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10x[TALA+TALB] operator_CMV promoter_fLuciferase

TALA and TALB labels represents TAL effectors 1257 and 1297 respectively from zebrafish experiments (Sander et al., 2011)

Introduction

Transcription activation like (TAL) effectors are bacterial plant pathogen transcription factors that bind to DNA by recognizing a specific DNA sequence in which each base pair is bound by a single tandem repeat in the TAL DNA-binding domain. A tandem TAL repeat contains 33 to 35 amino acids, where the 12th and the 13th amino acid, called a “repeat variable diresidue” (RVD) are responsible for specific interactions with the corresponding base pair (Scholze and Boch, 2011). All TAL repeats have almost identical sequences, differing only in the RVDs. This modularity of TAL effector binding domains therefore makes them a perfect tool to target specific DNA sequences by designing specific binding domains for a selected TAL effector.

We designed our construct with 10 alterations of binding sites for TALA and TALB (10×[A + B), upstream of a CMV promoter (constitutive promoter for expression in mammalian cells). Downstream of the promoter we cloned fLuciferase (firefly luciferase) to function as a reporter.

Figure1:Schematic representation of our construct

Characterisation

HEK293T cells were transfected with the 10x[TALA+TALB] operator_CMV promoter_fLuciferase reporter and TALA:NLS:KRAB or TALB:NLS:KRAB (Figure 2). Tests showed, successful repression of fLuciferase with either TAL repressor.

Figure 2:Schematic representation of repression experiments. A: in the absence of a TAL repressor, the reporter gene is constituitively expressed. B: when a TAL repressor is present, it binds to its respective binding site upstream of the CMV promoter and represses transcription of the reporter gene with the KRAB domain.

Figure 3: Repression of luciferase reporter. Control: 10x[TALA+TALB] operator_CMV promoter_fLuciferase without TAL:NLS:KRAB

• fLuciferase was contributed by host lab
• Binding sites for TAL effectors were ordered from IDT.

References

Sander, J. D., Cade, L., Khayter, C., Reyon, D., Peterson, R. T., Joung, J. K., and Yeh, J.-R. J. (2011) Targeted gene disruption in somatic zebrafish cells using engineered TALENs. Nature Biotechnology 29, 697–698

Scholze, H., and Boch, J. (2011) TAL effectors are remote controls for gene activation. Curr. Opin. Microbiol. 14, 47-53

Sequence and Features