Bloom's syndrome is an autosomal recessive human genetic disorder, characterized by a high incidence of cancer, growth retardation, and immunodeficiency. BLM, the gene mutated in Bloom syndrome, is a member of the RecQ DNA helicase family. BLM is phosphorylated by ATM and interacts with Rad51,
p53,and Top3, but its exact molecular function in the maintenance of genome stability remains largely unknown. Caenorhabditis elegans
him-6 (
e1104) mutants showing high incidence of males and partial embryonic lethality have a missense mutation in the
blm-1 gene. When the
him-6(
e1104) strain was irradiated with gamma-ray during germ cell development, embryonic lethality was significantly increased relative to the wild type strain, suggesting its critical function at the pachytene and mitotic germ stages. Even in the absence of gamma-irradiation, apoptosis was increased significantly in the germ cells of
him-6 strain and the increase was dependent on a
p53 homologue (Cep-1). In order to determine the relationships of
blm-1 with other genes involved in DNA recombination, repair, or replication,
mre-11,
cku-80,
dna-2 , and
rad-51 gene expression was inhibited by RNA interference in
him-6 mutants. Upon RNA i of
mre-11,
cku-80 , or
dna-2 , the embryonic hatching rate was further decreased in
him-6 strain relative to that in wild type. Thus, we conclude that these three genes have activities complementing
blm-1 . However, the embryonic hatching rate after
rad-51 RNA i was the same in both strains, suggesting that
blm-1 functions in the same pathway of homologus recombination as
rad-51 .