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Yousef AF, Brandl CJ, Mymryk JS. Requirements for E1A dependent transcription in the yeast Saccharomyces cerevisiae. BMC Mol Biol 2009; 10:32. [PMID: 19374760 PMCID: PMC2674444 DOI: 10.1186/1471-2199-10-32] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 04/17/2009] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND The human adenovirus type 5 early region 1A (E1A) gene encodes proteins that are potent regulators of transcription. E1A does not bind DNA directly, but is recruited to target promoters by the interaction with sequence specific DNA binding proteins. In mammalian systems, E1A has been shown to contain two regions that can independently induce transcription when fused to a heterologous DNA binding domain. When expressed in Saccharomyces cerevisiae, each of these regions of E1A also acts as a strong transcriptional activator. This allows yeast to be used as a model system to study mechanisms by which E1A stimulates transcription. RESULTS Using 81 mutant yeast strains, we have evaluated the effect of deleting components of the ADA, COMPASS, CSR, INO80, ISW1, NuA3, NuA4, Mediator, PAF, RSC, SAGA, SAS, SLIK, SWI/SNF and SWR1 transcriptional regulatory complexes on E1A dependent transcription. In addition, we examined the role of histone H2B ubiquitylation by Rad6/Bre1 on transcriptional activation. CONCLUSION Our analysis indicates that the two activation domains of E1A function via distinct mechanisms, identify new factors regulating E1A dependent transcription and suggest that yeast can serve as a valid model system for at least some aspects of E1A function.
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Affiliation(s)
- Ahmed F Yousef
- Department of Microbiology & Immunology, University of Western Ontario, London, Ontario, Canada.
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2
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Pelka P, Ablack JNG, Torchia J, Turnell AS, Grand RJA, Mymryk JS. Transcriptional control by adenovirus E1A conserved region 3 via p300/CBP. Nucleic Acids Res 2009; 37:1095-106. [PMID: 19129215 PMCID: PMC2651774 DOI: 10.1093/nar/gkn1057] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The human adenovirus type 5 (HAdV-5) E1A 13S oncoprotein is a potent regulator of gene expression and is used extensively as a model for transcriptional activation. It possesses two independent transcriptional activation domains located in the N-terminus/conserved region (CR) 1 and CR3. The protein acetyltransferase p300 was previously identified by its association with the N-terminus/CR1 portion of E1A and this association is required for oncogenic transformation by E1A. We report here that transcriptional activation by 13S E1A is inhibited by co-expression of sub-stoichiometric amounts of the smaller 12S E1A isoform, which lacks CR3. Transcriptional inhibition by E1A 12S maps to the N-terminus and correlates with the ability to bind p300/CBP, suggesting that E1A 12S is sequestering this limiting factor from 13S E1A. This is supported by the observation that the repressive effect of E1A 12S is reversed by expression of exogenous p300 or CBP, but not by a CBP mutant lacking actyltransferase activity. Furthermore, we show that transcriptional activation by 13S E1A is greatly reduced by siRNA knockdown of p300 and that CR3 binds p300 independently of the well-characterized N-terminal/CR1-binding site. Importantly, CR3 is also required to recruit p300 to the adenovirus E4 promoter during infection. These results identify a new functionally significant interaction between E1A CR3 and the p300/CBP acetyltransferases, expanding our understanding of the mechanism by which this potent transcriptional activator functions.
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Affiliation(s)
- Peter Pelka
- Department of Oncology, The University of Western Ontario, London Regional Cancer Centre, London, Ontario, Canada.
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3
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Boyd JM, Loewenstein PM, Tang Qq QQ, Yu L, Green M. Adenovirus E1A N-terminal amino acid sequence requirements for repression of transcription in vitro and in vivo correlate with those required for E1A interference with TBP-TATA complex formation. J Virol 2002; 76:1461-74. [PMID: 11773419 PMCID: PMC135854 DOI: 10.1128/jvi.76.3.1461-1474.2002] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2001] [Accepted: 10/17/2001] [Indexed: 11/20/2022] Open
Abstract
The adenovirus (Ad) E1A 243R oncoprotein encodes an N-terminal transcription repression domain that is essential for early viral functions, cell immortalization, and cell transformation. The transcription repression function requires sequences within amino acids 1 to 30 and 48 to 60. To elucidate the roles of the TATA-binding protein (TBP), p300, and the CREB-binding protein (CBP) in the mechanism(s) of E1A repression, we have constructed 29 amino acid substitution mutants and 5 deletion mutants spanning the first 30 amino acids within the E1A 1-80 polypeptide backbone. These mutant E1A polypeptides were characterized with regard to six parameters: the ability to repress transcription in vitro and in vivo, to disrupt TBP-TATA box interaction, and to bind TBP, p300, and CBP. Two regions within E1A residues 1 to 30, amino acids 2 to 6 and amino acid 20, are critical for E1A transcription repression in vitro and in vivo and for the ability to interfere with TBP-TATA interaction. Replacement of 6Cys with Ala in the first region yields the most defective mutant. Replacement of 20Leu with Ala, but not substitutions in flanking residues, yields a substantially defective phenotype. Protein binding assays demonstrate that replacement of 6Cys with Ala yields a mutant completely defective in interaction with TBP, p300, and CBP. Our findings are consistent with a model in which the E1A repression function involves interaction of E1A with p300/CBP and interference with the formation of a TBP-TATA box complex.
