Acetylation of HMG I(Y) by CBP Turns off IFNβ Expression by Disrupting the Enhanceosome

Abstract

The transcriptional coactivators CBP and P/CAF are required for activation of transcription from the IFN beta enhanceosome. We show that CBP and P/CAF acetylate HMG I(Y), the essential architectural component required for enhanceosome assembly, at distinct lysine residues, causing distinct effects on transcription. Thus, in the context of the enhanceosome, acetylation of HMG I by CBP, but not by P/CAF, leads to enhanceosome destabilization and disassembly. We demonstrate that acetylation of HMG I(Y) by CBP is essential for turning off IFN beta gene expression. Finally, we show that the acetyltransferase activities of CBP and P/CAF modulate both the strength of the transcriptional response and the kinetics of virus-dependent activation of the IFN beta gene.

A quantitative study on the in vitro and in vivo acetylation of high mobility group A1 proteins

“…LC-MS/MS results allowed us to detect both the acetylated (SSQPLASK 14 QEK) and unacetylated peptides (SSQPLASK 14 QEK and SSQPLASK 14 ) containing Lys-14 (spectra not shown), which is consistent with our previous°in°vivo°study° [28].°However,°we°were°not°able°to identify any peptides containing Lys-64 or Lys-70, and these two residues were previously shown to be acetylated°by°CBP°and°PCAF,°respectively° [27].…”

“…Second, p300 and PCAF acetylated the HMGA1 proteins in vitro with different profiles of site specificity. Previous in vitro acetylation assay° [27]°suggested°that,°except°for°the°major°acetyla-tion sites of Lys-64 induced by CBP and Lys-70 induced by PCAF, many other lysine residues can also be acetylated, especially by PCAF. We, however, detected only°five°acetylation°sites,°which°might°be°attributed°to the fact that protein substrates, rather than peptide substrates, were employed to examine the site preferences of histone acetyltransferases in the present study.…”

“…CBP and its closely related p300 were discovered as transcriptional coactivators for a number of sequencespecific factors that integrate diverse signaling pathways° [48].°These°two°proteins°and°their°associated factor PCAF have intrinsic histone acetyltransferase activity° [49,°50].°They°can°induce°the°acetylation°of lysine residues not only in histone proteins but also in many other transcriptional factors including TFIIE and TFIIF; thus, they are also known as factor acetyltransferases° [51].°In°addition,°p300°has°been°implicated°in DNA repair processes because of its involvement in the acetylation of many DNA repair-enzymes such as flap endonuclease 1 (FEN1), DNA polymerase ␤ (Pol␤), G/T mismatch-specific DNA glycosylase (TDG) and DNA glycosylases°NEIL2°and°OGG1° [52][53][54][55].°It°has°been reported that p300 could acetylate both HMGN1 (formerly known as HMG-14) and HMGN2 (formerly known as HMG-17) at multiple sites, whereas PCAF could acetylate only HMGN2 with Lys-2 being the predominant°acetylation°site° [56,°57].°Moreover,°Mun-shi°et°al.° [27]°showed°that°the°HAT°domains°of°both CBP and PCAF could acetylate HMGA1a proteins as efficiently as histones in vitro and the preferential acetylation sites were Lys-64 and Lys-70, respectively, according to the in vitro acetylation of peptide segments of HMGA1 proteins.…”

“…In this respect, Lys-64 and Lys-70 in HMGA1a protein can be acetylated by CBP (CREB-binding protein) and PCAF (p300/CBP-associated factor), respectively [26,27]. In addition, the acetylation at these two sites conferred distinct biological outcomes; the acetylation of Lys-64 destabilized the enhanceosome, whereas the acetylation of Lys-70 potentiated transcription of interferon-␤ gene by stabilizing the enhanceosome and preventing the acetylation of HMGA1a by CBP [26,27]. Moreover, multiple acetylation sites in HMGA1 proteins from MCF-7 human breast cancer cells have been suggested, though the assignment of these modifications to specific lysine residues was not made [8].…”

Sirtuins, nuclear hormone receptor acetylation and transcriptional regulation

“…Several transcription factors, including the nuclear hormone receptors (estrogen receptor α (ERα), androgen receptor (AR), thyroid hormone receptor β (TRβ) and glucocorticoid receptor (GR)), p53 [11,12], GATA-1 [13], GATA-2 [14], GATA-3 [15], EKLF [16] and HMG proteins [17], are altered by acetylation. Acetylation of transcription factors results in altered binding to DNA, transcriptional activation, protein stability, subcellular localization and altered protein-protein interactions.…”