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. 2008 Mar 28;29(6):780-5.
doi: 10.1016/j.molcel.2008.01.019.

MAP kinase-mediated c-fos regulation relies on a histone acetylation relay switch

Amanda O'Donnell  1 , Shen-Hsi Yang, Andrew D Sharrocks
Affiliations

MAP kinase-mediated c-fos regulation relies on a histone acetylation relay switch

Amanda O'Donnell et al. Mol Cell. .

Abstract

Gene activation is often associated with high levels of histone acetylation. Enhanced acetylation levels can promote the recruitment of further chromatin modifying complexes or the basal transcription machinery. Here, we have studied MAP kinase-mediated upregulation of c-fos and uncover a role for histone acetylation in promoting the recruitment of a second transcription factor, NFI. MAP kinase signaling to Elk-1 enhances the net histone acetylase activity associated with the c-fos promoter, which leads to changes in the acetylation state and structure of a promoter-proximal nucleosome, which allows NFI binding. Binding of NFI provides a permissive state for the recruitment of basal machinery and subsequent promoter activation. Our results provide insights into how MAP kinase signaling promotes inducible gene expression; phosphorylation of recipient transcription factors (primary effectors) triggers a HAT relay switch, which facilitates the recruitment of additional transcription factors (secondary effectors) through alteration of the local nucleosomal structure.

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Figures

Figure 1
Figure 1
NFI Is Specifically Recruited to the c-fos Promoter in Response to MAP Kinase Activation (A) Schematic diagram of the c-fos promoter showing the locations of cis-regulatory elements. The shaded oval indicates the siting of a positioned nucleosome. (B) ChIP of NFI bound to the c-fos promoter. HeLa cells were starved in serum-free DMEM (−) or stimulated with either TNFα or PMA for the indicated times (min). Sonicated chromatin was immunoprecipitated with either an anti-NFI antibody or nonspecific IgG. PCR analysis of eluted DNA was performed with oligonucleotides specific for the c-fos promoter (left panels) or egr-1 promoter (right panels). Data are presented as means ± SEM (n ≥ 4) and are the average of at least two independent experiments performed in duplicate.
Figure 2
Figure 2
p300-Mediated Histone Acetylation Promotes Recruitment of NFI to the c-fos Promoter (A) ChIP showing the association of NFI, Elk-1, and acetylated histone H4 with the c-fos promoter upon TSA treatment. HeLa cells were serum starved (−) or starved and treated with TSA for 30 min (+) where indicated. (B) Immunoblot showing the knockdown of p300 protein expression in HeLa cells 48 hr after transfecting with siRNAs targeting p300. (C) ChIP of the c-fos promoter with either an antibody directed toward NFI or normal rabbit IgG. HeLa cells were transfected with siRNA directed toward either p300 or GAPDH and were treated with PMA for 10 min. (D and E) Chromatin accessibility by real-time PCR (CHART-PCR) at the c-fos promoter. Schematic diagram displays the positions of primers (arrows) used for CHART-PCR analysis. HeLa cells were treated with PMA or TSA for 10 min. Where indicated, cells were pretreated with si-p300 before stimulation. Aliquots of isolated nuclei were incubated with increasing amounts of DNase I (0, 1.0, and 2.0 U), and the relative levels of nuclease protection at the nucleosome positioned at the c-fos promoter were measured by real-time PCR. (F) ChIP of the c-fos promoter with either an antibody directed toward total histone H3 or acetylated histone H3 from serum-starved HeLa cells (−) or PMA-treated cells (10 min) (+) as indicated. Data in (A), (C), (D), (E), and (F) are presented as means ± SEM (n ≥ 4, 4, 6, 6, and 4, respectively) and are the average of at least two ([A], [C], and [F]) or three ([D] and [E]) independent experiments performed in duplicate.
Figure 3
Figure 3
NFI Is Involved in MAP Kinase-Mediated Activation of the c-fos Promoter (A) Immunoblot showing the knockdown of Elk-1 protein (top panel) or NFI protein (bottom panel) in HeLa cells 48 hr after transfecting with specifically targeting siRNAs. (B) Luciferase reporter assays with constructs driven by either the c-fos promoter (left panel) or the egr-1 promoter (right panel). HeLa cell lysates were measured for luciferase activity 24 hr after transfection and 6 hr after adding PMA. NFI or Elk-1 was knocked down by siRNA transfection where indicated. (C) Real-time RT-PCR measurement of endogenous c-fos mRNA levels after incubation with PMA at the indicated time points and either control (−) or NFI (+) siRNAs. (D) Schematic diagram illustrating luciferase reporter constructs used in (E) and (F). Crosses indicate the mutated elements in each construct. (E and F) Luciferase reporter assays driven by wild-type c-fos promoter or promoter regions containing mutations within either the SRE (Δets) or the NFI binding site (ΔNFI). HeLa cell lysates were measured for luciferase activity 24 hr after transfection and 6 hr after adding PMA (E) or TSA (F) as indicated. NFI was knocked down by siRNA where indicated (F). Data in (B), (C), (E), and (F) are presented as means ± SD (n = 3) and are representative of two independent experiments performed in triplicate.
Figure 4
Figure 4
Elk-1 and p300-Mediated MAP Kinase-Induced Recruitment of NFI to the c-fos Promoter Represents a Necessary Step in Promoter Activation (A–E) ChIP of endogenous c-fos promoter (A and E) or c-fos-luciferase reporter DNA (B–D) with either an antibody directed toward NFI (A and B), total RNAPII (C and D), or Ser5-phosphorylated RNAPII (E) from serum-starved HeLa cells or cells treated with PMA or TNFα for 10 min. NFI, Elk-1, or p300 was knocked down by siRNA transfection where indicated. (F) Model of proposed sequential activation of the c-fos promoter. MAP kinase pathway activation triggers Elk-1 activation and its associated p300. p300 subsequently acetylates the adjacent nucleosomes, causing a change in nucleosomal structure, NFI recruitment, and the subsequent recruitment and activation of the basal machinery. Data in (A) and (E) are presented as means ± SEM (n ≥ 4) and are the average of at least two independent experiments performed in duplicate. Data in (B), (C), and (D) are presented as means ± SD (n = 3) and are representative of at least two independent experiments performed in triplicate.
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