Anchorage-dependent transcription of the cyclin A gene.
NIH 3T3 cells cultured in suspension fail to express cyclin A and hence cannot enter S phase and divide. We show that loss of cell adhesion to substratum abrogates cyclin A gene expression by blocking its promoter activity through the E2F site that mediates its cell cycle regulation in adherent cells. In suspended cells, G0-specific E2F complexes remain bound to the cyclin A promoter. Overexpression of cyclin D1 restores cyclin A transcription in suspended cells and rescues them from cell cycle arrest. In suspended cells, cyclin D1 and cyclin E accumulate normally upon serum stimulation, but their associated kinases remain inactive; their substrates, pRb and p107, are not hyperphosphorylated. Concomitantly, the cyclin-dependent kinase inhibitor, p27KIP1, is stabilized. Ectopic expression of p27KIP1 blocks cyclin A promoter activity through its EN binding site. These data suggest that the block to cyclin A transcription in nonadherent NIH 3T3 cells results from stabilization of p27KIP1 and subsequent inactivation of the specific E2F moiety required for its induction.
Schulze
A
A
Forschungschwerpunkt Angewandte Tumorvirologie, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
Zerfass-Thome
K
K
Bergès
J
J
Middendorp
S
S
Jansen-Dürr
P
P
Henglein
B
B
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins; D002448:Cell Adhesion / Q000502:physiology*; D018797:Cell Cycle Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D005786:Gene Expression Regulation; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000502:physiology; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000235:genetics / Q000502:physiology; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016192:Resting Phase, Cell Cycle / Q000235:genetics; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins
C533431:Arid4a protein, mouse; D002352:Carrier Proteins; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D008869:Microtubule-Associated Proteins; D015513:Oncogene Proteins; D011993:Recombinant Fusion Proteins; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27