Adipocyte enhancer binding protein (AEBP1), a multifunctional protein involved in adipogenesis.
Date
1997
Authors
Muise, Aleixo Michael.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Adipogenesis is a complex process involving a number of stages each requiring the coordinated expression of numerous genes and the activation or inactivation of numerous proteins. These studies have focused on AEBP1, a protein which is down-regulated during adipogenesis in 3T3 L1 preadipocytes, and have shown that AEBP1 is a preadipocyte-specific negative regulator of the adipogenic aP2 gene.
This study has identified AEBP1 as a DNA-binding protease. Sequence comparisons and kinetic studies using known carboxypeptidase substrates, activators, and inhibitors have characterized AEBP1 as a member of the regulatory-type B-like carboxypeptidase family. The C-terminal region of AEBP1 has been shown to bind to the AE-1 promoter region of the aP2 gene. Once AEBP1 is bound to DNA, an inherent carboxypeptidase activity is enhanced. This enhanced protease activity is required for AEBP1 to repress transcription of the aP2 gene by an active repression mechanism. This thesis has shown that the DNA-binding, the enzymatic activity, and the transcription repression function of AEBP1 are correlated, and strongly suggests that the DNA-bound AEBP1 uses its protease function to repress transcription.
Two-hybrid interaction studies have shown that AEBP1 interacts with heat shock protein 27 (HSP27), high mobility group 2 (HMG-2), and the G$\gamma$5 subunit of a trimeric G protein. AEBP1 forms complexes with the G$\beta\gamma5$ heterodimerin coimmunoprecipitation experiments. The in vitro interaction between AEBP1 and G$\gamma5$ prevents AEBP1 from binding DNA, which inhibits the transcription repression function of AEBP1.
Furthermore, AEBP1 forms complexes in coimmunoprecipitation and gel filtration studies with both the active and inactive forms of the mitogen-activated protein kinase (MAPK). In vitro experiments have shown that MAPK phosphorylates AEBP1 in the C terminus. This in vitro interaction between AEBP1 and MAPK enhances the DNA-binding ability of AEBP1 and protects MAPK from inactivation by phosphatases.
In sum, AEBP1 appears to function as a negative transcriptional regulator of at least one adipogenic induced gene and may also be mediated by putative signaling pathways.
Thesis (Ph.D.)--Dalhousie University (Canada), 1997.
This study has identified AEBP1 as a DNA-binding protease. Sequence comparisons and kinetic studies using known carboxypeptidase substrates, activators, and inhibitors have characterized AEBP1 as a member of the regulatory-type B-like carboxypeptidase family. The C-terminal region of AEBP1 has been shown to bind to the AE-1 promoter region of the aP2 gene. Once AEBP1 is bound to DNA, an inherent carboxypeptidase activity is enhanced. This enhanced protease activity is required for AEBP1 to repress transcription of the aP2 gene by an active repression mechanism. This thesis has shown that the DNA-binding, the enzymatic activity, and the transcription repression function of AEBP1 are correlated, and strongly suggests that the DNA-bound AEBP1 uses its protease function to repress transcription.
Two-hybrid interaction studies have shown that AEBP1 interacts with heat shock protein 27 (HSP27), high mobility group 2 (HMG-2), and the G$\gamma$5 subunit of a trimeric G protein. AEBP1 forms complexes with the G$\beta\gamma5$ heterodimerin coimmunoprecipitation experiments. The in vitro interaction between AEBP1 and G$\gamma5$ prevents AEBP1 from binding DNA, which inhibits the transcription repression function of AEBP1.
Furthermore, AEBP1 forms complexes in coimmunoprecipitation and gel filtration studies with both the active and inactive forms of the mitogen-activated protein kinase (MAPK). In vitro experiments have shown that MAPK phosphorylates AEBP1 in the C terminus. This in vitro interaction between AEBP1 and MAPK enhances the DNA-binding ability of AEBP1 and protects MAPK from inactivation by phosphatases.
In sum, AEBP1 appears to function as a negative transcriptional regulator of at least one adipogenic induced gene and may also be mediated by putative signaling pathways.
Thesis (Ph.D.)--Dalhousie University (Canada), 1997.
Keywords
Biology, Molecular., Biology, Genetics., Chemistry, Biochemistry.