Introduction to the E2F Family: Protein Structure and Gene Regulation

Slansky, Jill E.; Farnham, P

doi:10.1007/978-3-642-79910-5_1

Cited by 164 publications

(207 citation statements)

References 102 publications

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“…Of these motifs, the E2F sites are most consistent with the type of cell cycle regulation observed. The upstream E2F motif is similar to one found in the human DNA polymerase a gene while the exon 1 sequence ®ts the consensus TTTSSSSS (S=C or G) (Slansky and Farnham, 1996). There are no obvious TATA or CAAT boxes within the minimal promoter region and like many promoters, this one is GC rich (overall 63% in PromD2) and therefore contains several candidate SP1 sites.…”

Section: Sequence Analysis Of Minimal Promotermentioning

confidence: 76%

Isolation and initial characterization of the BRCA2 promoter

et al. 1999

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The hereditary breast cancer susceptibility gene, BRCA2, is considered to be a tumor suppressor gene that may be involved in the cellular response to DNA damage. The transcript for this gene is cell cycle regulated with mRNA levels reaching a peak just before the onset of DNA synthesis. In order to de®ne the mechanisms by which BRCA2 is transcriptionally regulated, we have begun to study upstream regulatory sequences. In this report, we de®ne a minimal promoter region that has strong activity in human breast epithelial cells. Deletions of this sequence narrowed the strong basal activity to a region extending from 766 to +129 with respect to the BRCA2 transcriptional start site. This sequence demonstrated cell cycle regulated activity with kinetics similar to the endogenous transcript. Examination of the sequence revealed several consensus binding sites for transcription factors including an E-box, E2F and Ets recognition motifs. Electrohoretic mobility shift assays revealed speci®c protein binding to two sequences upstream of the start site; the palindromic Ebox and an Ets/E2F site. Site-directed mutagenesis of either of these sites reduced both the basal activity in log phase cells and the cell cycle regulated activity of the promoter. Mutational inactivation of both sites within the same construct eectively eliminated promoter activity. Antibodies to candidate transcription factors used in super shift experiments revealed speci®c interactions between the BRCA2 promoter and the basic region/helix ± loop ± helix containing USF-1 and 2 proteins and Elf-1, an Ets domain protein. Binding of these factors depended upon the presence of intact recognition sequences. The USF factors were shown to bind predominantly as a heterodimeric complex of USF-1 and 2 while Elf-1 bound the promoter when it was not occupied by USF. Co-transfection studies with USF proteins and the varicella zoster IE62 protein provide evidence for the involvement of endogenous and exogenous USF in the activation of the BRCA2 promoter. We propose that interactions between USF-1, USF-2 and Elf-1 play an important role in the transcriptional regulation of the BRCA2 gene.

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Section: Sequence Analysis Of Minimal Promotermentioning

confidence: 76%

Isolation and initial characterization of the BRCA2 promoter

et al. 1999

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“…For instance, mutation of the E2F sites in the DHFR promoter does not elevate activity in quiescent cells but rather eliminates the activation in mid-to late G 1 (74). Moreover, although cyclin D-cdk4 can activate the E2F1 promoter in quiescent cells, consistent with the elimination of repressor activity by phosphorylation of p130 or Rb, cyclin D-cdk4 does not activate the DHFR promoter under these circumstances (35).…”

Section: Discussionmentioning

confidence: 99%

The Accumulation of an E2F-p130 Transcriptional Repressor Distinguishes a G₀ Cell State From a G₁ Cell State

