Highly conserved C terminus, but lack the G/F-rich and CRR domains. Hahn et al. (1999) identified a J domain-containing protein in mouse and Drosophila. By database searching for sequences homologous to these proteins, Lee et al. (2000) identified a human homolog, which they designated JDP1, that has 2 isoforms generated by alternative use of polyadenylation sites. The primary isoform is 1.2 kb long and encodes a 198-amino acid protein; the other is 0.7 kb long and encodes a 107-amino acid protein. The 198-amino acid protein shares approximately 77% sequence identity with the mouse protein. Northern blot analysis detected a single transcript of 1.3 kb at high levels in brain, heart, and testis, and at reduced levels in kidney and stomach. In mouse and Drosophila, expression is highest in kidney and restricted to heads, respectively.