PAR-2, A GENE REQUIRED FOR BLASTOMERE ASYMMETRY IN CAENORHABDITIS-ELGANS, ENCODES ZINC-FINGER AND ATP-BINDING MOTIFS

The par-2 gene of Caenorhabditis elegans functions in early embryogene sis to ensure an asymmetric first cleavage and the segregation of cyto plasmic factors. Both processes appear to be required to generate daug hter blastomeres with distinct developmental potential. We isolated an allele of par-2 by using a screen for maternal-effect lethal mutation s in a strain known for its high frequency of transposition events. A transposable element was found to be linked to this allele. Sequences Ranking the site of transposon insertion were cloned and found to resc ue the par-2 mutant phenotype. DNA in the par-2 region hybridized to a 2.3-kb germ-line-enriched mRNA. The cDNA corresponding to this germ-l ine-enriched message was cloned, sequenced, and used to identify the m olecular lesions associated with three par-2 alleles. Sequence analysi s of the par-2 cDNA revealed that the predicted protein contained two distinct moths found in other known proteins: an ATP-binding site and a cysteine-rich motif which identifies the par-2 gene product as a mem ber of a growing class of putative zinc-binding proteins.