Smith

Leone

DeGregori

et al. 1996

Molecular and Cellular Biology

212

209

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Previous studies have demonstrated cell cycle-dependent specificities in the interactions of E2F proteins with Rb family members. We now show that the formation of an E2F-p130 complex is unique to cells in a quiescent, G 0 state. The E2F-p130 complex does not reform when cells reenter a proliferative state and cycle through G 1 . The presence of an E2F-p130 complex in quiescent cells coincides with the E2F-mediated repression of transcription of the E2F1 gene, and we show that the E2F sites in the E2F1 promoter are important as cells enter quiescence but play no apparent role in cycling cells. In addition, the decay of the E2F-p130 complex as cells reenter the cell cycle requires the action of G 1 cyclin-dependent kinase activity. We conclude that the accumulation of the E2F-p130 complex in quiescent cells provides a negative control of certain key target genes and defines a functional distinction between these G 0 cells and cells that exist transiently in G 1 .The role of the E2F transcription factor in the control of cell proliferation, and as a target for the action of the retinoblastoma tumor suppressor protein (Rb) in arresting cell growth in G 1 , is now well established (27,46,59). Rb activity is regulated by phosphorylation in G 1 (7,9,19,47,49,55,56,62), through the action of the G 1 cyclin-dependent kinases (18,26,31,33,41,81). The growth-regulatory activity of Rb directly coincides with its ability to physically interact with and regulate E2F (1,3,11,28,29,39,63). Indeed, overexpression of the E2F1 product, or production of an E2F1 chimera lacking sequences recognized by Rb, is sufficient to induce S phase in quiescent cell populations (2,16,38,65,67,69). Moreover, deregulated expression of E2F1, in cooperation with an activated ras oncogene, can lead to oncogenic transformation of primary rat embryo cells (36) or an established cell line (73).The Rb gene defines one member of a family of related genes encoding proteins that share the ability to interact with and regulate E2F transcriptional activity and to suppress cell growth. The p107 and p130 proteins have considerable sequence homology with Rb (25,51,54,86,87), and each is regulated by the action of G 1 cyclin-dependent kinases (4, 78). Nevertheless, despite these similarities, it is also true that there are distinct specificities in the interaction of the Rb family of proteins with the E2F family. A number of experiments have now shown that p130 interacts with E2F in quiescent, G 0 cells and early G 1 cells that have been stimulated to proliferate whereas the p107 protein forms an E2F complex as cells enter and progress through S phase (13,17,71). The Rb interaction can be seen throughout the cell cycle although there is an increase in the complex as cells move through mid-to late G 1 that likely reflects the increased amount of E2F at this time (34). Specificities can also be seen in the nature of the proteins involved in the various interactions. The p130 and p107 proteins have been shown to bind to a specific subset of the E2F family proteins...

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“…The transcriptionally active forms of E2F appear to be heterodimers, with one subunit encoded by the E2F-like gene family and one subunit encoded by the DP-like gene family (reviewed by Slansky and Farnham, 1996). To date, seven molecules which contribute to E2F activity have been isolated from mammalian cells.…”

Section: Introductionmentioning

confidence: 99%

Transcriptional squelching by ectopic expression of E2F-1 and p53 is alleviated by proteasome inhibitors MG-132 and lactacystin

Magae

Illenye

et al. 1997

Oncogene

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The transcription factors p53 and E2F-1 play important roles in the control of cell cycle progression. In transient transfection experiments, expression of E2F-1, other E2F family members, or p53 squelched transcription from cotransfected plasmids in a dose-dependent manner. Although the proteasome inhibitors MG-132 and lactacystin markedly increased the level of expression of E2F-1 and p53, these inhibitors completely alleviated squelching by both proteins. Several observations indicate MG-132 alleviates squelching by in¯uencing the conformation of newly synthesized p53 and E2F-1: MG-132 increased the fraction of wild type p53 bound by a monoclonal antibody which preferentially recognizes mutant conformers of p53, increased binding of hsp70 to p53 and inhibited nuclear accumulation of both p53 and E2F-1, but not the pocket protein p107. The protease inhibitors ALLN and ALLM did not in¯uence expression of E2F-1 or p53, nor did they alleviate squelching by either transcription factor. Because MG-132 and lactacycstin are highly speci®c inhibitors of the proteasome protease, our results suggest that the proteasome in¯uences post-translational processes involved in proper folding and cytoplasmic clearing of E2F-1 and p53.

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Introduction to the E2F Family: Protein Structure and Gene Regulation

Cited by 164 publications

References 102 publications

Isolation and initial characterization of the BRCA2 promoter

Isolation and initial characterization of the BRCA2 promoter

The Accumulation of an E2F-p130 Transcriptional Repressor Distinguishes a G₀ Cell State From a G₁ Cell State

Transcriptional squelching by ectopic expression of E2F-1 and p53 is alleviated by proteasome inhibitors MG-132 and lactacystin

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Introduction to the E2F Family: Protein Structure and Gene Regulation

Cited by 164 publications

References 102 publications

Isolation and initial characterization of the BRCA2 promoter

Isolation and initial characterization of the BRCA2 promoter

The Accumulation of an E2F-p130 Transcriptional Repressor Distinguishes a G0 Cell State From a G1 Cell State

Transcriptional squelching by ectopic expression of E2F-1 and p53 is alleviated by proteasome inhibitors MG-132 and lactacystin

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The Accumulation of an E2F-p130 Transcriptional Repressor Distinguishes a G₀ Cell State From a G₁ Cell State