title: mdm-2 gene amplification in 3T3-L1 preadipocytes.
abstract: In this study the regulation of the murine double minute-2 (mdm-2) gene was examined in NIH 3T3-L1 preadipocytes. The 3T3-L1 cell line, under proper conditions, has the capacity to differentiate from fibroblasts into adipocytes [15]. A recent report demonstrated that mdm-2 overexpression could block myogenesis [12]. While examining the regulation of the mdm-2 gene during adipogenesis, it was discovered that 3T3-L1 cells possess a 36-fold elevation of mdm-2 mRNA relative to A31 cells, another immortalized Balb/c 3T3 fibroblast cell line that lacks the capacity to differentiate. Based on Southern blot analysis, the increase in mdm-2 mRNA was the result of a mdm-2 gene amplification. The level of Mdm-2 protein in undifferentiated 3T3-L1 cells was elevated relative to A31 fibroblasts and resulted from translation of mRNA transcripts initiating from the p53-independent P1 promoter. We also examined how mdm-2 and p53 levels changed as undifferentiated fibroblasts converted to adipocytes. While mdm-2 mRNA levels remained elevated, p53 mRNA, protein, and DNA-binding activity decreased. These results suggest that adipogenesis is unaffected by elevated Mdm-2 levels and that the overexpression of mdm-2 mRNA is predominantly p53 independent.
authors.affiliation: Wright State University, School of Medicine, Biochemistry and Molecular Biology Department, Dayton, OH 45435, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Berberich
authors.forename: V
authors.initials: V
authors.lastname: Litteral
authors.forename: L D
authors.initials: LD
authors.lastname: Mayo
authors.forename: D
authors.initials: D
authors.lastname: Tabesh
authors.forename: D
authors.initials: D
authors.lastname: Morris
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005784:Gene Amplification; D005786:Gene Expression Regulation; D051379:Mice; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051736:Proto-Oncogene Proteins c-mdm2; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D016335:Zinc Fingers
chemical_list: D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D003907:Dexamethasone; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D015056:1-Methyl-3-isobutylxanthine