The N termini of Friend of GATA (FOG) proteins define a novel transcriptional repression motif and a superfamily of transcriptional repressors.

Members of the Friend of GATA (FOG) family of transcriptional co-factors are required for the development of both the cardiovascular and hematopoietic systems. FOG proteins physically interact with members of the GATA family of transcriptional activators and modulate their activity. We have previously shown that FOG-2 can bind to the N-terminal zinc finger of GATA4 and, via this interaction, repress GATA4-mediated transcriptional activation of various cardiac promoters. In this report we further characterize the domain of FOG-2 necessary for repression of GATA4 transcriptional activity. We show that FOG-2-mediated repression is not blocked by the histone deacetylase inhibitor tricostatin A, suggesting that FOG-2 repression of GATA4 occurs via a histone deacetylase independent mechanism. N-terminal deletion mutants of FOG-2 revealed that the first 12 amino acids of FOG-2 are necessary for FOG-2-mediated repression. Fusion of these 12 amino acids to the DNA binding domain of GAL4 demonstrated that this region is sufficient to mediate transcriptional repression even when recruited to a heterologous promoter. Single amino acid substitutions within this N-terminal domain of FOG-2 defined the critical amino acid sequence as RRKQxxPxxI. Interestingly, a search of the NCBI protein data base identified several other partially characterized zinc finger transcriptional repressors from various vertebrate species that contained this motif at their N terminus. Taken together, these observations define a novel transcriptional repression motif and a superfamily of zinc finger transcriptional repressors.