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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    • "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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    • "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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