Inhibition of cyclin D1 kinase activity is associated with E2F-mediated inhibition of cyclin D1 promoter activity through E2F and Sp1.
Coordinated interactions between cyclin-dependent kinases (Cdks), their target "pocket proteins" (the retinoblastoma protein [pRB], p107, and p130), the pocket protein binding E2F-DP complexes, and the Cdk inhibitors regulate orderly cell cycle progression. The cyclin D1 gene encodes a regulatory subunit of the Cdk holoenzymes, which phosphorylate the tumor suppressor pRB, leading to the release of free E2F-1. Overexpression of E2F-1 can induce apoptosis and may either promote or inhibit cellular proliferation, depending upon the cell type. In these studies overexpression of E2F-1 inhibited cyclin D1-dependent kinase activity, cyclin D1 protein levels, and promoter activity. The DNA binding domain, the pRB pocket binding region, and the amino-terminal Sp1 binding domain of E2F-1 were required for full repression of cyclin D1. Overexpression of pRB activated the cyclin D1 promoter, and a dominant interfering pRB mutant was defective in cyclin D1 promoter activation. Two regions of the cyclin D1 promoter were required for full E2F-1-dependent repression. The region proximal to the transcription initiation site at -127 bound Sp1, Sp3, and Sp4, and the distal region at -143 bound E2F-4-DP-1-p107. In contrast with E2F-1, E2F-4 induced cyclin D1 promoter activity. Differential regulation of the cyclin D1 promoter by E2F-1 and E2F-4 suggests that E2Fs may serve distinguishable functions during cell cycle progression. Inhibition of cyclin D1 abundance by E2F-1 may contribute to an autoregulatory feedback loop to reduce pRB phosphorylation and E2F-1 levels in the cell.
Watanabe
G
G
Albert Einstein Cancer Center, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Albanese
C
C
Lee
R J
RJ
Reutens
A
A
Vairo
G
G
Henglein
B
B
Pestell
R G
RG
D016475:3T3 Cells; D000818:Animals; D002352:Carrier Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D019938:Cyclin D1 / Q000235:genetics* / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050704:E2F4 Transcription Factor; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D011401:Promoter Regions, Genetic; D016160:Retinoblastoma Protein / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014327:Trophoblasts / Q000201:enzymology; D014407:Tumor Cells, Cultured
C533431:Arid4a protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D050704:E2F4 Transcription Factor; C493762:E2F4 protein, human; C493754:E2f1 protein, mouse; C493763:E2f4 protein, mouse; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D016329:Sp1 Transcription Factor; D050680:Transcription Factor DP1; D014157:Transcription Factors; D019938:Cyclin D1; D018844:Cyclin-Dependent Kinases