A cellular protein, activating transcription factor, activates transcription of multiple E1A-inducible adenovirus early promoters.

Abstract

We have examined the relationship between sequence-specific DNA-binding proteins that activate transcription of ElA-inducible adenovirus early promoters. Factors previously referred to as E4F1 and E2A-EF bind to the E4 and E2A promoters, respectively. We demonstrate here that E4F1 and E2A-EF have identical DNA-binding specificity. Moreover, E4F1 and E2A-EF both activate transcription of the E4 and E2A promoters in vitro. These findings demonstrate that E4F1 and E2A-EF are the same factor, which we have designated activating transcription factor, or ATF. In addition to the E4 and E2A promoters, ATF binds to an important functional element of the ElA-inducible E3 promoter. Interaction of a common activator protein, ATF, with multiple ElA-inducible early viral promoters, suggests a significant role for ATF in ElA-mediated transcriptional activation.The EIA gene of adenovirus produces closely related 13S and 12S mRNAs that encode nuclear-localized phosphoproteins with diverse transcriptional regulatory properties (1-3). The EMA 13S gene product coordinately activates a set of viral early genes (EIA, EIB, E2A, E3, and E4) during a productive infection of permissive human cells (4-7). The ElA 12S gene product encodes a transcriptional repression function that appears to act through transcriptional enhancer elements (8-10). In addition to regulating viral transcription, ElA activates or represses transcription of a limited number of cellular genes (11,12), and activates polymerase III-dependent promoters (for review, see ref. E4 and E3 transcription (18, 19). For the EIB promoter (22) and the cellular /-globin promoter (23), the "TATA" box has been implicated as an ElA-responsive promoter element. Thus activation of a variety of ElA-inducible promoters appears to involve different cellular factors and may occur through divergent pathways, ultimately linked by ElA. Two independent studies have identified additional factors that interact with early viral promoters. A factor referred to as E4F1 binds to the E4 promoter and also interacts with the EIA, E2A, and E3 promoters (18). Similarly, a factor referred to as E2A-EF binds to the E2A, EIA, E3, and E4 promoters (17). We show here that E4F1 and E2A-EF have the same DNA-binding specificity and that both factors activate transcription of the E4 and E2A promoters in vitro. These results demonstrate that E4F1 and E2A-EF are the same factor, which we refer to as ATF, for activating transcription factor. In addition to the E4 and E2A promoters, ATF interacts with an important functional element of the adenovirus E3 promoter. The interaction of ATF with multiple ElA-inducible promoters suggests a significant role for ATF in E1A-mediated transcriptional activation. MATERIALS AND METHODSPlasmids. pE4WT contains the adenovirus type 5 genome between map units 100 and 89, including the entire E4 gene cloned into pBR322 between the EcoRI and Pvu II sites.

Identification of factors that interact with the E1A-inducible adenovirus E3 promoter.

“…The factor that binds to the -44 to -68 region of E3, which we now call ATF, also binds to critically important regions of the E2A and E4 promoters (Lee et al 1987a). It is possible therefore that this factor plays a crucial role in E1A trans-activation of these early genes.…”

“…Lee and Green (1987)have described a factor, E4.F 1, that binds to at least three regions of the E4 promoter and is also competed by E2 promoter sequences. Subsequent competition assays strongly suggest that E3.F2 and E4.F1 are also the same factor (Lee et al 1987a). The possibility that all three factors are identical is based predominantly on the fact that all three bind an identical DNA sequence.…”

“…Consequently, it cannot be ruled out that each represents a different member of a family of factors that have the same DNA-binding specificity. For the sake of discussion, however, we assume that the factors are identical and have renamed them ATF (Lee et al 1987a}.…”

Cloning and functional characterization of the origin of lytic-phase DNA replication of rat cytomegalovirus.

“…We searched the RCMV ori Lyt region for the presence of these binding sites and found six copies of the ATF\CREB sequence (5h ACGTCA 3h ; Lee et al, 1987 ;Montminy & Bilezikjian, 1987), six copies of the MLTF\USF sequence (5h CGTGAC 3h ; Carthew et al, 1985 ;Sawadago & Roeder, 1985) and 19 copies of the Sp1 sequence (5h CCGCCC 3h ; Briggs et al, 1986 ; Fig. 5 a).…”

Purification of DNA-binding transcription factors by their selective adsorption on the affinity latex particles

“…And they were examined for the ability to purify sequence-specific DNA binding factor, ATF or E4TF3, responsible for transcription of the adenovirus (Ad) early regions, E2, E3 and E4 (2)(3)(4)(5)(6)(7). This factor was quickly and efficiently purified from the extracts of HeLa cells by sequential batch-wise procedures with the affinity latex particles.…”