Molecular cloning and characterization of human Castor, a novel human gene upregulated during cell differentiation.

Castor is a zinc finger transcription factor that controls cell fate within neuroblast cell lineages in Drosophila melanogaster. Here, we describe the cloning and characterization of a human castor gene (CASZ1) that is structurally homologous to Drosophila castor. We find the expression of castor gene is increased when cells of neural origin as well as mesenchymal origin are induced to differentiation. CASZ1 is expressed in a number of normal tissues and exists in at least two mRNA species of 4.4 and 8.0kb. They are named hCasz5 and hCasz11 because the predicted proteins have 5 and 11 zinc fingers, respectively. Deletion analysis of the proximal 5'-flanking sequences delineates sequences sufficient to drive transcription in cells of neural and non-neural origin. Both hCasz5 and hCasz11 localize predominantly in the nucleus, consistent with their role as Zn-finger containing transcription factor. CASZ1 is expressed in a number of human tumors and localizes to a chromosomal region frequently lost in tumors of neuroectodermal origin.