Cloning, characterization, and expression of human LIG1

Growth factor receptors are frequently amplified and over-expressed in vari ous human cancers. Recently, a Drosophila cell surface protein, Kekkon-1, w as found to participate in an epidermal growth factor (EGF) driven negative feedback loop. Kekkon-1 is induced by EGF, binds to the EGF-receptor, and inhibits receptor-mediated signaling. Here, we have searched for human gene s with homologies to Kekkon-1 and identified human LIG1. The gene is the hu man homologue of mouse Lig-1 and is located on chromosome band 3p14, a regi on frequently deleted in various human cancers. It is predicted to encode a transmembrane cell-surface protein with extracellular leucine-rich repeats and immunoglobulin-like domains. LIG1 mRNA was detected in all tissues ana lyzed. The highest and lowest relative expression levels were found in brai n and spleen, respectively, and differed by more than 200-fold. Taken toget her, our data are compatible with a role for LIG1 as a growth tumor suppres sor in human tissues. (C) 2001 Academic Press.