Identification and mapping of Casp7, a cysteine protease resembling CPP32β, interleukin-1β converting enzyme, and CED-3

Cloning of interleukin-1β converting enzyme (ICE) and Caenorhabditis elegans death protein CED-3 revealed the structural and functional homology between these two proteases. It also suggested the involvement of ICE-like cysteine protease in apoptosis. Several CED-3- and ICE-like cysteine proteases have been described, including Nedd2/Ich-1, CPP32β, Tx, ICE(rel)3, and Mch2. We have previously described a mouse ortholog of cysteine protease CPP32β that shares strong homology with ICE and CED-3. Here, we describe the cloning of mouse and human Casp7, another member of this family of cysteine proteases. Mouse Casp7 encodes a putative 340-amino-acid polypeptide that contains all the known conserved residues required for protease function, including the QACRG sequence, aspartic acid residues for internal cleavage sites, and the residues required for substrate binding. Three RNA variants of human Casp7 were also cloned. Amino acid sequence analysis indicated that Casp7 shared high homology with CPP32β/Casp3 and Mch2/Casp6. Northern blot analysis demonstrated that a 2.6-kb Casp7 mRNA was expressed in various tissues except brain. Mouse interspecific backcross mapping allowed localization of Casp7 to the distal region of mouse chromosome 19, linked to Mxi1, Adra2a, and Aop1.