High affinity binding of H3K14ac through collaboration of bromodomains 2, 4 and 5 is critical for the molecular and tumor suppressor functions of PBRM1

Abstract

Polybromo‐1 ( PBRM 1) is an important tumor suppressor in kidney cancer. It contains six tandem bromodomains ( BD s), which are specialized structures that recognize acetyl‐lysine residues. While BD 2 has been found to bind acetylated histone H3 lysine 14 (H3K14ac), it is not known whether other BD s collaborate with BD 2 to generate strong binding to H3K14ac, and the importance of H3K14ac recognition for the molecular and tumor suppressor function of PBRM 1 is also unknown. We discovered that full‐length PBRM 1, but not its individual BD s, strongly binds H3K14ac. BD s 2, 4, and 5 were found to collaborate to facilitate strong binding to H3K14ac. Quantitative measurement of the interactions between purified BD proteins and H3K14ac or nonacetylated peptides confirmed the tight and specific association of the former. Interestingly, while the structural integrity of BD 4 was found to be required for H3K14ac recognition, the conserved acetyl‐lysine binding site of BD 4 was not. Furthermore, simultaneous point mutations in BD s 2, 4, and 5 prevented recognition of H3K14ac, altered promoter binding and gene expression, and caused PBRM 1 to relocalize to the cytoplasm. In contrast, tumor‐derived point mutations in BD 2 alone lowered PBRM 1's affinity to H3K14ac and also disrupted promoter binding and gene expression without altering cellular localization. Finally, overexpression of PBRM 1 variants containing point mutations in BD s 2, 4, and 5 or BD 2 alone failed to suppress tumor growth in a xenograft model. Taken together, our study demonstrates that BD s 2, 4, and 5 of PBRM 1 collaborate to generate high affinity to H3K14ac and tether PBRM 1 to chromatin. Mutations in BD 2 alone weaken these interactions, and this is sufficient to abolish its molecular and tumor suppressor functions.

BAZ2A association with H3K14ac is required for the transition of prostate cancer cells into a cancer stem-like state

“…The expression analysis of a set of genes that are repressed by BAZ2A and frequently silenced in advanced and poorly differentiated tumors relative to indolent tumors showed the requirement of EP300, one of the writers of H3K14ac. The link of H3K14ac with gene silencing is also consistent with previous studies showing that the transcription regulator ZMYND8, the tumor suppressor PBRM1, and H3K9 methyltransferase SETDB1 can recognize H3K14ac and repress gene transcription (Jurkowska et al, 2017; Li et al, 2016; Liao et al, 2019). The interaction of BAZ2A-BRD with H3K14ac is also of particular interest since H3K14ac was found to be the most prominent histone modification in regulating SNF2H/ISWI nucleosome remodeling and activating only the NoRC complex (Dann et al, 2017).…”

PBRM1 suppresses tumor growth as a novel p53 acetylation reader

“…This result supports the 'histone code' hypothesis and suggests that different combinations of acetylation sites on the p53 CTD can fine-tune p53 transcriptional activity; 3. In agreement with previous report on BD2 and H3K14Ac, 6 adjacent BD(s) collaborates with BD4 to create strong binding to p53 K382Ac. Thus the different BDs might work together like fingers to recognize different KAcs.…”

“…It is also called BAF180, and it targets a SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeler complex to the chromatins though recognizing acetylated lysine 14 on histone H3 (H3K14Ac) via its BD2. 5,6 The components of the SWI/SNF complex have an overall 20% mutation rate in cancers, making it the second most highly mutated entity next to p53. SWI/SNF mutations are also mutually exclusive with TP53 mutations in many cancer types.…”

H3K18Ac as a Marker of Cancer Progression and Potential Target of Anti-Cancer Therapy

“…Interestingly, one BD, BD2, exclusively interacts with H3K14Ac rather than with other histone lysines. BD2 possesses a highly conserved asparagine at position 263 in the aminoacid sequence (Asn263), which seems to be crucial for acetyl-lysine recognition through hydrogen bond formation to acetyl groups [95,96].…”