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In the course of systematic RNA interference (RNAi)-based screens with helicase-like genes in Caenorhabditis elegans, we have identified the drh-3( D2005.5) gene as a candidate gene for protection against X-ray irradiation. This gene encodes a novel RNA helicase-like protein that is similar to two nematode Dicer-related helicases (DRH). Here, we have showed the increased expression of drh-3 transcripts during maturation of larvae to adults, and characterized the phenotype of drh-3-interferred nematodes using feeding RNAi method. 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 life span. F1 progeny from drh-3( RNAi) animals exhibited increased lethality after X-ray irradiation or exposure to camptothecin. In drh-3( RNAi) worms, aggregated chromosomes were observed in diakinesis oocyte nuclei. In developing early zygotic embryos from drh-3( RNAi) worms, abnormally segregated chromosomes were observed and embryonic development was largely arrested at the mid-stages of 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. Taken together, these results indicate that the drh-3 gene is essential for the development of germ-lines by maintaining chromosomal integrity in C. elegans. [ABSTRACT FROM AUTHOR]