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Interaction between Rb and C/EBPβ fails to recruit HDAC during the hypoxic repression of adipogenesis
Author(s) -
Park YoungKwon,
Cho Heesang,
Park Hyunsung
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.lb101-b
Subject(s) - adipogenesis , transactivation , chemistry , transcription factor , sodium butyrate , retinoblastoma protein , ccaat enhancer binding proteins , psychological repression , e2f , transcription (linguistics) , histone deacetylase , microbiology and biotechnology , histone , cell cycle , biology , dna , biochemistry , cell , nuclear protein , gene , gene expression , linguistics , philosophy
Adipogenesis is triggered by the sequential activation of key adipogenic transcription factors such as C/EBPβ, C/EBPα and PPARγ. We find that hypoxia reduces the transactivity of C/EBPβ but not its amount. C/EBPβ gains its DNA binding and transactivation ability after preadipocytes enter the G1/S transition. Hypoxic preadipocytes highly express p27, the cell cycle kinase inhibitor. p27 blocks the G1/S transition by inhibiting phosphorylation of Retinoblastoma(Rb) protein. The findings that Rb activates the adipogenesis by direct interaction with C/EBPs, and that unphosphorylated Rb blocks the activity of E2F transcription factor by mediating the recruitment of Histone deacetylase(HDAC) lead us to investigate whether unphosphorylated Rb interacts with C/EBPβ, leading to recruitment of HDAC. Our results showed that Rb interacts with C/EBPβ but C/EBPβ‐bound Rb fails to recruit HDAC. It suggests that Rb regulates the transactivity of C/EBPβ not by mediating the indirect interaction between C/EBPβ and HDAC. Consistently with this idea, HDAC inhibitor, sodium butyrate fails to recover the adipogenesis of hypoxic preadipocytes. [This work was supported by a grant (R01‐2002‐000‐00242‐0) from KOSEF]