Endogenous CCAAT/enhancer binding protein beta and p300 are both regulated by growth hormone to mediate transcriptional activation.
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.
Cui
Tracy Xiao
TX
Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0622, USA.
Piwien-Pilipuk
Graciela
G
Huo
Jeffrey S
JS
Kaplani
Julianne
J
Kwok
Roland
R
Schwartz
Jessica
J
D017667:Adipocytes / Q000166:cytology; D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D016466:CHO Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D006224:Cricetinae; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000378:metabolism*; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D022782:CCAAT-Enhancer-Binding Protein-beta; D016760:Proto-Oncogene Proteins c-fos; D013006:Growth Hormone; D008156:Luciferases