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Affiliation(s)
- Janice M Boyd
- Institute for Molecular Virology, Saint Louis University School of Medicine, St. Louis, Missouri 63110, USA
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4
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Whalen SG, Marcellus RC, Whalen A, Ahn NG, Ricciardi RP, Branton PE. Phosphorylation within the transactivation domain of adenovirus E1A protein by mitogen-activated protein kinase regulates expression of early region 4. J Virol 1997; 71:3545-53. [PMID: 9094626 PMCID: PMC191501 DOI: 10.1128/jvi.71.5.3545-3553.1997] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A critical role of the 289-residue (289R) E1A protein of human adenovirus type 5 during productive infection is to transactivate expression of all early viral transcription. Sequences within and proximal to conserved region 3 (CR3) promote expression of these viral genes through interactions with a variety of transcription factors requiring the zinc binding motif in CR3 and in some cases a region at the carboxy-terminal end of CR3, including residues 183 to 188. It is known that 3',5' cyclic AMP (cAMP) reduces the level of phosphorylation of the 289R E1A protein through the activation of protein phosphatase 2A by the E4orf4 protein. This study was designed to identify the E1A phosphorylation sites affected by E4orf4 expression and to determine their importance in regulation of E1A activity. We report here that two previously unidentified sites at Ser-185 and Ser-188 are the targets for decreased phosphorylation in response to cAMP. At least one of these sites, presumably Ser-185, is phosphorylated in vitro by purified mitogen-activated protein kinase (MAPK), and both are hyperphosphorylated in cells which express a constitutively active form of MAPK kinase. Analysis of E1A-mediated transactivation activity indicated that elevated phosphorylation at these sites increased expression of the E4 promoter but not that of E3. We have recently shown that one or more E4 products induce cell death due to p53-independent apoptosis, and thus it seems likely that one role of the E4orf4 protein is to limit production of toxic E4 products by limiting expression of the E4 promoter.
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Affiliation(s)
- S G Whalen
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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5
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Song CZ, Loewenstein PM, Toth K, Tang Q, Nishikawa A, Green M. The adenovirus E1A repression domain disrupts the interaction between the TATA binding protein and the TATA box in a manner reversible by TFIIB. Mol Cell Biol 1997; 17:2186-93. [PMID: 9121468 PMCID: PMC232067 DOI: 10.1128/mcb.17.4.2186] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The human adenovirus E1A 243 amino acid oncoprotein possesses a transcription repression function that appears to be linked with its ability to induce cell cycle progression and to inhibit cell differentiation. The molecular mechanism of E1A repression has been poorly understood. Recently, we reported that the TATA binding protein (TBP) is a cellular target of E1A repression. Here we demonstrate that the interaction between TBP and the E1A repression domain is direct and specific. The TBP binding domain within E1A 243R maps to E1A N-terminal residues approximately 1 to 35 and is distinct from the TBP binding domain within conserved region 3 unique to the E1A 289R transactivator. An E1A protein fragment consisting of only the E1A N-terminal 80 amino acids (E1A 1-80) and containing the E1A repression function was found to block the interaction between TBP and the TATA box element as shown by gel mobility and DNase protection analysis. Interestingly, a preformed TBP-TATA box promoter complex can be dissociated by E1A 1-80. Further, TFIIB can prevent E1A disruption of TBP-TATA box interaction. TFIIB, like TBP, can overcome E1A repression of transcription in vitro. The ability of the E1A repression domain to block TBP interaction with the TATA box and the ability of TFIIB to reverse E1A disruption of the TBP-TATA box complex implies a mechanism for E1A repression distinct from those of known cellular repressors that target TBP.
