GAGA-motif binding proteins control transcriptional activation or repression of homeotic genes. Interestingly, there are no sequence similarities between animal and plant proteins. Plant BBR/BPC-proteins can be classified into two distinct groups: Previous studies have elaborated on group I members only and so little is known about group II proteins. Here, we focused on the initial characterization of @entity70067 , a group II protein from @entity958 . Comparison of orthologous BBR/BPC sequences disclosed two conserved signatures besides the DNA binding domain. A first peptide signature is essential and sufficient to target @entity70067 -GFP to the nucleus and nucleolus. A second domain is predicted to form a zipper-like coiled-coil structure. This novel type of domain is similar to @entity368 zippers, but contains invariant @entity493 residues with a heptad spacing of 7 @entity1522 . By yeast-2-hybrid and BiFC-assays we could show that this @entity493 zipper domain is essential for homotypic dimerization of group II proteins in vivo. Interhelical salt bridges and charge-stabilized @entity3884 bonds between acidic and basic residues of the two monomers are predicted to form an interaction domain, which does not follow the classical knobs-into-holes zipper model. FRET-FLIM analysis of GFP/RFP-hybrid fusion proteins validates the formation of parallel dimers in planta. Sequence comparison uncovered that this type of domain is not restricted to BBR/BPC proteins, but is found in all kingdoms.

XXXX zipper-like coiled-coil domains are necessary for homotypic dimerization of plant GAGA-factors in the nucleus and nucleolus.

@entity1522 :: ('CHEBI:33709', 'Chemical') :: ['amino acids'] @entity70067 :: ('834259(Tax:3702)', 'Gene') :: ['AtBPC6'] @entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity368 :: ('CHEBI:25017', 'Chemical') :: ['Leucine'] @entity958 :: ('3702', 'Species') :: ['Arabidopsis thaliana'] @entity493 :: ('CHEBI:16449', 'Chemical') :: ['alanine', 'Alanine']
@entity493 :: (CHEBI:16449,Chemical) :: ['Alanine']
