Functional characterization of Caenorhabditis elegans DNA topoisomerase III alpha

To investigate the function of a DNA topoisomerase III enzyme in Caenorhabd itis elegans, the full-length cDNA of C. elegans DNA topoisomerase III alph a was cloned. The deduced amino acid sequence exhibited identities of 48 an d 39% with those of human DNA topoisomerase III alpha and Saccharomyces cer evisiae DNA topoisomerase III, respectively. The overexpressed polypeptide showed an optimal activity for removing negative DNA supercoils at a relati vely high temperature of 52-57 degrees C, which is similar to the optimum t emperatures of other eukaryotic DNA topoisomerase III enzymes. When topoiso merase III alpha expression was interfered with by a cognate double-strande d RNA injection, pleiotropic phenotypes with abnormalities in germ cell pro liferation, oogenesis and embryogenesis appeared. These phenotypes were wel l correlated with mRNA expression localized in the meiotic cells of gonad a nd early embryonic cells.