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Affiliation(s)
- C Z Song
- Institute for Molecular Virology, Saint Louis University School of Medicine, Missouri 63110, USA
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6
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Geisberg JV, Lee WS, Berk AJ, Ricciardi RP. The zinc finger region of the adenovirus E1A transactivating domain complexes with the TATA box binding protein. Proc Natl Acad Sci U S A 1994; 91:2488-92. [PMID: 8146144 PMCID: PMC43394 DOI: 10.1073/pnas.91.7.2488] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The 289R E1A protein of adenovirus transactivates a variety of viral and cellular promoters through protein-protein interactions. In earlier studies, mutational analyses of the E1A transactivating domain identified residues that are critical for transactivation and implied that the zinc finger region of the transactivating domain binds a transcription factor. Also, the E1A activation domain was found to bind to the TATA box binding protein (TBP) in vitro. Here, we tested the significance of the E1A-TBP interaction for E1A transactivation by analyzing the effects of conservative substitutions at each of the 49 residues of the E1A activation domain. Seven of the substitutions significantly diminished TBP binding in vitro. All of these were in the zinc finger region and were defective for transactivation in vivo. The perfect correlation between reduced TBP binding and transactivation argues strongly that a direct interaction between the E1A activation domain and TBP is critical to the mechanism of E1A activation. This genetic analysis leads us to further suggest that another factor, which is limiting, is also necessary for E1A-mediated transactivation.
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Affiliation(s)
- J V Geisberg
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia 19104
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7
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Webster LC, Zhang K, Chance B, Ayene I, Culp JS, Huang WJ, Wu FY, Ricciardi RP. Conversion of the E1A Cys4 zinc finger to a nonfunctional His2,Cys2 zinc finger by a single point mutation. Proc Natl Acad Sci U S A 1991; 88:9989-93. [PMID: 1835093 PMCID: PMC52852 DOI: 10.1073/pnas.88.22.9989] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Trans-activation by the adenovirus E1A 289R protein requires a zinc finger defined by Cys-154, Cys-157, Cys-171, and Cys-174. Whereas individually replacing the four cysteine residues with serines resulted in a loss of transactivation, only three of the Cys----Ser mutants (C157S, C171S, and C174S) lost the ability to bind Zn(II). X-ray absorption fine structure analysis revealed that, in the wild-type protein, Zn(II) is coordinated by four cysteine residues whereas in the C154S mutant, Zn(II) is coordinated by two histidines and two cysteines. The mutant protein probably retains, as ligands, two cysteines on the right side of the zinc finger (Cys-171 and Cys-174) and recruits two of the four histidines on the left side (His-149, His-152, His-158, and His-160), despite the presence of Cys-157. This finding may shed light on the general structural requirements of zinc fingers.
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Affiliation(s)
- L C Webster
- Institute for Structural Functional Studies, Philadelphia, PA 19104
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8
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trans-dominant mutants of E1A provide genetic evidence that the zinc finger of the trans-activating domain binds a transcription factor. Mol Cell Biol 1991. [PMID: 1831535 DOI: 10.1128/mcb.11.9.4287] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 289R E1A protein of adenovirus stimulates transcription of early viral and certain cellular genes. trans-Activation requires residues 140 to 188, which encompass a zinc finger. Several studies have indicated that trans-activation by E1A is mediated through cellular transcription factors. In particular, the ability of the trans-dominant E1A point mutant hr5 (Ser-185 to Asn) to inhibit wild-type E1A trans-activation was proposed to result from the sequestration of a cellular factor. Using site-directed mutagenesis, we individually replaced every residue within and flanking the trans-activating domain with a conservative amino acid, revealing 16 critical residues. Six of the individual substitutions lying in a contiguous stretch C terminal to the zinc finger (carboxyl region183-188) imparted a trans-dominant phenotype. trans-Dominance was even produced by deletion of the entire carboxyl region183-188. Conversely, an intact finger region147-177 was absolutely required for trans-dominance, since second-site substitution of every critical residue in this region abrogated the trans-dominant phenotype of the hr5 protein. These data indicate that the finger region147-177 bind a limiting cellular transcription factor and that the carboxyl region183-188 provides a separate and essential function. In addition, we show that four negatively charged residues within the trans-activating domain do not comprise a distinct acidic activating region. We present a model in which the trans-activating domain of E1A binds to two different cellular protein targets through the finger and carboxyl regions.
