The 289-amino acid E1A protein of adenovirus binds zinc in a region that is important for trans-activation.

Abstract

The ElA 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-Xaal3-Cys-Xaa2-Cys) in which the cysteine residues serve as postulated ligands. Atomic absorption spectrophotometry applied to bacterially expressed ElA 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 EMA protein to stimulate transcription of ElA-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 ElA might interact with DNA or protein to bring about trans-activation is discussed.The ElA gene ofadenovirus functions normally by transcriptionally activating (trans-activating) other early viral promoters, which leads to productive infection (1, 2). ElA gene products can also trans-activate the promoters of some cellular genes-e.g., heat shock and f3-tubulin (3, 4)-and, conversely, can repress enhancer-stimulated transcription from the promoters of certain other genes-e.g., immunoglobulin and simian virus 40 early promoters (5-7). How these modes of positive and negative regulation by ElA may be involved in ElA-dependent viral transformation and tumorigenesis (reviewed in ref . 8)

C-terminal-binding protein interacting protein binds directly to adenovirus early region 1A through its N-terminal region and conserved region 3

“…Almost all of the deletions and substitutions introduced into CR3 reduce the interaction with CtIP, suggesting that integrity of the whole region is required for optimal binding (Supplementary Figure 2). However, the major site of interaction on Ad5E1A CR3 appears to be located between amino acids 169-177, which encompasses the two Cterminal cysteines involved in the Zn 2 þ -finger domain (Culp et al, 1988;Webster and Ricciardi, 1991). It is notable that mutation of the two N-terminal cysteines of the Zn 2 þ -finger (for example, in dl 139-160) do not negate CtIP interaction -therefore it seems likely that binding of the metal ion per se is not required for the interaction.…”

“…Binding of the Rb family or CBP/p300 is necessary for AdE1A to promote S phase entry, but binding of both sets of proteins is required for AdE1A-mediated transformation (Egan et al, 1988;Jelmsa et al, 1989;Howe et al, 1990;Wang et al, 1993). CR3 contains a zinc (Zn 2 þ )-finger motif and is the site of interaction with a number of proteins involved in transcriptional regulation (Culp et al, 1988;Geisberg et al, 1994Geisberg et al, , 1995Rasti et al, 2006). These interactions with proteins such as TATA-binding protein (TBP), associated transcription factor (ATFs), suppressor of ras (Sur2) mediator 23 (MED23), proteasomal components and trans-acting factors are necessary for transcriptional activation and for the expression of other viral early region proteins (reviewed by Jones, 1995;Avvakumov et al, 2004).…”

Recent lessons in gene expression, cell cycle control, and cell biology from adenovirus

“…Unlike the situation with many acidic ADs that are random coil until they encounter their protein targets (Radhakrishnan et al, 1997), E1A CR3 appears to be a well-folded globular protein domain. The 40 N-terminal amino acids of CR3 that function as an AD contain four cysteines that chelate a Zn þ 2 ion and are essential for AD function (Culp et al, 1988). Thus, the CR3 AD is a type of Zn-finger, although its structure has not been determined.…”

Comparison of 12 turkey hemorrhagic enteritis virus isolates allows prediction of genetic factors affecting virulence

“…The cysteine-rich motif discovered in the siadenovirus E3 protein resembles the CR3 domain of the mastadenovirus E1A-13S protein. E1A-13S interacts with the TATAbinding protein and other cellular transcription factors and activates transcription of viral genes (Bruder & Hearing, 1989;Culp et al, 1988;Geisberg et al, 1994Geisberg et al, , 1995Parker et al, 1997). E1A-13S activates the tumour necrosis factor (TNF) gene in inflammatory cells, and this activation is dependent on this CR3 domain (Metcalf, 1996).…”