Identification of a Brain-specific APC Homologue, APCL, and Its Interaction with /3-Catenin1

We isolated a novel gene, !/'(/. that showed significant homology to the adenomatous polyposis coli (APC} tumor suppressor gene. This novel gene, located on chromosome I9pl3.3, encodes a protein of 2303 amino acids that is expressed specifically in the brain. The predicted protein of APCL contains five copies of a 20-amino-acid motif (FXVEXTPXCFSRXSSLSSLS). Like APC, this domain of APCL was able to bind to ß-catenin and deplete the intracellular ß-catenin pool. A reporter-gene assay re vealed that APCL could also regulate interaction of ß-cateninwith T cellspecific transcription factor, although less actively than APC. These re sults suggest that the APCL protein may be involved in the \ViilAVmgless signal pathway, and the identification of a novel relative of APC may provide new insights into the function of APC.