Overlapping but Distinct Patterns of Histone Acetylation by the Human Coactivators p300 and PCAF within Nucleosomal Substrates

Abstract

A number of transcriptional coactivators possess intrinsic histone acetylase activity, providing a direct link between hyperacetylated chromatin and transcriptional activation. We have determined the core histone residues acetylated in vitro by recombinant p300 and PCAF within mononucleosomes. p300 specifically acetylates all sites of histones H2A and H2B known to be acetylated in bulk chromatin in vivo but preferentially acetylates lysines 14 and 18 of histone H3 and lysines 5 and 8 of histone H4. PCAF primarily acetylates lysine 14 of H3 but also less efficiently acetylates lysine 8 of H4. PCAF in its native form, which is present in a stable multimeric protein complex lacking p300/CBP, primarily acetylates H3 to a monoacetylated form, suggesting that PCAF-associated polypeptides do not alter the substrate specificity. These distinct patterns of acetylation by the p300 and PCAF may contribute to their differential roles in transcriptional regulation.The association of DNA with histones in chromatin antagonizes transcription in vitro (1, 2) and molecular genetic analyses in yeast have demonstrated roles for specific, evolutionarily conserved lysine residues within the N termini of the core histones in transcriptional regulation in vivo (for review see Ref.3). Several studies have demonstrated an enrichment of hyperacetylated histones within transcriptionally active/competent chromatin in vivo (for review see Refs. 4 -7). Strong support for the notion that histone acetylation facilitates transcription is supported by the discovery that transcriptional regulatory proteins, including GCN5 (8, 9), PCAF (10), p300 (11), CBP (12), TAF II 250 (13), and the nuclear hormone receptor coactivators ACTR (14) and SRC-1 (15), possess intrinsic histone acetyltransferase (HAT) 1 activity (for review see Refs. 16 and 17). Moreover, mutational analyses of yeast GCN5 indicate that GCN5 HAT activity in vitro is correlated with histone acetylation at promoter regions and transcriptional activation of target genes in vivo (18,19). These results are further supported by in vitro transcription experiments from nucleosomal templates showing acetylCoA-dependent activation by the GCN5-containing SAGA complex (20). These lines of evidence demonstrate the requirement of the HAT activity of GCN5 for transcriptional activation in a nucleosomal context.

X Box-Like Sequences in the MHC Class II Region Maintain Regulatory Function

“…Thus, with the exception of K18 acetylation, which occurs first, the other histone modifications assayed appear to occur in a similar time frame. The early appearance of H3 K18 acetylation could be attributed to the direct association of CBP/p300 with CIITA because both CBP and p300 are able to generate this modification in vitro (35). Although an increase in K14 was observed at XL-7 in response to IFN-␥, a similar increase at K14 at DRA-X was not observed, highlighting slight differences between the XL-7 and DRA-X.…”

“…The histone H4 code for acetylation of HLA-DRA was previously found to be limited to acetylation of K8 in B cells. H4 K8 acetylation can be catalyzed by CREBbinding protein (CBP)/p300 and P300/CBP-associated factor (35), coactivators shown to interact with CIITA and are necessary for its maximal activity (16,17,36). In IFN-␥-stimulated fibroblasts, additional time-dependent increases observed for histone H4 acetylation at DRA-X included K12 and possibly K5.…”

“…Acetylation at K18 and K27 were constitutively present in CIITApositive B cells at DRA-X, XL4, and XL-7. K18 acetylation can be mediated by CBP and p300 (35). This modification can impact the recruitment of the coactivator-associated arginine methyltransferase (39), which is known to modify histone H3 R17, a modification associated with transcriptional activation.…”

“…Other modifications, including acetylation of K14 and dimethylation of K4, were present in RJ2.2.5 cells, indicating that the X-Y box factors-RFX, CREB and NF-Y-may recruit their own histone modification enzyme complexes to MHC-II promoters. K14 can be acetylated by CBP, p300, and p300/CBP-associated factor (35) and may be recruited to MHC-II X box regions through interactions with phospho-CREB, which interacts directly with CBP/ p300. The enhancement of these latter two modifications in CI-ITA-positive cells B cells may be due to the stabilization of the DNA-bound factors provided by CIITA association (25).…”

Histone acetylation by CBP and p300 at double-strand break sites facilitates SWI/SNF chromatin remodeling and the recruitment of non-homologous end joining factors

“…Impairment of DSB-induced histone H3/H4 acetylation and KU recruitment by ablation of CBP or p300 It is thought that CBP and p300 have HAT activity against histones H3 and H4, as p300 acetylates lysines 14 and 18 of histone H3, and lysines 5 and 8 of histone H4, in vitro (Schiltz et al, 1999;Park et al, 2003;Kouzarides, 2007). In addition, lysine 18 within histone H3 is acetylated by CBP and p300 in vivo (Horwitz et al, 2008).…”