Human ARF binds E2F1 and inhibits its transcriptional activity.
The INK4a/ARF locus which is frequently inactivated in human tumours encodes two different tumour suppressive proteins, p16(INK4a) and ARF. p16(INK4a) is a major component of the RB pathway. ARF is part of an ARF-mdm2-p53 network that exerts a negative control on hyperproliferative signals emanating from oncogenic stimuli. Among these is the transcription factor E2F1, a final effector of the RB pathway, that induces ARF expression. Recent data suggest that ARF function is not restricted to the p53 pathway. However, ARF target(s) implicated in this p53-independent function remains to be identified. We show that ARF is able to inhibit the proliferation of human cell lines independently of their p53 status. In this context, we demonstrate that ARF interacts physically with E2F1 and inhibits its transcriptional activity. Moreover, we show that mdm2 is required for the modulation of E2F1 activity by ARF. Beside the well-known p53 and mdm2 partners, these results identify E2F1 as a new ARF target. Thus, ARF can be viewed as a dual-acting tumour suppressor protein in both the p53 and RB pathways, further emphasizing its role in tumour surveillance.
Eymin
B
B
Groupe de recherche sur le cancer du poumon, INSERM EMI 9924, Institut Albert Bonniot, 38706 La Tronche Cedex, France.
Karayan
L
L
Séité
P
P
Brambilla
C
C
Brambilla
E
E
Larsen
C J
CJ
Gazzéri
S
S
D020727:ADP-Ribosylation Factors / Q000378:metabolism* / Q000494:pharmacology*; D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000235:genetics; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D003114:Colony-Forming Units Assay; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005091:Exons / Q000502:physiology; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D016296:Mutagenesis / Q000502:physiology; D009687:Nuclear Proteins; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000378:metabolism*
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D005982:Glutathione Transferase; D020727:ADP-Ribosylation Factors