title: Regulation of gene expression, cellular localization, and in vivo function of Caenorhabditis elegans DNA topoisomerase I.
abstract: BACKGROUND
  DNA topoisomerase I is dispensable in yeast, but is essential during the embryogenesis of Drosophila and mouse. In order to determine functions of the enzyme in the development of Caenorhabditis elegans, phenotypes resulting from the deficiency were observed and correlated with the expression 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 appeared at the comma stage of embryos, continued through the L1 larval stage, and began to decrease gradually afterwards. The DNA topoisomerase I protein was immuno-localized in the nuclei of meiotic gonad cells and interphase embryonic cells, and unexpectedly in centrosomes of mitotic embryonic cells. Double-stranded RNA interference of DNA topoisomerase I gene expression resulted in pleiotropic phenotypes showing abnormal gonadogenesis, oocyte development and embryogenesis.
  
  
  CONCLUSIONS
  These phenotypes, along with expressional regulations, demonstrate that DNA topoisomerase I plays important roles in rapidly growing germ cells and embryonic cells.
authors.affiliation: Department of Biochemistry, College of Science, Yonsei University, Seoul 120-749, Korea.
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
authors.forename: H
authors.initials: H
authors.lastname: Park
authors.forename: G
authors.initials: G
authors.lastname: Shim
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.forename: H S
authors.initials: HS
authors.lastname: Koo
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000201:enzymology; D004264:DNA Topoisomerases, Type I / Q000235:genetics* / Q000502:physiology; D016054:DNA, Protozoan / Q000235:genetics* / Q000502:physiology; D005697:Galactosides; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D005822:Genetic Vectors; D006066:Gonads / Q000166:cytology / Q000378:metabolism; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D007211:Indoles; D007763:Lac Operon / Q000502:physiology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D016054:DNA, Protozoan; D005697:Galactosides; D007211:Indoles; D012333:RNA, Messenger; D004264:DNA Topoisomerases, Type I; C044888:5-bromo-4-chloro-3-indolyl beta-galactoside