A eukaryotic transcriptional represser with carboxypeptidase activity

Abstract

Adipocyte differentiation involves the transcriptional activation of several genes in triglyceride metabolism, including the adipose P2 (aP2 or 422) gene that encodes the adipocyte lipid-binding protein ALBP. Within the mouse aP2 promoter region, the AE-1 sequence functions as either a positive or a negative element in the regulation of aP2 gene expression. The AE-1 sequence is the binding site for the positive murine (3T3) adipocyte factor C/EBP-alpha, several human preadipocyte factors, and a 3T3 preadipocyte factor(s) that has been implicated as a repressor of aP2 gene expression. Here we report the cloning of new complementary DNAs that encode the 3T3 preadipocyte factor (termed AEBP1) and demonstrate that AEBP1 expression is abolished during adipocyte differentiation. Furthermore, we show that an activity of a carboxypeptidase associated with AEBP1 is important in the transcriptional repression function of AEBP1. Thus AEBP1 might represent a new type of transcription factor that regulates transcription by cleavage of factors involved in transcription.

Central (ICV) leptin injection increases bone formation, bone mineral density, muscle mass, serum IGF-1, and the expression of osteogenic genes in leptin-deficient ob/ob mice

“…(12,(42)(43)(44) The AEBP1 protein plays an important role in adipogenesis by modulating the differentiation of preadipocytes, and Aepb1 gene expression is increased in proliferating preadipocytes. (42,43) DLK1 is a regulator of mesenchymal cell differentiation. (44) The decreased expression of Dlk1 in bone marrow of mice treated ICV with the high dose of leptin may have been associated with increased differentiation of mesenchymal stem cells to osteoblasts.…”

Enzymic characterization of a novel member of the regulatory B-like carboxypeptidase with transcriptional repression function: stimulation of enzymic activity by its target DNA

“…The AEBP1 cDNA insert [6], cloned into the vector pET-16b, was transformed into DH5α cells, and transformants were screened by isolation of plasmid DNA followed by endonuclease restriction digests to identify positive clones. Once clones were identified, they were transformed into DE3 cells.…”

“…As these differences are thought to determine the location of the CP in the cell, and there are also variations in the C-and N-terminus of the protease region of AEBP1, which has an extra 165 amino acids in the N-terminus and 168 amino acids in the C-terminus, these additional amino acids may contribute to a multifunctional role for AEBP1 within the cell (S.-W. Kim, A. Muise and H.-S. Ro, unpublished work, [6,17]). Although the mechanism by which CP-B-like proteases remove C-terminal basic amino acids is unknown, comparison of the Zn# + -binding residues, substratebinding residues and the catalytic residues with similar residues in CP-A [18] may give an insight into possible mechanisms of the CP-B-like protease.…”

“…We have defined previously a cis-controlling element, adipocyte enhancer 1 (AE-1) and its trans-acting factors, which include the positive murine (3T3) adipocyte factor, CCAAT\enhancer binding protein α [4], human preadipocyte factors [5] and the negative 3T3 preadipocyte factor, adipocyte-enhancer binding protein (AEBP) 1 [6], which are involved in either positive or negative regulation of aP2 gene expression. Past work has focused on the transcriptional repressor factor AEBP1.…”

“…The above examples demonstrate the diverse functions of the regulatory B-like CPs in several cell functions, including differentiation and cell signalling.The main body of AEBP1 contains a domain with a high degree of similarity to the family of B-like CPs [6]. Sequence comparisons suggested that AEBP1 may function similarly to the CP-B-like proteases.…”