ZIP2, A MEIOSIS-SPECIFIC PROTEIN REQUIRED FOR THE INITIATION OF CHROMOSOME SYNAPSIS

We describe the identification and characterization of the Saccharomyc es cerevisiae ZIP2 gene, which encodes a novel meiosis-specific protei n essential for synaptonemal complex formation. In the zip2 mutant, ch romosomes are homologously paired but not synapsed. The Zip2 protein l ocalizes to discrete foci on meiotic chromosomes; these foci correspon d to sites of convergence between paired homologs that are believed to be sites of synapsis initiation. Localization of Zip2p requires the i nitiation of meiotic recombination. In a mutant defective in double-st rand break repair, Zip2p colocalizes with proteins involved in double- strand break formation and processing. We propose that Zip2p promotes the initiation of chromosome synapsis and that localization of Zip2p t o sites of interhomolog recombination ensures synapsis between homolog ous chromosomes.