Molecular cloning, characterization and functional studies of P113: A transcription factor that regulates the expression of acetyl-CoA carboxylase
Abstract
The transcription of acetyl-CoA carboxylase (ACC) gene is driven by two promoters, designated as PI and PII. The activity of PII is repressed by tumor necrosis factor-$\alpha$ (TNF-$\alpha)$ in a mouse preadipocyte line 30A5. A 30 bp fragment ($-$388/$-$359) TNF-response element (TRE) was identified on PII. The TRE contains a 7 bp sequence (-GCCTGCC-) that is highly homologous to a consensus TNF response element (-GCC(A/T)GGC). In this study, the cDNAs encoding TNFRE-binding proteins were isolated. The full-length mouse cDNA, named P113, encodes a 113.4 kd protein that is 83% and 89% identical to HIP116/HLTF (human) and RUSH-1$\alpha$ (rabbit), respectively. P113 mRNA is expressed in different rat tissues at different levels and different sizes, suggesting that P113 is functioning in a tissue-specific fashion. The expression pattern of P113 is significantly different from that of its human counterpart, HLTF, implying they may have different in vivo functions and regulatory mechanisms. P113 contains seven motifs conserved in many DNA-dependent ATPases/helicases, a characteristic feature of the SNF2/SWI2 protein family. The affinity purified P113 has a ATPase activity that is stimulated by DNA in a sequence specific manner. A RING finger motif was also found in P113. These structural and functional features indicated that P113 is a new member of the SNF2/SWI2 protein family and the RING finger protein family. P113 binds specifically to a important regulatory fragment ($-$88/$-$59) of PAI-1 promoter and the 30 bp TRE of ACC PII. It is demonstrated in this study that P113 is involved in the transcription regulation of both PAI-1 gene and ACC gene. Mutation of the 7 bp TNFRE in the 30 bp TRE partially abolished both the binding of P113 to the 30 bp TRE and the transactivation of ACC PII by P113, indicating P113 is a transcription factor with relative sequence specificity. In the transient transfection system, the ATPase activity is not required for the transactivation function of P113. This result suggested that the mechanism of P113 might be different from the other SNF2/SWI2 proteins. No direct evidence was obtained concerning the relationship between P113 and the regulation of ACC expression by TNF.
Degree
Ph.D.
Advisors
Kim, Purdue University.
Subject Area
Molecular biology
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