Abstract: The present invention provides isolated and substantially purified nucleic acids encoding human Jade-1 (for “gene” for Apoptosis and Differentiation in Epithelia) and related nucleic acids. The invention further provides Jade protein, which, when expressed in a eukaryotic cell, has an apparent molecular weight of 64 kD. We have discovered that Jade protein functions 1 apoptosis and regulation of cell cycle as well as in cellular differentiation process. Accordingly, the Jade-family of genes and their gene products provide novel diagnostic and prognostic tools for identifying and/or classifying diseases involving abnormal apoptosis and defective cell cycle.