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

AUTOR(ES)

Culp, J S

RESUMO

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.

Documentos Relacionados

• Cyclic AMP induction of early adenovirus promoters involves sequences required for E1A trans-activation.
• The adenovirus E4 gene, in addition to the E1A gene, is important for trans-activation of E2 transcription and for E2F activation.
• Induction of c-fos mRNA and AP-1 DNA-binding activity by cAMP in cooperation with either the adenovirus 243- or the adenovirus 289-amino acid E1A protein.
• The functional importance of a cap site-proximal region of the human prointerleukin 1 beta gene is defined by viral protein trans-activation.
• An adenovirus type 5 E1A protein with a single amino acid substitution blocks wild-type E1A transactivation.