MOZ.…”

“…7A; Champagne et al 2008). After that, the first PHD finger of the BRPF protein binds H3K4me0 (Qin et al 2011), and the tandem PHD finger of MOZ binds to unmodified H3R2, stabilizing the complex to perform acetyl transfer reactions against histone H3 (Fig. 7B).…”

Exchange of associated factors directs a switch in HBO1 acetyltransferase histone tail specificity

“…We previously demonstrated that the JADE1L scaffold subunit found within the HBO1 HAT complex contains a PZP domain that recognizes unmethylated H3K4 (Saksouk et al 2009;Avvakumov et al 2012). Importantly, the first PHD domain of BRPF2 (also known as Brd1, a paralog of BRPF1) has recently been shown to bind the N-terminal tail of histone H3 (Qin et al 2011;Liu et al 2012). As BRPF1 also contains a similar tandem PHD finger module, we characterized its affinity for histone marks.…”

Decreased MORF leads to prolonged endoplasmic reticulum stress in periodontitis-associated chronic inflammation

“…The inflammatory microenvironment may regulate the expression of MORF by epigenetic modification or through the loop, in which paracrine factors of MSCs inhibit MORF expression. In addition, MORF possesses additional modules (such as PHD fingers), 49 which may mediate its binding to other transcription factors in UPR genes. This evidence illustrates the possibility that MORF may function with other transcription factors and act as a transcriptional coregulator.…”