Isolation and Identification of the Human Homolog of a New p53-Binding Protein, Mdmx

Abstract

We recently reported the identification of a mouse cDNA encoding a new p53-associating protein that we called Mdmx because of its structural similarity to Mdm2, a well-known p53-binding protein. Here we report the isolation of a cDNA encoding the human homolog of Mdmx. The ORF of the cDNA encodes a protein of 490 amino acids, 90% similar to mouse Mdmx. The homology between Mdmx and Mdm2 is most prominent in the p53-binding domain and the putative metal-binding domains. The Mdmx protein, which, based on SDS–PAGE, has a MW of 80 kDa, can bind p53in vitro.The humanMDMXgene is transcribed in all tissues tested, with high levels in thymus. By fluorescencein situhybridization analysis we mapped the mousemdmxgene to chromosome 1 (region F–G) and the humanMDMXgene to chromosome 1q32.