Accurate chromosome segregation requires separation of the sister chromatids during the metaphase-to-anaphase transition. This is achieved when the anaphase-promoting complex (APC/cyclosome) brings about the destruction of securin, an inhibitor of the cysteine protease known as separase. Once activated, separase can then cleave the SCC-1 protein, a member of the cohesion complex that holds the sister chromatids together.In C. elegans, the
sep-1(
e2406) temperature-sensitive mutant allele of separase causes a pleiotropic phenotype when worms are grown at 20C (Siomos et al, 2001). In addition to complete sterility and embryonic lethality,
sep-1(
e2406) also causes developmental abnormalities in the germ line, somatic gonad, and the vulva. We have recently isolated new temperature sensitive alleles of
sep-1 (
ax110 and
ax521) and are currently characterizing their respective phenotypes.In an effort to identify novel regulators and substrates of separase, we have performed a suppressor screen to select for mutations that can rescue the sterility and embryonic lethality associated with the
sep-1(
e2406) allele when grown at the restrictive temperature. Mutant alleles representing three different loci were recovered and we are currently mapping their position using molecular and classical genetic techniques. We are investigating the ability of these suppressor alleles to modulate the new
sep-1 mutant phenotypes. We are also determining the phenotype of these suppressor mutants alone, and whether they act in a similar process by constructing double mutants.