The fold recognition of CP2 transcription factors gives new insights into the function and evolution of tumor suppressor protein p53.

The CP2 transcription factor (TFCP2) is a critical regulator of erythroid gene expression. Apart from the involvement in the transcriptional switch of globin gene promoters it activates an array of cellular and viral gene promoters. A number of homologous proteins was identified in genomes of Metazoa, with additional five homologues encoded by the human genome (TFCP2L1, UBP1, GRHL1, GRHL2, GRHL3). Although several experimental studies have already been published, the knowledge on the molecular mechanism of activity of this transcription factors remains very limited. Here we present the application of fold recognition and protein structure prediction in drafting the structure-to-function relationship of the CP2 family. The employed procedure clearly shows that the family adopts a DNA binding immunoglobulin fold homologous to the p53 (TP53) core domain, and a novel type of ubiquitin-like domain and a sterile alpha motif (SAM) form oligomerization modules. With a traceable evolution of CP2 family throughout the Metazoa group this protein family is highly likely to represent an ancestor of the critical cell cycle regulator p53. Based on this observation several functional hypotheses on structure-to-function relationship of p53 were drawn. The DNA motif recognized by p53 is a result of further specialization of the CP2 DNA-binding module. The analysis also shows the critical role of protein oligomerization for the function of this protein superfamily. Finally, the identification of distant homologs of TP53 allowed performing a phylogenetic footprinting analysis explaining the role of the specific amino acids important for both - the protein folding and the binding of DNA.