Caenorhabditis elegans lin-13, a member of the LIN-35 Rb class of genes involved in vulval development, encodes a protein with zinc fingers and an LXCXE motif

The SynMuv genes appear to be involved in providing a signal that inhibits vulval precursor cells from adopting vulval fates in Caenorhabditis elegans . One group of SynMuv genes, termed class B, includes genes encoding protei ns related to the tumor suppressor Rb and RbAp48, a protein that binds Rb. Here, we provide genetic evidence that lin-13 behaves as a class B SynMuv g ene. We show that null alleles of lin-13 are temperature sensitive and mate rnally rescued, resulting in phenotypes ranging in severity from L2 arrest (when both maternal and zygotic activities are removed at 25 degrees), to s terile Multivulva (when only zygotic activity is removed at 25 degrees), to sterile non-Multivulva (when both maternal and zygotic activities are remo ved at 15 degrees), to wild-type/class B SynMuv (when only zygotic activity is removed at 15 degrees). We also show that LIN-13 is a nuclear protein t hat contains multiple zinc fingers and a motif, LXCXE, that has been implic ated in Rb binding. These results together suggest a role for LIN-13 in Rb- mediated repression of vulval fates.