The ZZ domain of p300 mediates specificity of the adjacent HAT domain for histone H3

Abstract

Human p300 is a transcriptional co-activator and a major acetyltransferase that acetylates histones and other proteins facilitating gene transcription. The activity of p300 relies on the fine-tuned interactome that involves a dozen p300 domains and hundreds of binding partners and links p300 to a wide range of vital signaling events. Here, we report a novel function of the ZZ-type zinc finger (ZZ) of p300 as a reader of histone H3. We show that the ZZ domain and acetyllysine-recognizing bromodomain of p300 play critical roles in modulating p300 enzymatic activity and its association with chromatin. The acetyllysine binding function of bromodomain is essential for acetylation of histones H3 and H4, whereas interaction of the ZZ domain with H3 promotes selective acetylation of the histone H3K27 and H3K18 sites.

The ZZ domain as a new epigenetic reader and a degradation signal sensor

“…A 9 µM binding affinity of the p300 ZZ domain to the unmodified H3 peptide, which is in the range of binding affinities of other histone-recognizing modules, further confirms that this domain is a novel epigenetic reader (Taverna et al 2007; Musselman et al 2012; Andrews et al 2016). The crystal structure of the p300 ZZ domain-H3 complex reveals a unique H3-binding mechanism that differs from the binding mechanisms of other known H3-specific readers (Zhang, Xue, et al 2018). The N-terminal residues of histone H3, Ala1-Gln5, make extensive intermolecular contacts with the ZZ domain, pairing with the β1-stand of the ZZ domain (Figure 2(a)).…”

“…Pull-down assays using 16 ZZ domains derived from 15 human proteins reveal that nine ZZ domains are capable of binding to histone H3 tail (Mi et al 2018). Specifically, the ZZ domain of p300 was shown to recognize unmodified histone H3, whereas the ZZ domain of ZZZ3 selects for the histone H3 tail acetylated on lysine 4 (H3K4ac) (Mi et al 2018; Zhang, Xue, et al 2018). The ZZ domain of HERC2 was defined as a SUMO binding module that promotes protein interactions and SUMOylation (Danielsen et al 2012).…”

“…Using histone peptides containing various PTMs in immunoprecipitation and NMR assays, Zhang et al have recently shown that the ZZ domain of p300 binds to the N-terminus of histone H3, and acetylation or methylation of H3K4 does not affect this interaction (Zhang, Xue, et al 2018). A 9 µM binding affinity of the p300 ZZ domain to the unmodified H3 peptide, which is in the range of binding affinities of other histone-recognizing modules, further confirms that this domain is a novel epigenetic reader (Taverna et al 2007; Musselman et al 2012; Andrews et al 2016).…”

“…Most of histone readers recruit or stabilize their host proteins at specific chromatin regions, and the ZZ domain is not an exception. The robust association of the p300 fragment containing bromodomain, the RING and PHD fingers, the HAT domain and the ZZ domain (hereafter referred to as BRPHZ) with chromatin is shown to depend on concurrent interactions of the ZZ domain with H3 and of bromodomain with acetylated histones (Zhang, Xue, et al 2018). Importantly, the H3-binding function of the ZZ domain is found to be vital for p300 to specifically acetylate H3K18 and H3K27 sites in vitro and in vivo.…”

“…The family of epigenetic readers is growing fast and currently contains ~30 members that target unmodified histone tails or histone PTMs either specifically or promiscuously and modulate chromatin function, structure and dynamics (Taverna et al 2007; Kutateladze 2011; Musselman et al 2012; Andrews et al 2016). The most recent addition to the family of epigenetic readers is the ZZ-type zinc finger (ZZ) domain that has been found to recognize unmodified and acetylated histone H3 tail (Mi et al 2018; Zhang, Xue, et al 2018), and some associate with nonhistone substrates.…”