Non-sequence-specific DNA binding by the FILAMENTOUS FLOWER protein from Arabidopsis thaliana is reduced by EDTA

The FILAMENTOUS FLOWER protein has a zinc finger domain, hydrophobic region, proline-rich region, and a HMG box-like domain. We have reported that zinc release at the zinc finger is probably facilitated by the non-canonical cysteine residue at position 56, and that EDTA causes the structural change and enhances the self-assembly of the protein (Kanaya, E., Watanabe, K., Nakajima, N., Okada, K., and Shimura, Y. (2001) J. Biol. Chem. 276, 7383-7390). To investigate this aspect further we examined the DNA binding function of the FILAMENTOUS FLOWER protein. Gel retardation experiments showed that the FILAMENTOUS FLOWER protein binds to DNA without sequence specificity. Deletion analyses suggested that the zinc finger domain and the hydrophobic region are not required but the proline-rich region and the HMG box-like domain are indispensable for the DNA binding by the FILAMENTOUS FLOWER protein. The DNA binding by the protein consisting of the zinc finger domain and the rest of the regions was reduced with the addition of EDTA. This result probably suggests that the zinc release, the structural change probably occurring in the zinc finger domain, the intermolecular interaction, and the self-assembly of the protein are related to the dissociation of the FILAMENTOUS FLOWER protein from DNA.