Analysis of cell cycle arrest in adipocyte differentiation

Manuela Reichert, Dirk Eick

Research output: Contribution to journalArticlepeer-review

103 Scopus citations

Abstract

Confluent 3T3-L1 preadipocytes differentiate to adipocytes in the presence of insulin, dexamethasone, and isobutylmethylxanthine (IDI). A transient increase of DNA synthesis is induced in 3T3-L1 cells 18 h after addition of IDI, followed by an arrest in the G1 phase of the cell cycle. Growth arrested cells express the protooncogene c-myc and the gene for the CCAAT/enhancer binding protein (C/EBPα) between day 2 and 5. While c-Myc is strongly implicated in cell proliferation, C/EBPα is a differentiation-specific transcription factor with anti-proliferative activity. Here we have characterized the cell cycle arrest in differentiating 3T3-L1 cells. Arrested cells express the Cdk inhibitors p21 and p27, but, at the same time, show hyperphosphorylation of Rb and expression of the E2F-regulated thymidine kinase gene. The addition of new serum to arrested cells resulted in cyclin A expression and Cdk2 activity, but not in DNA synthesis. Simian virus 40 large tumor antigen (LTAg) is a potent mitogen. The mutant LTAg-K1, deficient in binding of pocket proteins and unable to induce DNA synthesis in serum-starved 3T3-L1 cells, efficiently induced DIVA synthesis in differentiating 3T3-L1 cells. This indicates that packet proteins are probably not involved in the control of the cell cycle arrest during 3T3-L1 cell differentiation. Our data suggest that the differentiation-specific cell cycle block in 3T3-L1 cells is resistant to high levels of c-Myc, inactivation of pocket proteins, upregulation of cyclin A levels, and Cdk2 activation, but can be abolished by a function of LTAg that is independent of binding to pocket proteins.

Original languageEnglish
Pages (from-to)459-466
Number of pages8
JournalOncogene
Volume18
Issue number2
DOIs
StatePublished - 14 Jan 1999
Externally publishedYes

Keywords

  • 3T3-L1 cells
  • Adipocytes
  • Cell cycle
  • Differentiation
  • Rb
  • SV40 large T antigen

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