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9
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Webster LC, Ricciardi RP. trans-dominant mutants of E1A provide genetic evidence that the zinc finger of the trans-activating domain binds a transcription factor. Mol Cell Biol 1991; 11:4287-96. [PMID: 1831535 PMCID: PMC361289 DOI: 10.1128/mcb.11.9.4287-4296.1991] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The 289R E1A protein of adenovirus stimulates transcription of early viral and certain cellular genes. trans-Activation requires residues 140 to 188, which encompass a zinc finger. Several studies have indicated that trans-activation by E1A is mediated through cellular transcription factors. In particular, the ability of the trans-dominant E1A point mutant hr5 (Ser-185 to Asn) to inhibit wild-type E1A trans-activation was proposed to result from the sequestration of a cellular factor. Using site-directed mutagenesis, we individually replaced every residue within and flanking the trans-activating domain with a conservative amino acid, revealing 16 critical residues. Six of the individual substitutions lying in a contiguous stretch C terminal to the zinc finger (carboxyl region183-188) imparted a trans-dominant phenotype. trans-Dominance was even produced by deletion of the entire carboxyl region183-188. Conversely, an intact finger region147-177 was absolutely required for trans-dominance, since second-site substitution of every critical residue in this region abrogated the trans-dominant phenotype of the hr5 protein. These data indicate that the finger region147-177 bind a limiting cellular transcription factor and that the carboxyl region183-188 provides a separate and essential function. In addition, we show that four negatively charged residues within the trans-activating domain do not comprise a distinct acidic activating region. We present a model in which the trans-activating domain of E1A binds to two different cellular protein targets through the finger and carboxyl regions.
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Affiliation(s)
- L C Webster
- Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104
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10
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Gitlin SD, Lindholm PF, Marriott SJ, Brady JN. Transdominant human T-cell lymphotropic virus type I TAX1 mutant that fails to localize to the nucleus. J Virol 1991; 65:2612-21. [PMID: 2016773 PMCID: PMC240619 DOI: 10.1128/jvi.65.5.2612-2621.1991] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Human T-cell lymphotropic virus type I (HTLV-I) encodes a 40-kDa nuclear transactivating phosphoprotein, TAX1. The results presented in this study demonstrate that deletion of amino acids 2 through 59 of TAX1 (delta 58 TAX1) decreased transactivation of the HTLV-I long terminal repeat 10- to 20-fold. S1 nuclease analysis revealed that the decrease in transactivation of the HTLV-I long terminal repeat was associated with a lack of RNA synthesis. In contrast to the nuclear localization of the wild-type TAX1 protein, indirect immunofluorescence analysis demonstrated that delta 58 TAX1 failed to localize to the nucleus, indicating that the TAX1 nuclear localization sequence is present in amino acids 2 through 59. Cotransfection of wild-type and mutant TAX1 DNAs resulted in the cytoplasmic accumulation of TAX1 and a 25-fold decrease in transactivation. Although several possibilities which may account for this transdominant effect exist, we favor a model in which delta 58 TAX1 interferes with the nuclear localization of wild-type TAX1 protein, perhaps by forming heterodimer complexes.
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Affiliation(s)
- S D Gitlin
- Laboratory of Molecular Virology, National Cancer Institute, Bethesda, Maryland 20892
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11
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Pearson L, Garcia J, Wu F, Modesti N, Nelson J, Gaynor R. A transdominant tat mutant that inhibits tat-induced gene expression from the human immunodeficiency virus long terminal repeat. Proc Natl Acad Sci U S A 1990; 87:5079-83. [PMID: 2195547 PMCID: PMC54265 DOI: 10.1073/pnas.87.13.5079] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Regulation of human immunodeficiency virus (HIV) gene expression is dependent on specific regulatory regions in the long terminal repeat. These regions include the enhancer, SP1, "TATA," and trans-activating (TAR) regions. In addition, viral regulatory proteins such as tat and rev are important in regulating HIV gene expression. The mechanism of tat activation remains the subject of investigation, but effects at both transcriptional and posttranscriptional levels seem likely. Previous mutagenesis of the tat protein revealed that the amino terminus, the cysteine-rich domain, and the basic domain were all required for complete tat activation. Mutants of other viral trans-acting regulatory proteins, including E1A, tax, and VM65, have been identified that were capable of antagonizing the activity of their corresponding wild-type proteins. We wished to determine whether mutants of the tat protein could be identified that exhibited a similar phenotype. One mutant (delta tat) that truncated the basic domain of tat resulted in a transdominant phenotype inhibiting tat-induced gene expression of the HIV long terminal repeat but not other viral promoters. This mutant exhibited its maximal phenotype in cotransfection experiments when present in an 8- to 30-fold molar excess over the wild-type tat gene. Trans-activation of the HIV long terminal repeat by delta tat was very defective at the DNA concentrations used in these experiments. RNase protection analysis indicated that this mutant decreased tat-induced steady-state mRNA levels of the HIV long terminal repeat. Second-site mutations of the delta tat gene in either the amino terminus or cysteine region eliminated the transdominant phenotype. In contrast to tat, which was localized predominantly to the nucleolus, delta tat was present in both the nucleus and cytoplasm, suggesting that it may inhibit tat function by preventing nucleolar localization. Transdominant mutants of tat may have a role in potentially inhibiting HIV gene expression.
