The iDimerize Inducible Expression System can be used to control transcription activation of target genes. Transcription factors are bifunctional proteins that recognize specific DNA sequences near target genes (via the DNA binding domain) and then recruit the transcriptional machinery of the cell to activate transcription (via the transcription activation domain). These two domains can work together to activate transcription even when they are expressed as individual proteins and brought together by the A/C Heterodimerizer ligand.

The iDimerize Inducible Expression System has been designed specifically for use in regulating target genes. The genes encoding the two chimeric transcription factor domains cannot readily be reconfigured for other uses. For other heterodimerization applications, use the iDimerize Inducible Heterodimer System.



Figure 1. Regulated gene expression using the iDimerize Inducible Expression System. Clone your gene of interest downstream of the ZHFD1 inducible promoter (PZI-1). The DNA binding component (DmrC/DNA-BD fusion; red) recognizes and binds sequences within the promoter. However, activation of transcription only occurs when the DmrC/DNA-BD dimerizes with the transcription activation component (DmrA-AD fusion; green) at the promoter, when the DmrA and DmrC domains both bind to the A/C Heterodimerizer (AP21967).

A/C Heterodimerizer Ligand (AP21967)

The A/C Heterodimerizer is a synthetic, cell-permeable ligand that can be used to induce heterodimerization of two fusion proteins, one tagged with the DmrA transcription activation domain (included in this kit) and the other tagged with the DmrC DNA binding domain (included in this kit). The A/C Heterodimerizer is identical to AP21967, which was previously supplied by ARIAD Pharmaceuticals Inc.

Inducible Transcription Kit Components

This application kit is based on three human-based elements:

• Transcription activation component: A single DmrA domain, fused to a transcription activation domain derived from the p65 subunit of NFkappaB
• DNA binding component: A triplet of DmrC domains, fused to a composite DNA binding domain called ZFHD1. ZFHD1 consists of two zinc finger domains from Zif268 joined to a homeodomain from Oct-1
• Inducible promoter component (PZI-1): ZFHD1 binds with high affinity and specificity to 12 repeats of a unique composite ZHFD1 DNA binding sequence, but not to Zif268 or Oct-1 binding sites (1). The binding sites are placed downsteam of a minimal promoter derived from PIL2

Inducing Gene Expression

Sequentially transfect your cells of interest with:

   1. A plasmid which expresses the transcription activation and DNA binding components (either pHet-Act1-1 or pHet-Act2-1)
   2. Your gene of interest cloned downstream of the PZI-1 inducible promoter (in pZFHD1-1)

The DNA binding component remains bound to the promoter at all times, but it cannot activate transcription until it interacts with the transcription activation component via the DmrA and DmrC domains. When the A/C Heterodimerizer is added, the two components interact, and your gene of interest is transcribed from the PZI-1 promoter.



Figure 2. Dose-dependent control of gene expression with the iDimerize Inducible Expression System. HT1080 cells were stably transfected with the secreted alkaline phosphatase (SEAP) reporter gene and the DmrC-AD/DmrA-DBD constructs, and treated with or without A-C Heterodimerizer. In the absence of A-C Heterodimerizer, target gene expression was undetectable. Half-maximal induction occurred at 2 nM A/C Heterodimerizer.

Applications

• Inducing gene expression in a ligand-dependent manner
• Analyzing genes that promote cell death, block the cell cycle, or are otherwise toxic
• Functional genomics research

References

1. Pomerantz, J. L., Sharp, P. A., and Pabo, C. O. (1995) Science 267(5194):93-96. Structure-based design of transcription factors.