E2F-mediated growth regulation requires transcription factor cooperation.
Previous studies have indicated that the presence of an E2F site is not sufficient for G1/S phase transcriptional regulation. For example, the E2F sites in the E2F1 promoter are necessary, but not sufficient, to mediate differential promoter activity in G0 and S phase. We have now utilized the E2F1 minimal promoter to test several hypotheses that could account for these observations. To test the hypothesis that G1/S phase regulation is achieved via E2F-mediated repression of a strong promoter, a variety of transactivation domains were brought to the E2F1 minimal promoter. Although many of these factors caused increased promoter activity, growth regulation was not observed, suggesting that a general repression model is incorrect. However, constructs having CCAAT or YY1 sites or certain GC boxes cloned upstream of the E2F1 minimal promoter displayed E2F site-dependent regulation. Further analysis of the promoter activity suggested that E2F requires cooperation with another factor to activate transcription in S phase. However, we found that the requirement for E2F to cooperate with additional factors to achieve growth regulation could be relieved by bringing the E2F1 activation domain to the promoter via a Gal4 DNA binding domain. Our results suggest a model that explains why some, but not all, promoters that contain E2F sites display growth regulation.
van Ginkel
P R
PR
McArdle Laboratory for Cancer Research, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA.
Hsiao
K M
KM
Schjerven
H
H
Farnham
P J
PJ
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D016384:Consensus Sequence; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D017930:Genes, Reporter; D006706:Homeostasis; D051379:Mice; D008954:Models, Biological; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D016192:Resting Phase, Cell Cycle; D056465:Retinoblastoma-Binding Protein 1; D016196:S Phase; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
C533431:Arid4a protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493754:E2f1 protein, mouse; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors