Transcriptional regulation by the gamma5 subunit of a heterotrimeric G protein during adipogenesis

The adipocyte enhancer-binding protein (AEBP1) is a novel transcriptional repressor with carboxypeptidase activity. A two-hybrid screen was conducted to identify components of AEBP1 that might be important in regulating its activity. The gamma5 subunit of a heterotrimeric G protein was shown to bind specifically to AEBP1 and to attenuate its transcriptional repression activity. Adipogenic stimulation selectively decreased the Ggamma5 level and enhanced the transcriptional repression activity of AEBP1 during mitotic clonal expansion at the onset of adipogenesis. Thus, the actions of Ggamma5 and AEBP1 are directly linked, which could provide the basis for the regulation of transcription at the onset of differentiation. This report shows that a signal-transducing molecule is involved, by direct protein-protein interaction, in the regulation of transcription during adipogenesis.