Mh. Lee et al., Regulation of gene expression, cellular localization, and in vivo functionof Caenorhabditis elegans DNA topoisomerase I, GENES CELLS, 6(4), 2001, pp. 303-312
Background: DNA topoisomerase I is dispensable in yeast, but is essential d
uring the embryogenesis of Drosophila and mouse. In order to determine func
tions of the enzyme in the development of Caenorhabditis elegans, phenotype
s resulting from the deficiency were observed and correlated with the expre
ssion of the gene.
Results: The transcriptional regulation of the C. elegans DNA topoisomerase
I gene was investigated by mRNA localization and reporter gene expression
in C. elegans. The mRNA was expressed in the gonad and in the early embryos
, followed by a rapid decrease in its level during the late embryonic stage
. A reporter gene expression induced by the 5'-upstream DNA sequence appear
ed at the comma stage of embryos, continued through the L1 larval stage, an
d began to decrease gradually afterwards. The DNA topoisomerase I protein w
as immuno-localized in the nuclei of meiotic gonad cells and interphase emb
ryonic cells, and unexpectedly in centrosomes of mitotic embryonic cells. D
ouble-stranded RNA interference of DNA topoisomerase I gene expression resu
lted in pleiotropic phenotypes showing abnormal gonadogenesis, oocyte devel
opment and embryogenesis.
Conclusion: These phenotypes, along with expressional regulations, demonstr
ate that DNA topoisomerase I plays important roles in rapidly growing germ
cells and embryonic cells.