The protein encoded by the open reading frame F08B4.1 was found to interact with a RecQ family DNA helicase (RecQ5) encoded by E03A3.2 in yeast two-hybrid assay. The gene product of F08b4.1 is homologous to human DICE-1 protein, which was first identified in a human lung carcinoma cell as a candidate tumor suppressor. Although human DICE-1 (deleted in cancer 1) is presumed to be a tumor suppressor, its detailed molecular function is unknown. We have examined the functions and expression pattern of Ce-Dice-1 by RNA interference and GFP reporter expression. When the
Ce-dice-1 was inhibited by double-stranded RNA microinjection, complete embryonic lethality was observed. In order to examine the functions of Ce-Dice-1 at postembryonic stage,
Ce-dice-1 gene expression was inhibited by feeding Caenorhabditis elegans worms with the double-stranded RNA from the L1 stage. Protruding vulva, growth arrest at the L4 stage, and pleiotropic phenotypes in the germ-line such as undersized gonads, abnormal gonad migration, defective oocyte development, endomitotic oocytes, and increased apoptosis appeared. GFP reporter gene expression induced by the promoter sequence was observed in hypodermal cells after the L4 stage. The gene expression in hypodermal cells probably is associated with the phenotypes of protruding vulva and growth arrest at the L4 stage.
Ce-dice-1 is probably also expressed in the germ-line and early embryos, as deduced from the RNAi phenotypes. Although, Ce-Dice-1 interacts with RecQ5 protein in yeast two-hybrid assay, no genetic interaction has been detected in double RNAi of the two genes.