CHK-1 becomes activated in response to DNA damage and prevents damaged cells from progressing though S phase or entering into mitosis in yeast and mammalian cells. To determine biological functions of Ce-CHK-1, a Caenorhabditis elegans checkpoint kinase 1 encoded by the open reading frame Y39H10A.7a, we investigated C. elegans phenotypes induced by inhibition of the
chk-1 gene expression. Ce-CHK-1 was immuno-localized to the nuclei of embryonic, intestinal, and germ cells. When the
chk-1 gene expression was inhibited by RNA interference(RNAi), various phenotypes including ruptured body, bag of worms, and defects in male ray formation appeared, and penetrance of hethese phenotypes was higher at an increased growth temperature. Occurrence of these phenotypes synergistically was increased by UV-irradiation, suggesting that Ce-CHK-1 is involved in the cellular response to DNA damage. In addition, fast larval development of
chk-1(RNAi) strain was observed, which was not affected by UV-irradiation, in contrast to growth retardation of wild type worms by UV-irradiation. We are currently characterizing the phenotypes of
chk-1(
tm0938) strain such as larval arrest.
crn-1(cell death related nuclease 1) is a C. elegans homolog of yeast flap endonuclease 1(
fen-1) which is involved in the processing of replication intermediates. CRN-1 was immuno-localized to the nuclei of embryonic cells, mitotic germ cells, and oocytes. In order to study the interaction between
crn-1 and checkpoint genes including
chk-1, double RNAi was performed on
crn-1 and one of the checkpoint genes such as
atm-1(Y48G1BL.2),
atl-1(T06E4.3a),
cep-1/p53(F52B5.5) or
chk-1(Y39H10A.7). The embryonic lethality due to
crn-1 (RNAi) was recovered by simultaneous RNAi of above checkpoint genes. These results suggest that DNA replication intermediates produced by
crn-1 (RNAi) result in embryonic lethality probably by inducing cell cycle arrest through a checkpoint pathway.