title: Single zinc-finger extension: enhancing transcriptional activity and specificity of three-zinc-finger proteins.
abstract: In order to demonstrate that an existing zinc-finger protein can be simply modified to enhance DNA binding and sequence discrimination in both episomal and chromatin contexts using existing zinc-finger DNA recognition code data, and without recourse to phage display and selection strategies, we have examined the consequences of a single zinc-finger extension to a synthetic three-zinc-finger VP16 fusion protein, on transcriptional activation from model target promoters harbouring the zinc-finger binding sequences. We report a nearly 10-fold enhanced transcriptional activation by the four-zinc-finger VP16 fusion protein relative to the progenitor three-finger VP16 protein in transient assays and a greater than five-fold enhancement in stable reporter-gene expression assays. A marked decrease in transcriptional activation was evident for the four-zinc-finger derivative from mutated regulatory regions compared to the progenitor protein, as a result of recognition site-size extension. This discriminatory effect was shown to be protein concentration-dependent. These observations suggest that four-zinc-finger proteins are stable functional motifs that can be a significant improvement over the progenitor three-zinc-finger protein, both in terms of specificity and the ability to target transcriptional function to promoters, and that single zinc-finger extension can therefore have a significant impact on DNA zinc-finger protein interactions. This is a simple route for modifying or enhancing the binding properties of existing synthetic zinc-finger-based transcription factors and may be particularly suited for the modification of endogenous zinc-finger transcription factors for promoter biasing applications.
authors.affiliation: Department of Haematological and Molecular Medicine, Guy's, King's and St. Thomas' School of Medicine, The Rayne Institute, 123 Coldharbour Lane, London SE5 9NU, UK.
authors.forename: Alexander E F
authors.initials: AE
authors.lastname: Smith
authors.forename: Farzin
authors.initials: F
authors.lastname: Farzaneh
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Ford
mesh_terms: D001483:Base Sequence; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D015202:Protein Engineering; D015533:Transcriptional Activation; D016335:Zinc Fingers / Q000502:physiology*
chemical_list: D016044:Fusion Proteins, bcr-abl