Zinc finger transcription factors or ZF-TFs, are transcription factors composed of a zinc finger-binding domain and any of a variety of transcription-factor effector-domains that exert their modulatory effect in the vicinity of any sequence to which the protein domain binds. [1]
Zinc finger protein transcription factors can be encoded by genes small enough to fit a number of such genes into a single vector, allowing the medical intervention and control of expression of multiple genes and the initiation of an elaborate cascade of events. In this respect, it is also possible to target a sequence that is common to multiple (usually functionally related) genes in order to control the transcription of all these genes with a single transcription factor. Also, it is possible to target a family of related genes by targeting and modulating the expression of the endogenous transcription factor(s) that control(s) them. They also have the advantage that the targeted sequence need not be symmetrical unlike with most other DNA-binding motifs based on natural transcription factors that bind as dimers. [1]
By targeting the ZF-TF toward a specific DNA sequence and attaching the necessary effector domain, it is possible to downregulate or upregulate the expression of the gene(s) in question while using the same DNA-binding domain. [2] The expression of a gene can also be downregulated by blocking elongation by RNA polymerase (without the need for an effector domain) in the coding region or alternatively, RNA itself can also be targeted. [1] [3] Besides the obvious development of tools for the research of gene function, engineered ZF-TFs have therapeutic potential including correction of abnormal gene expression profiles (e.g., erbB-2 overexpression in human adenocarcinomas) [4] [5] and anti-retrovirals (e.g. HIV-1 [6] ).
A zinc finger is a small protein structural motif that is characterized by the coordination of one or more zinc ions (Zn2+) in order to stabilize the fold. It was originally coined to describe the finger-like appearance of a hypothesized structure from the African clawed frog (Xenopus laevis) transcription factor IIIA. However, it has been found to encompass a wide variety of differing protein structures in eukaryotic cells. Xenopus laevis TFIIIA was originally demonstrated to contain zinc and require the metal for function in 1983, the first such reported zinc requirement for a gene regulatory protein followed soon thereafter by the Krüppel factor in Drosophila. It often appears as a metal-binding domain in multi-domain proteins.
Zinc finger protein GLI1 also known as glioma-associated oncogene is a protein that in humans is encoded by the GLI1 gene. It was originally isolated from human glioblastoma cells.
The C7.GAT protein is a zinc finger protein based on the C7 protein. It features an alternative zinc finger 3 alpha helix sequence, preventing the target site overlap caused by the aspartic acid residue of the finger 3 of C7. The sequence of this third finger is TSG-N-LVR according to the single letter amino acid code. As the name suggest, the target site of finger 3 is altered to 5'-GAT-3', giving the overall protein a target of 5'-GCGTGGGAT-3'.
Therapeutic gene modulation refers to the practice of altering the expression of a gene at one of various stages, with a view to alleviate some form of ailment. It differs from gene therapy in that gene modulation seeks to alter the expression of an endogenous gene whereas gene therapy concerns the introduction of a gene whose product aids the recipient directly.
In a zinc finger protein, certain sequences of amino acid residues are able to recognise and bind to an extended target-site of four or even five nucleotides When this occurs in a ZFP in which the three-nucleotide subsites are contiguous, one zinc finger interferes with the target-site of the zinc finger adjacent to it, a situation known as target-site overlap. For example, a zinc finger containing arginine at position -1 and aspartic acid at position 2 along its alpha-helix will recognise an extended sequence of four nucleotides of the sequence 5'-NNG(G/T)-3'. The hydrogen bond between Asp2 and the N4 of either a cytosine or adenine base paired to the guanine or thymine, respectively defines these two nucleotides at the 3' position, defining a sequence that overlaps into the subsite of any zinc finger that may be attached N-terminally.
T-cell acute lymphocytic leukemia protein 1 is a protein that in humans is encoded by the TAL1 gene.
Nucleosome-remodeling factor subunit BPTF is a protein that in humans is encoded by the BPTF gene.
Zinc finger protein 281 is a protein that in humans is encoded by the ZNF281 gene.
Zinc finger protein 40 is a protein that in humans is encoded by the HIVEP1 gene.
Zinc finger and BTB domain-containing protein 7A is a protein that in humans is encoded by the ZBTB7A gene.
Early growth response protein 3 is a protein in humans, encoded by the EGR3 gene.
Zinc finger protein chimera are chimeric proteins composed of a DNA-binding zinc finger protein domain and another domain through which the protein exerts its effect. The effector domain may be a transcriptional activator (A) or repressor (R), a methylation domain (M) or a nuclease (N).
Zinc finger protein 161 homolog is a protein that in humans is encoded by the ZFP161 gene.
Zinc finger and BTB domain-containing protein 7B is a protein that in humans is encoded by the ZBTB7B gene. ZFP67 is an early growth response gene that encodes a zinc finger-containing transcription factor that binds to the promoter regions of type I collagen genes and has a role in development.[supplied by OMIM]
Zinc finger protein 19 is a protein that in humans is encoded by the ZNF19 gene.
Transcriptional repressor CTCFL also known as BORIS is a protein that in humans is encoded by the CTCFL gene.
Zinc finger protein 16 is a protein that in humans is encoded by the ZNF16 gene.
Zinc finger protein 224 is a protein that in humans is encoded by the ZNF224 gene.
Zinc finger and BTB domain-containing protein 40 is a protein that in humans is encoded by the ZBTB40 gene.
Early growth response protein 4 (EGR-4), also known as AT133, is a protein that in humans is encoded by the EGR4 gene.