Part:BBa_K3132000
Gal4-VP64
This part is transformed from the part: Gal4-KRAB(BBa_K2446037) of Igem17_Fudan. To turn this TF into an activating one, we replaced the KRAB domain with a VP64. And this approach successfully reversed its effect as we had expected. Gal4-VP64 containing three core domains from N-terminal to C-terminal: GAL4 DNA binding domain, nuclear location sequence and VP64 transcription regulating domain. And a (G4S) linker was added between DBD and NLS for providing region flexibility. GAL4DBD enable binding to specific DNA sequences, so that we can use Gal4-VP64 as a specific transcription factors to activate the expression of our downstream synthetic promoter elements and minimal CMV.
Usage and Biology
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25INCOMPATIBLE WITH RFC[25]Illegal NgoMIV site found at 41
Illegal NgoMIV site found at 176 - 1000COMPATIBLE WITH RFC[1000]
Contribution
Team: CSU-CHINA 2023
pcDNA3.1(+)-3XHA-GAL4-VP64-NLS
The pcDNA3.1(+)-3×HA-GAL4-VP64-NLS plasmid (BBa_K4585012), which could express GAL4-VP64, was used for Luciferase detection experiment. GAL4 is a protein that can find and bind UAS (upstream activation sequence). VP64 is a transcription factor that, when used in combination with GAL4, can activate UAS and initiate the expression of downstream genes.
pcDNA3.1(+)-3×HA-GAL4-VP64-NLS
The pcDNA3.1(+)-3×HA-GAL4-VP64-NLS plasmid was obtained through homologous recombination of the VP64 homologous recombination insert (BBa_K4585002) with pcDNA3.1(+)-3×HA-GAL4-VP64-NLS linearized vector (BBa_K4585006). The homologous recombination plasmid product was identified as the target product by sequencing and enzyme cutting and agarose gel electrophoresis.
1 Pattern Diagram
Fig.1 The model diagram of pcDNA3.1(+)-3×HA-GAL4-VP64-NLS
2 Experiment
2.1 Method
The pcDNA3.1(+)-3×HA-GAL4-VP64-NLS plasmid could express GAL4-VP64, thereby activating 9×UAS, which could activate the expression of its downstream gene, GAL4-KRAB or Luciferase.
2.2 Results
HEK 293T cells were transiently transfected with GAL-VP64 and GAL-KRAB plasmids, and an appropriate amount of Luciferase plasmids were transfected to simulate GnRH. The experiment showed that the GAL-VP64 plasmid could initiate the expression of GAL4-KRAB and Luciferase.
Fig 2. Bioluminescence intensity when GAL4-VP64=GAL4-KRAB=400 ng
3 Caution
After sequencing and ensuring the sequence was correct, we applied it to the experiments. Store at 4℃.
Contribution
Team: Duke iGEM 2024
Duke iGEM used Gal4-VP64 as a positive control in the testing of the Gal4 Upstream Activating Sequence (UAS). We cloned the Gal4-VP64 into a pcDNA5 backbone with the following primers:
Gal4-VP64_fwd: 5’ - gagctcggatcccgactagtatgaagctgctgagcagc - 3’
Gal4-VP64_rev: 5’ - ctctagactcgagcggccgctcatgatccgagcatgtc - 3’
pcDNA5_fwd: 5’ - GCGGCCGCTCGAGTCTAG - 3’
pcDNA5_rev: 5’ - ACTAGTCGGGATCCGAGCTC - 3’
In our experiments, Gal4-VP64 was designed to be constitutively expressed under the CMV promoter. To validate the part's ability to activate the Gal4 UAS site, we co-transfected pcDNA5-Gal4-VP64 with Gal4 UAS-BFP reporter system into HEK293T cells. The cells were incubated for 48 hours and analyzed using flow cytometry. The results showed an increase in the median BFP fluorescence compared to the negative control (Figure 1), which expressed only the Gal4 UAS-BFP reporter system. The outcome of this experiment successfully validated our approach to use the constitutively active Gal4-VP64 as a positive control in various tests involving the Gal4 UAS site.
Figure 1. Representative histogram of median BFP fluorescence in HEK293T cells co-expressing Gal4-VP64 activator and Gal4 UAS-BFP reporter system. The negative control (NC) cells were transfected with only the Gal4 UAS-BFP reporter system and show lower median fluorescence.
We implemented the Gal4-VP64 positive control in multiple experiments during the development of our ATLAS project. As an example, we investigated the activity of synNotch when exposed to a CD19+ Raji cell line (Figure 2). Thanks to the Gal4-VP64 control, we were able to conclude that our experiments were unsuccessful and further experimental improvements are needed.
Figure 2. An example implementation of the Gal4-VP64 control in an experimental context. The histogram summarizes median BFP fluorescence in HEK293T cells co-transfected with FMC63 synNotch and Gal4 UAS-BFP reporter system. The effector cells were exposed to CD19+ Raji cell line in different E:T ratios (1:10, 1:1, 10:1) 24 hrs post-transfection. The experimental conditions overlap with the negative control (-Raji) and show decreased activation compared to the Gal4-VP64 control.
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