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

• Autores: Cui, Tracy Xiao; Piwien Pilipuk, Graciela; Huo, Jeffrey S.; Kaplani, Julianne; Kwok, Roland; Schwartz, Jessica
• Año de publicación: 2005
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: C/Ebpbeta; P300; Gh
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

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/EBP beta 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.
Fil: Cui, Tracy Xiao. University of Michigan; Estados Unidos
Fil: Piwien Pilipuk, Graciela. University of Michigan; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Huo, Jeffrey S.. University of Michigan; Estados Unidos
Fil: Kaplani, Julianne. University of Michigan; Estados Unidos
Fil: Kwok, Roland. University of Michigan; Estados Unidos
Fil: Schwartz, Jessica. University of Michigan; Estados Unidos