SCHISTOSOMA-MANSONI - CLONING AND CHARACTERIZATION OF A GENE ENCODINGCYTOSOLIC CU ZN SUPEROXIDE-DISMUTASE/

Two forms of Cu/Zn superoxide dismutase (SOD) have been identified in Schiatosoma mansoni, signal peptide containing SOD (SP-SOD, Simurda et al., 1988, Exp. Parasitol. 67, 73-84) and cytosolic SOD (CT-SOD, Hong et al., 1992, Exp. Parasitol. 75, 308-322). The SP-SOD gene has been previously characterized. We report the isolation and characterization of the gene encoding CT-SOD. A cDNA clone of CT-SOD was radiolabeled and used to screen an EMBL3 genomic library. Of 100,000 plaques, 1 hyb ridizing phage contained an insert of 14.6 kb. The CT-SOD gene spans 8 .5 kb of chromosomal DNA and possesses three exons (150, 285, and 234 bp, respectively) and two introns (4.9 and 2.7 kb, respectively) which interrupt the coding region. Separate copies of the gene as determine d by restriction fragment patterns on Southern blots are found on two YAC clones. Using YAC clones that contain the CT-SOD gene, fluorescenc e in situ hybridization on chromosomes identified a copy of the gene l ocated on the middle region of chromosome 1 and another copy localized to the middle region of the long arm of chromosome 3. Primer extensio n and nuclease protection assay performed on total RNA define the tran scription initiation site and allow the identification of potential ci a-acting sequences, such as a CAAT box and a hexanucleotide GCCCGG. Co mparison of this gene with Cu/Zn SOD genes from Drosophila, humans, an d mice identifies conserved exons that represent functional domains in the SOD protein. (C) 1995 Academic Press, Inc.