title: Induction of proto-oncogenes during 3-deazaadenosine-stimulated differentiation of 3T3-L1 fibroblasts to adipocytes: mimicry of insulin action.
abstract: 3-Deazaadenosine (DZA) mimicked the molecular action of insulin in the induction of 3T3-L1 fibroblasts to differentiate into adipocytes. The molecular effects of DZA were compared with insulin, which served as a positive control, on the expression of proto-oncogenes during the initial stage of differentiation of 3T3-L1 fibroblasts. Treatment of confluent 3T3-L1 fibroblasts with DZA or insulin produced a rapid but-transient expression of mRNA for proto-oncogenes c-fos and c-jun within 30-60 min. The mRNA of c-myc increased for 2 h and then decreased 4 h after treatment. Electrophoretic mobility shift assays showed a heightened increase in the appearance of transcription factors AP-1 and AP-2. The increase was detectable as early as 1 h after the treatment with either DZA or insulin and was maintained for 6 h. 3T3-L1 cells stably transfected with the promotor of c-fos linked to a CAT reporter gene showed an increase in CAT activity in response to DZA in a time- and dose-dependent manner. In cells stably transfected with antisense c-fos, neither DZA nor insulin was able to induce a differentiation response. The early transcription of c-fos, c-jun, and c-myc proto-oncogenes and the increased expression of transcription factors AP-1 and AP-2, induced by DZA and insulin, appear to be crucial events in the differentiation of the 3T3-L1 fibroblasts to adipocytes.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Medical College of Virginia, Richmond 23298-0614, USA.
authors.forename: G
authors.initials: G
authors.lastname: Zeng
authors.forename: J R
authors.initials: JR
authors.lastname: Dave
authors.forename: P K
authors.initials: PK
authors.lastname: Chiang
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D017781:Genes, Immediate-Early; D016762:Genes, fos; D016758:Genes, jun; D016259:Genes, myc; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D011519:Proto-Oncogenes; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014372:Tubercidin / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; D007328:Insulin; D018808:Transcription Factor AP-1; D050656:Transcription Factor AP-2; D014157:Transcription Factors; C018258:3-deazaadenosine; D014372:Tubercidin