Concentration dependence of transcriptional transactivation in inducible E1A-containing human cells.

Brunet, L J; Berk, A J

doi:10.1128/mcb.8.11.4799

Cited by 32 publications

(19 citation statements)

References 30 publications

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“…RESULTS AND DISCUSSION In a previous report (8), the construction of ElA-expressing HT1080 fibrosarcoma and A2058 melanoma cell lines was described; ElA-expressing HeLa cells (9) (8,9) and, in the present study, protein expression was documented by immunoprecipitation with ElA-specific monoclonal antibodies (Fig. 1).…”

supporting

confidence: 53%

Antioncogenic effect of adenovirus E1A in human tumor cells.

Frisch

1991

Proc. Natl. Acad. Sci. U.S.A.

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Stable expression of the adenovirus 5 ElA gene reduced anchorage-independent growth and tumorigenfc potential, caused cytoskeletal reorganization, nduced flat morphology, and restored contact inhibition in three human-tumor cell lines. By these criteria, EMA appears to be functonally indistinguishable from a tumor suppressor gene in this context. The apparent paradox accorded by the observations of the ability of ElA to transform rodent cells in cooperation with other oncogenes suggests that ElA may be the prototype of a class of growth-regulatory proteins having co-text-specffic transorming and antioncogenic activities.

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supporting

confidence: 53%

Antioncogenic effect of adenovirus E1A in human tumor cells.

Frisch

1991

Proc. Natl. Acad. Sci. U.S.A.

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“…- (5,26) and thereby stimulate only promoters that contain that sequence, Ela does not function through any one sequence, does not specifically bind to DNA, and therefore is not limited in the promoters that it stimulates (1,8,18). Rather, Ela promiscuously stimulates transcription: it increases expression from a broad variety of promoters in transfection experiments and stimulates a smaller but still substantial number of viral and cellular promoters during the natural course of infection (1,6,11,16,31,33,39,40,42).…”

Section: Resultsmentioning

confidence: 99%

E1a transactivation of human HSP70 gene promoter substitution mutants is independent of the composition of upstream and TATA elements.

Taylor

Kingston

1990

Mol. Cell. Biol.

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We have analyzed 41 deletion, linker scan, and substitution mutants of the human HSP7O gene promoter for activation by the adenovirus Ela region. No natural element of the HSP70 gene promoter was required for activation. To investigate specific interactions between Ela and transcription factors, a set of 24 promoters containing all possible combinations of eight different upstream or TATA motifs was investigated for Ela stimulation. Ela transactivated the promoter regardless of the particular TATA motif present. Furthermore, there was no dramatic correlation between any upstream motif and activation by Ela. These data suggest that Ela does not stimulate transcription via an interaction with any specific transcription factor but instead suggest that Ela interacts via the general transcription machinery.The adenovirus Ela proteins are potent activators of transcription, stimulating expression from both viral and cellular promoters (3,15). Despite extensive experimentation, the mechanism of Ela transactivation remains poorly understood. Ela has shown no sequence-specific DNAbinding activity (8), and detailed promoter mutagenesis has not identified an element important for induction by Ela that is not also required for full basal levels of transcription (11,30,42; reviewed in references 2 and 18). Therefore, attention has turned to the host-cell DNA-binding transcription factors for potential targets. For example, studies focused on viral promoters have suggested that Ela increases the transcriptional activity of the cellular factors E2F and E4F by increasing their DNA-binding activities (19,32). Others have proposed that the factor which binds the TATA element (e.g., transcription factor TFIID) is the target that mediates induction by Ela (22,35,51).Ela may not modify a specific factor. It has been proposed that Ela possesses both promoter-directing and transcriptional activation domains analogous to those of cellular transcriptional activators (23). In this model, Ela utilizes its promoter-directing domain to recognize and bind to a DNAbound protein on the promoter, after which the activation domain functions to stimulate transcription. It was proposed that a limited number of DNA-bound factors may be recognized by Ela to mediate transcriptional activation; for example, activation transcription factor (ATF), a factor common to many Ela-induced promoters, might be one target (7,14,20,21,25). An explicit prediction of this model is that Ela physically interacts with a domain present on the promoter complex. If this domain is formed by one or more specific DNA-bound factors, one would predict that certain factors or combinations of factors would produce an inducible promoter, whereas other combinations would produce a promoter refractory to stimulation. The numerous reports of specific factors being necessary for full induction of a promoter may reflect the ability of those factors to create a domain that interacts effectively with Ela. * Corresponding author.Alternatively, Ela might not recognize any specific domain...

