Can AtTZF1 act as a transcriptional activator or repressor in plants?

In animals, Tandem CCCH Zinc Finger (TZF) proteins can affect gene expression at both transcriptional and post-transcriptional levels. In Arabidopsis thaliana, AtTZF1 is a member of the TZF family characterized by a plant-unique tandem zinc finger motif. AtTZF1 can bind both DNA and RNA in vitro, and it can traffic between the nucleus and cytoplasmic foci. However, no in vivo DNA/RNA targets have been identified so far, and little is known about the molecular mechanisms underlying AtTZF1's profound effects on plant growth, development, and stress responses. In order to determine whether AtTZF1 can function as a transcription factor, transactivation assays were conducted. Results indicated that AtTZF1 fusion proteins could not exert obvious transcriptional activity in a maize protoplast transient expression system. However, this conclusion might be biased due to poor nuclear localization of AtTZF1 fusion proteins in the assay system.