Screens for suppressors of
cul-2 and
zyg-11 P> P> PERSONNAME> GIVENNAME> Srividya GIVENNAME> SN> PERSONNAME> Vasudevan PERSONNAME> SN> PERSONNAME> , PERSONNAME> GIVENNAME> Edward GIVENNAME> SN> Kipreos SN> PERSONNAME> Dept. of Cellular Biology PLACE> PLACETYPE> University PLACETYPE> of PLACENAME> Georgia PLACENAME> PLACE> , PLACE> CITY> Athens CITY> , STATE> GA STATE> POSTALCODE> 30602 POSTALCODE> PLACE> P> P> CUL-2 is a member of the cullin E3 ubiquitin-ligase family. In humans, CUL-2 is present in a protein complex with PERSONNAME> GIVENNAME> Elongin GIVENNAME> SN> B SN> PERSONNAME> , PERSONNAME> GIVENNAME> Elongin GIVENNAME> SN> C SN> PERSONNAME> , RBX1, and the tumor suppressor protein VHL, which targets the hypoxia inducible factor, HIF-1 a for degradation ( Lonergan et al. Mol. Cell. Biol., 1998). In C.elegans loss of the
cul-2 gene causes a G1 phase germ cell arrest associated with an accumulation of the CDK inhibitor CKI-1. Inactivation of CUL-2 also causes a host of embryonic phenotypes such as failure to extrude the second polar body, cytoplasmic extensions, DNA bridges, multinuclei , and arrest at the 24-cell stage (Feng et al. Nat. Cell Biol., 1999). P> P> In fertilized
cul-2 mutant zygotes, meiotic anaphase I occurs normally, but anaphase II is abolished or severely delayed. The meiotic delay is associated with the stabilization of cyclin B1, which is normally degraded during meiosis I and II in wild type. The extended meiosis II is also correlated with reversals in several aspects of AP polarity ( PERSONNAME> GIVENNAME> Ji GIVENNAME> SN> Liu SN> PERSONNAME> , GIVENNAME> S.V. GIVENNAME> , and E.T.K., Development, in press). P> P> Interestingly, inactivation of the leucine -rich repeat protein ZYG-11 produces a broad overlap with the
cul-2 mutant phenotypes ( Kemphues et al. Dev Biol , 1986).
zyg-11 mutants do not have a germ cell arrest, but they do share meiotic and embryonic defects with
cul-2 mutants, including stabilization of cyclin B1 and polarity reversals. Combining null alleles of
cul-2 and
zyg-11 does not enhance the meiotic delay observed for each mutant individually suggesting that the two genes function in the same pathway ( PERSONNAME> GIVENNAME> Ji GIVENNAME> SN> Liu SN> PERSONNAME> , GIVENNAME> S.V. GIVENNAME> , and E.T.K., Development, in press). We are interested in elucidating the molecular pathways by which CUL-2 and ZYG-11 regulate meiosis and embryonic development. We are in the process of screening for CUL-2 and ZYG-11 genetic interactors using suppressor screens for
cul-2 and
zyg-11 mutants. The
cul-2 suppressor screen employs a
cul-2(
ek4) allele linked to
unc-64 to clonally screen F2 progeny for embryos that have progressed beyond the 24-cell stage. The
zyg-11 suppressor screen employs a ts allele of
zyg-11 to obtain viable suppressors. So far we have screened 20,000 F2 genomes and obtained a single suppressor of
zyg-11. We anticipate that these screens will provide information crucial to the understanding of how CUL-2 ubiquitin ligase activity regulates meiosis and embryonic development in C. elegans .