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Affiliation(s)
- L Pearson
- Department of Medicine, University of California-Los Angeles School of Medicine 90024
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12
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Ventura AM, Arens MQ, Srinivasan A, Chinnadurai G. Silencing of human immunodeficiency virus long terminal repeat expression by an adenovirus E1a mutant. Proc Natl Acad Sci U S A 1990; 87:1310-4. [PMID: 2137611 PMCID: PMC53464 DOI: 10.1073/pnas.87.4.1310] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Gene expression from the human immunodeficiency virus (HIV) long terminal repeat (LTR) is strongly stimulated by the viral tat gene. The HIV LTR is also activated by several physical and chemical agents and heterologous viral genes, including adenovirus E1a. As E1a has separable transcriptional activation and repression functions, we examined the negative regulatory effects of E1a on the expression of the HIV LTR by using a trans-dominant E1a mutant. Mutant hr5 strongly suppressed the basal activity of the LTR as well as trans-activation of the LTR by heterologous agents such as the cytomegalovirus immediate early gene or DNA-damaging agents such as mitomycin C and UV irradiation. In addition, hr5 also caused significant suppression of tat gene-mediated trans-activation. The suppression of HIV LTR expression by hr5 appears to be mediated, at least in part, by the repression of the HIV enhancer, as the activity of an enhancer test system composed of the human T-cell leukemia virus I LTR containing an HIV-1 enhancer substitution was severely repressed by hr5. Cotransfection of HIV-1 proviral DNA with hr5 DNA resulted in a significant reduction of HIV production.
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Affiliation(s)
- A M Ventura
- Institute for Molecular Virology, Saint Louis University School of Medicine, MO 63110
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13
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Fusion of adenovirus E1A to the glucocorticoid receptor by high-resolution deletion cloning creates a hormonally inducible viral transactivator. Mol Cell Biol 1989. [PMID: 2550806 DOI: 10.1128/mcb.9.9.3878] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 289-amino-acid E1A protein of adenovirus type 2 stimulates transcription from early viral and certain cellular promoters. Its mechanism is not known, and there exist no temperature-sensitive mutants of E1A that could help to elucidate the details of E1A transcriptional activation. To create for E1A such a conditional phenotype, we fused portions of E1A to the human glucocorticoid receptor (GR) to make transactivation by E1A dependent on the presence of dexamethasone. Nested subsets of the E1A coding region, centered around the 46-amino-acid transactivating domain, were substituted for the DNA-binding domain of the GR. One of the resulting chimeric proteins (GR/E1A-99), which included the entire E1A transactivating domain, stimulated expression from a viral early promoter (E3) exclusively in the presence of hormone. GR/E1A-99 did not transactivate a GR-responsive promoter. It therefore exhibited the promoter specificity of E1A while possessing the hormone inducibility of the GR. Two smaller chimeras that contained only portions of the E1A transactivating domain failed to transactivate E3. These three chimeras were constructed by a novel strategy, high-resolution deletion cloning. In this procedure, series of unidirectional deletions were made with exonuclease III on each side of the E1A coding region at a resolution of 1 to 2 nucleotides. The large number of in-frame fragments present in the collection of deleted clones facilitated the construction of the GR/E1A chimeras and can be used to create many additional fusions.
