Endogenous CCAAT/enhancer binding protein and p300 are both regulated by growth hormone to mediate transcriptional activation

Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0622, USA.
Molecular Endocrinology (Impact Factor: 4.02). 09/2005; 19(8):2175-86. DOI: 10.1210/me.2004-0502
Source: PubMed


The regulation of c-fos transcription by GH involves multiple factors, including CCAAT/enhancer binding protein (C/EBP) beta. Knockdown of C/EBPbeta by RNA interference prevents stimulation of endogenous c-fos mRNA by GH, indicating a key role for C/EBPbeta in GH-stimulated c-fos transcription. GH rapidly increases the occupancy of both endogenous C/EBPbeta and p300 on the c-fos promoter in 3T3-F442A preadipocytes as indicated by chromatin immunoprecipitation. The transient occupancy of p300 on c-fos and the presence of p300 in the anti-C/EBPbeta immunoprecipitate coincide with the transient increase in c-fos transcription with GH, suggesting that a nuclear complex containing both p300 and C/EBPbeta occupies the c-fos promoter in response to GH. Expression of p300 with C/EBPbeta markedly increases c-fos promoter activity when neither alone is effective, indicating that p300 coactivates C/EBPbeta-mediated c-fos promoter activation. Such coactivation can determine a baseline for c-fos activation by GH. Furthermore, the occupancy of phosphorylated murine C/EBPbeta (T188) on c-fos upon GH treatment is simultaneous with increased occupancy by p300, suggesting that phospho-C/EBPbeta recruits p300 in response to GH. Thus, endogenous C/EBPbeta and p300 on c-fos are dynamically regulated by GH to determine transcriptional activation. Phosphorylated C/EBPbeta and p300 appear to function as part of a regulated complex that mediates GH-stimulated transcription.

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Available from: Jeffrey S Huo, Jun 17, 2014
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    • "Asterisks (*) indicate responses to GH that are statistically significant (P < 0.05). lated by GH (Cui et al., 2005, 2011). The role of p300 as a coactivator of STAT5 has been well described (Litterst et al., 2005; Paulson et al., 1999; Pfitzner et al., 1998). "
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    ABSTRACT: Expression of the Growth Hormone (GH)-stimulated gene Socs2 (Suppressor Of Cytokine Signaling 2) is mediated by the transcription activator STAT5 (Signal Transducer and Activator of Transcription 5) and the transcription repressor BCL6 (B-cell lymphoma 6). ChIP-Sequencing identified Cish (Cytokine-inducible SH2-containing protein) and Bcl6 as having similar patterns of reciprocal occupancy by BCL6 and STAT5 in response to GH, though GH stimulates Cish and inhibits Bcl6 expression. The co-activator p300 occupied Socs2, Cish and Bcl6 promoters, and enhanced STAT5-mediated activation of Socs2 and Cish. In contrast, on Bcl6, p300 functioned as a repressor and inhibited in conjunction with STAT5 or BCL6. The co-repressor HDAC3 (Histone deacetylase 3) inhibited the Socs2, Cish and Bcl6 promoters in the presence of STAT5. Thus transcriptional outcomes on GH-regulated genes occupied by BCL6 and STAT5 are determined in a promoter-specific fashion by co-regulatory proteins which mediate the distinction between activating and repressive transcription factors.
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    • "DS - PAGE , and immunoblotted as previously described ( Hodge et al . , 1998 ) . Bands on immunoblots were visualized and quantified using IRDye 700 - coupled anti - mouse IgG ( 1 : 10 , 000 ) or IRDye 800 - coupled anti - rabbit IgG ( 1 : 10 , 000 ) on an Odyssey infrared scanning system ( LI - COR Inc . , Lincoln , NE ) as previously described ( Cui et al . , 2005 ) . Molecular weight was estimated using Kaleidoscope protein molecular weight standard ( Biorad ) or Magic Mark XP Western Standard ( Invitrogen ) . For analysis of deacetylation , 293T cells ( 100 mm plates ) were transfected with plasmids for WT HA - C / EBP␤ or K39R HA - C / EBP␤ ( 4 ␮g ) , p300 ( 2 ␮g ) , and the indicated HDAC1 ( "
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    ABSTRACT: The transcription factor CCAAT/enhancer binding protein beta (C/EBPbeta) contains multiple acetylation sites, including lysine (K) 39. Mutation of C/EBPbeta at K39, an acetylation site in the transcriptional activation domain, impairs transcription of C/EBPbeta target genes in a dominant-negative fashion. Further, K39 of C/EBPbeta can be deacetylated by HDAC1, and HDAC1 may decrease C/EBPbeta-mediated transcription, suggesting that acetylation of C/EBPbeta at K39 is dynamically regulated in mediating gene transcription. Acetylation of endogenous C/EBPbeta at K39 is detected in adipose tissue, and also occurs in 3T3-L1 cells undergoing adipocyte conversion. In addition, mutation of K39 in C/EBPbeta impairs activation of its target genes encoding C/EBPalpha and PPARgamma, essential mediators of adipogenesis, as well as adipocyte genes for leptin and Glut4. These findings suggest that acetylation of C/EBPbeta at K39 is an important and dynamic regulatory event that contributes to its ability to transactivate target genes, including those associated with adipogenesis and adipocyte function.
    Molecular and Cellular Endocrinology 08/2008; 289(1-2):94-101. DOI:10.1016/j.mce.2008.03.009 · 4.41 Impact Factor
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    • "For example, MAP kinase-mediated phosphorylation results in nuclear redistribution of C/EBPb, allowing for spatial control of gene transcription (Piwien-Pilipuk et al., 2003). In addition, phosphorylation of C/EBPb results in the recruitment of p300 and other nuclear proteins, resulting in the formation of an enhanceosome (Schwartz et al., 2003; Cui et al., 2005). Recruitment of p300 by C/EBPb may result in acetylation of C/EBPb, providing another mechanism by which transcriptional activity is influenced. "
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