All-1 Interacts With Unr, A Protein Containing Multiple Cold Shock Domains

The ALL-1 gene is involved in human acute leukemia through chromosome translocations and fusion to partner genes, or through partial tandem duplications, ALL-1 is the human homologue of Drosophila trithorax which transregulates the homeotic genes of the Antennapedia and bithorax complexes controlling body segment identity, ALL-1 encodes a very large protein of 3968 amino acids which presumably interacts with many proteins, Here we applied yeast two hybrid screening to identify proteins interacting with the N-terminal segment of ALL-1, One protein obtained in this way was the product of the unr gene, This protein consists of multiple repeats homologous to the cold shock domain (CSD), a motif common to some bacterial and eukaryotic nucleic acids-binding proteins, The minimal region on unr required for the interaction with ALL-1 included two CSD and two intervening polypeptides. The interaction was confirmed by in vitro binding studies, and by coimmunoprecipitation from COS cells overexpressing the relevant segments of the two proteins, These results suggest that unr is involved in an interaction of ALL-1 with DNA or RNA.