An adenovirus early region 4 gene product is required for induction of the infection-specific form of cellular E2F activity.

Abstract

E2F is a cellular, sequence-specific DNA-binding factor that binds to pairs of sites that occur upstream of the E1A and E2 early mRNA cap sites. During adenovirus infection, there is induction of a form of E2F that binds cooperatively to the pair of sites in the E2 control region. Production of the infection-specific E2F activity is dependent on early region 4 (E4), as extracts of cells infected with a mutant that lacks E4 did not contain this activity. Instead, two new forms of E2F were seen with the E4 mutant. Infection with mutant viruses unable to make E1A gene products produced the wild-type infection-specific E2F activity after a delay. Mutations in the E1B-55 kD-, E1B-21 kD-, E2-72 kD-, and E3-coding regions had no effect on production of infection-specific E2F. Analysis of cell lines confirmed the results obtained with mutant viruses. Cells that expressed E1A but not E4 genes (e.g., 293 cells) did not contain infection-specific E2F. Cell lines that expressed the E4 gene contained the activity. These observations demonstrate that E4 participates in the infection-induced change in E2F-binding activity. The data are consistent with E1A playing an indirect role in the process by mediating the efficient expression of E4 gene products which, in turn, induce the alteration in E2F activity.

Adenoviruses increase endothelial cell proliferation, migration, and tube formation: Partial reversal by the focal adhesion kinase inhibitor, FRNK

“…This region contains seven open reading frames (Shenk, 1996). The E4ORF4 protein activates protein phosphatase 2A (Kleinberger and Stenk, 1993) and may regulate DNA synthesis and AP-1 activity (Muller et al, 1992), E4ORF6 inhibits p53-mediated transcription (Dobner et al, 1996), and E4ORF6/7 promotes E2 promoter activity (Hardy et al, 1989). As such, these genes may cooperate to induce adenovirus mediated survival and gene expression in endothelial cells.…”

Decreased Replication Ability of E1-Deleted Adenoviruses Correlates with Increased Brain Tumor Malignancy

“…The host cell restricted DNA replication defects of H5dl312 and H5dl434 could be a direct result of not being able to release E2Fs from pRB. In addition, the adenovirus E4 ORF6/7 protein cooperates with free E2F to enhance transcription from the E2A promoter (47). It is possible that transcription of E4ORF6/7 was absent or severely diminished in low passage number anaplastic astrocytomas and glioblastomas.…”

Domains of the adenovirus E1A protein required for oncogenic activity are also required for dissociation of E2F transcription factor complexes.

“…In a lytic viral infection, the release of E2F from these complexes allows the 19-kD product of the early E4 gene to interact with E2F and facilitate the formation of a stable complex on the E2 promoter (Hardy et al 1989;Huang and Hearing 1989;Raychaudhuri et al 1990), a process that further enhances E2 transcription (Babiss 1989;Reichel et al 1989;Neill et al 1990). We believe that the variation from experiment to experiment in m a n y past reports is probably a function of the target promoter.…”

“…A series of recent experiments have demonstrated that a product of the adenovirus early E4 transcription unit forms a complex with the cellular E2F transcription factor to allow cooperative binding at the E2 promoter (Hardy et al 1989;Huang and Hearing 1989;Reichel et al 1989;Marton et al 1990;Neill et al 1990;Raychaudhuri et al 1990). The binding of E2F/E4 complexes at adjacent promoter sites generates a very stable DNA complex and ultimately a stimulation of E2 transcription.…”