Artificial transcription factor

[1] Designed DNA-binding domains, such as CRISPR-Cas, with new targeting capabilities are being explored to engineer higher specificity and control potential side effects.

[2] In the future, ATFs which can respond to physiological cues, only change transcription levels in a specific cell type, and can easily be delivered without the use of electroporation are of great interest.

[1] The clustered regularly interspaced short palindromic repeats - Cas (CRISPR-Cas) system has been extensively studied to target a specific DNA sequence using a single guide RNA (sgRNA).

[2] The CRISPR-Cas system benefits from high specificity between the sgRNA and the target DNA sequence and the simplicity of designing new sgRNAs; however, the CRISPR-Cas system requires a PAM sequence directly upstream of the target DNA site and the large size of the Cas protein hinders delivery into the cell.

[2] Zinc fingers are naturally abundant, involved in multiple regulatory processes, and are common eukaryotic transcriptional factors.

[10] Multiple ATFs composed of three zinc finger proteins linked together can each activate genes that eventually lead to the production of the Oct4 transcription factor in the cell, causing the cell to reprogram to an induced pluripotent state without the addition of external Oct4 transcription factors.

[3] Zinc finger ATF TAT-S1 acts as a strong repressor against the UBE3A-AS gene, and when administered to mice, resulted in increased Ube3a in the brain.

[4] ATFs linked to the KRAB repressor regulatory domain decreases cancer cells' drug resistance to chemotherapy, and ATFs linked to activator domains can upregulate Bax gene expression causing cell apoptosis; however, these treatments remain in the early stages because of inadequate delivery methods.

Figure 1. Example of a natural transcription factor up-regulating gene expression. 1. The transcription factors (labeled activator proteins) bind to their specific DNA sequence (labeled enhancers). 2. The transcription factors recruit other proteins and transcription factors to form a protein complex which binds to the gene promoter. 3. After the activating protein complex binds to the promoter, RNA polymerase easily binds and starts transcribing the target gene. 4. and 5. are additional scenarios where in 4. an insulator/inhibitor can bind to the DNA preventing activation for transcription and in 5. methylation can prevent the insulator from binding.