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14
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Becker DM, Hollenberg SM, Ricciardi RP. Fusion of adenovirus E1A to the glucocorticoid receptor by high-resolution deletion cloning creates a hormonally inducible viral transactivator. Mol Cell Biol 1989; 9:3878-87. [PMID: 2550806 PMCID: PMC362449 DOI: 10.1128/mcb.9.9.3878-3887.1989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The 289-amino-acid E1A protein of adenovirus type 2 stimulates transcription from early viral and certain cellular promoters. Its mechanism is not known, and there exist no temperature-sensitive mutants of E1A that could help to elucidate the details of E1A transcriptional activation. To create for E1A such a conditional phenotype, we fused portions of E1A to the human glucocorticoid receptor (GR) to make transactivation by E1A dependent on the presence of dexamethasone. Nested subsets of the E1A coding region, centered around the 46-amino-acid transactivating domain, were substituted for the DNA-binding domain of the GR. One of the resulting chimeric proteins (GR/E1A-99), which included the entire E1A transactivating domain, stimulated expression from a viral early promoter (E3) exclusively in the presence of hormone. GR/E1A-99 did not transactivate a GR-responsive promoter. It therefore exhibited the promoter specificity of E1A while possessing the hormone inducibility of the GR. Two smaller chimeras that contained only portions of the E1A transactivating domain failed to transactivate E3. These three chimeras were constructed by a novel strategy, high-resolution deletion cloning. In this procedure, series of unidirectional deletions were made with exonuclease III on each side of the E1A coding region at a resolution of 1 to 2 nucleotides. The large number of in-frame fragments present in the collection of deleted clones facilitated the construction of the GR/E1A chimeras and can be used to create many additional fusions.
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Affiliation(s)
- D M Becker
- Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104-4268
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15
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The 289-amino acid E1A protein of adenovirus binds zinc in a region that is important for trans-activation. Proc Natl Acad Sci U S A 1988; 85:6450-4. [PMID: 2970640 PMCID: PMC281990 DOI: 10.1073/pnas.85.17.6450] [Citation(s) in RCA: 97] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The E1A gene of adenovirus type 5 encodes two major proteins of 289 and 243 amino acid residues, which are identical except that the larger protein has an internal stretch of 46 amino acids required for efficient trans-activation of early viral promoters. This domain contains a consensus zinc finger motif (Cys-Xaa2-Cys-Xaa13-Cys-Xaa2-Cys) in which the cysteine residues serve as postulated ligands. Atomic absorption spectrophotometry applied to bacterially expressed E1A proteins revealed that the 289-amino acid protein binds one zinc ion, whereas the 243-amino acid protein binds no zinc. Replacing individual cysteine residues of the finger with other amino acids destroyed the trans-activating ability of the 289-amino acid protein, even when structurally or functionally conserved amino acids were substituted. These results strongly suggest that the zinc finger of the 46-amino acid domain is intimately linked to the ability of the large E1A protein to stimulate transcription of E1A-inducible promoters. Furthermore, zinc binding to one of the mutant finger proteins suggests either that only a precise finger structure formed by the tetrahedral coordination of zinc to the four consensus ligands is required for trans-activation or, possibly, that one of several neighboring histidine residues in various combinations with three of the consensus cysteine residues normally coordinates zinc. How the zinc finger in E1A might interact with DNA or protein to bring about trans-activation is discussed.
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16
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Garcia J, Wu F, Gaynor R. Upstream regulatory regions required to stabilize binding to the TATA sequence in an adenovirus early promoter. Nucleic Acids Res 1987; 15:8367-85. [PMID: 2959908 PMCID: PMC306365 DOI: 10.1093/nar/15.20.8367] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Of the five early adenovirus promoters, the early region 3 (E3) promoter is one of the most strongly induced by the E1A protein. To identify cellular proteins involved in both the basal and E1A-induced transcriptional regulation of the E3 promoter, DNase I footprinting using partially purified Hela cell extracts was performed. Four regions of the E3 promoter serve as binding domains for cellular proteins. These regions are found between -156 to -179 (site IV), -83 to -103 (site III), -47 to -67 (site II), and -16 to -37 (site I), relative to the start of transcription. Examination of the DNA sequences in each binding domain suggests that site III likely serves as a binding site for activator protein 1 (AP-1), site II for the cyclic AMP regulatory element binding protein (CREB), and site I for a TATA binding factor. The factors binding to either site II or III were sufficient to stabilize binding to the TATA sequence (site I). Mutagenesis studies indicated that both sites II and III, in addition to site I, are needed for complete basal and E1A-induced transcription. These results suggest that multiple cellular factors are involved in both the basal and E1A-induced transcriptional regulation of the E3 promoter, and that either of two upstream regions are capable of stabilizing factor binding to the TATA sequence.
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Affiliation(s)
- J Garcia
- Department of Medicine, School of Medicine, Jonnson Comprehensive Cancer Center, Los Angeles, CA 90024
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