Regulation of gene expression in Arabidopsis thaliana by artificial zinc finger chimeras

The artificial regulation of endogenous gene expression in plants is limited to only a few approaches. Here, we describe the use of artificial zinc finger chimeras to regulate the expression of a known reporter construct. The artificial zinc finger chimera TFIIIAZif is a fusion protein consisting of the four zinc fingers of TFIIIA linked through a spacer region to the three zinc fingers of Zif268. This artificial zinc finger chimera is able to bind specifically to a target DNA sequence (ZBS, zinc finger binding site) of 27 base pairs (bp). TFIIIAZif was fused to a transactivation domain from the herpes simplex virus VP16 or its tetramer VP64 to give ZF-VP16 or ZF-VP64, respectively. In transient expression assays, these two transcription activators were able to activate a target reporter gene (luc and GFP) expressed from a minimal -46 35S promoter linked to four copies of ZBS. The activation was confirmed in transgenic plants using an inducible XVE system [Zuo et al. (2000) Plant J. 24: 265] to express ZF-VP16 or ZF-VP64. Furthermore, to test the specificity of ZF-VP64 we have compared reporter gene expression from a wild type (1xZBS) and a mutant (1xZBSmu) binding site in transgenic plants. The 1xZBS was used to express green fluorescent protein (GFP) whereas the 1xZBSmu was used to express red fluorescent protein (RFP). Upon induction of ZF-VP64 we found a much higher expression of GFP (about 33-fold) as compared to RFP expression. These results suggest that artificial zinc finger chimeras can be used to target specific DNA sequences and to regulate gene expression in plants.