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“…The extent of induction was greater in Ad5 infections, presumably because of the difference in efficiency between the two techniques. The cotransfection technique was preferred because it avoids the complicating effects of viral infection on host cell RNA metabolism (5).…”

Section: Discussionmentioning

confidence: 99%

E1a transactivation of the human HSP70 promoter is mediated through the basal transcriptional complex.

Williams¹,

McClanahan²,

Morimoto³

1989

Mol. Cell. Biol.

154

114

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We have examined the promoter sequence requirements for Ela transactivation of the human HSP70 gene by using a transient cotransfection assay. A 5' deletion study has defined a basal transcription unit extending to -74 relative to the transcription initiation site which was fully Ela responsive. Further deletion, abolishing a CCAAT element at -67, drastically reduced basal and Ela-induced expression. A linker-scanner analysis has identified four functional elements within the basal transcription unit which may interact with CTF, SPI, TFIID, and an ATF/APl-like factor. Sequences between -100 and -188 can partially compensate for mutations in these elements. No mutation specifically abolished Ela inducibility. Any reduction in absolute Ela-induced levels was accompanied by a corresponding reduction in absolute basal levels, thereby maintaining a constant relative fold induction. We conclude that Ela transactivation of the human HSP70 promoter does not require any single basal transcription element. We also examined an HSP70 promoter fragment, containing the CCAAT element at -67 and the purine-rich element at -54, out of its normal context by fusing it upstream of a transcriptionally inactive herpes simplex virus thymidine kinase deletion construct containing only the TATA box. The resulting chimeric promoter was fully Ela responsive. Mutagenesis of this promoter fusion demonstrated that the CCAAT element was essential for detectable basal and Ela-induced expression.Mutations in the purine-rich element resulted in an rendered the promoter nonresponsive to Ela.An important point at which gene expression is controlled is transcriptional initiation. The regulation of this step is mediated by DNA binding tr-ans-acting factors that select the site and modulate the rate of specific initiation (for reviews, see references 20 and 41). General transcription factors, such as TFIID, direct RNA polymerase II to the specific start site. The same types of general factors are probably required for specific initiation from most protein-coding genes. Promoter-specific factors bind to transcription elements that regulate the frequency of RNA chain initiation. One class of transcription elements, called upstream elements, is characterized by short sequences of approximately 10 base pairs (bp) that are usually located up to about 110 bp upstream from the RNA start site. These elements modulate transcription in a distance-dependent manner. The other class of transcription elements is enhancers, which are capable of modulating transcription independent of both orientation and distance. Regulation of promoter activity depends on both the number and the type of transcription elements present. The combinatorial organization of elements allows for many complex regulatory patterns with only a small number of transcription factors.Superimposed on the regulation conferred by protein-DNA interactions are the effects of transcription factors which do not bind to DNA. A well-studied example is the 289-amino-acid adenovirus Ela protein, which has ...

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Concentration dependence of transcriptional transactivation in inducible E1A-containing human cells.

Cited by 32 publications

References 30 publications

Antioncogenic effect of adenovirus E1A in human tumor cells.

Antioncogenic effect of adenovirus E1A in human tumor cells.

E1a transactivation of human HSP70 gene promoter substitution mutants is independent of the composition of upstream and TATA elements.

E1a transactivation of the human HSP70 promoter is mediated through the basal transcriptional complex.

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