"There are seven members of the plant specific BBR/BPC-family of transcription factors found in the Arabidopsis genome. The 80 - 90 amino acids at the extreme C-terminus of the protein constitute the highly conserved basic DNA-binding domain (Santi et al., 2003).Functionally, the BBR/BPC-family appears to play a role in the regulation of basal transcription. These proteins were identified initially in soybean by their ability to bind to the (GA/TC)n - dinucleotide repeat enhancer element from the GSA1-promoter (Sangwan and O'Brian, 2002).Analysis of a dominant active mutation in the barley homeobox gene BKn3 resulted in the identification of a transcription factor, named barley B recombinant (BBR), that binds to a (GA/TC)8- dinucleotide repeat in the third intron of BKn3 (Santi et al., 2003). It could be shown that BBR localizes to the nucleus and was able to activate GUS-expression in Nicotiana protoplasts. It was considered that BBR is an essential upstream regulatory factor for proper homeobox gene expression in barley (Santi et al., 2003).This was supported by transgenic tobacco plants overexpressing BBR under the control of the 35S-promoter that resulted in an altered growth and development similar to what one would expect for misexpressed homeotic genes.Binding studies revealed that an essential GA/TC-dinucleotide rich sequence in the promoter of the INNER NO OUTER (INO) gene from Arabidopsis can be targeted by members of this transcription factor family, here named Basic Pentacysteine (BPC) proteins (Meister et al., 2003). Although the protein-family was first named BBR, it was proposed to refer to this family as the BBR/BPC-family of GAGA-binding transcription factors, since "BPC" gives important additional information to its name. So far, all functionally characterized BBR/BPC-proteins are ubiquously expressed in all tissues or developmental stages and do localize to the nucleus (Santi et al.,2003; Meister et al., 2003). Recently, Kooiker et al. (2005) found that two BBR/BPC-family members are involved in the expressional regulation of the homeotic MADS-box gene SEEDSTICK (STK).