Helicase-related proteins play crucial roles in nucleic acids- and chromatin-mediated reactions such as DNA replication, DNA repair, pre-mRNA splicing, or chromatin remodeling. Dysfunctions of human WRN and BLM helicases cause accelerated aging and various cancers, respectively. Considering biological importance of this family, we have previously characterized loss-of-function phenotypes in RNAi-treated C. elegans for helicase-related genes by feeding method. In this study, we identified the D2005.5 (
drh-3) gene in an RNAi-based screen for genes involved in resistance to X-ray irradiation. Recently, it has been reported that
drh-3 plays a role in RNA interference (Duchaine et al., Cell 124, 343, 2006) and it is interesting to study the functional relationship between RNAi and maintenance of genome stability. Here, we report phenotypic characterization of
drh-3(RNAi) animals. The
drh-3 gene encodes a novel RNA helicase-like protein that is similar to two nematode Dicer-related helicases. We characterized the phenotype of
drh-3-interferred nematodes using feeding RNAi. RNAi-mediated depletion of the
drh-3 transcripts caused embryonic lethality of F1 progeny and temperature-sensitive reproductive capacity, but did not affect the nematode lifespan. F1 progeny from
drh-3(RNAi) animals exhibited increased lethality as observed in
rad-51(RNAi) progeny after X-ray irradiation or exposure to camptothecin. In both
drh-3(RNAi) and
rad-51(RNAi) worms, unusual-shaped and aggregated chromosomes were observed in diakinesis oocyte nuclei. In developing early zygotic embryos from
drh-3(RNAi) worms, abnormally divided nuclei were observed and embryonic development was largely arrested in embryogenesis. Finally, examination of checkpoint responses in mitotic germ cells with regards to replication arrest by hydroxyurea and X-ray-induced DNA damage suggested that both checkpoints function normally under these genotoxic stress conditions. These results indicate that the
drh-3 gene is essential for the development of germ lines by maintaining chromosomal integrity in C. elegans.