The yeast two-hybrid system was used to investigate dimerization between proteins of Phz2 and Phz4 clones of the homeodomain-leucine zipper family which were obtained by screening a Pimpinella brachycarpa shoot-tip cDNA library. Assays showed that Phz...
The yeast two-hybrid system was used to investigate dimerization between proteins of Phz2 and Phz4 clones of the homeodomain-leucine zipper family which were obtained by screening a Pimpinella brachycarpa shoot-tip cDNA library. Assays showed that Phz4 formed a homo rather than a heterodimer with Phz2. In addition, we isolated cDNA clones, Phybl, Phyb2, and Phyb3, that encode proteins interacting with Phz4. Although Phybl is not a HD-Zip protein, the activity of interaction between Phybl and Phz4 was, surprisingly, stronger than that of the homodimerization of Phz4. The analysis of interacting parts indicated that from 1bp to 466bp of Phybl, there was no interaction with Phz4, but from 467 bp to 593 bp, interactions were found with the N-terminal and C-terminal regions, except for HD-Zip of Phz4. This region of Phybl contained a nuclear localization signal. DMA-binding analysis showed that the Phz4 HD-Zip domain recognized the [T(C/G)ATTG] core sequence and the region containing the [TCATTG] motif, which is, in itself, a promoter in vitro.