G Roeder

..Together, these results suggest that two Zip1 dimers, lying head-to-head, span the width of the SC...

..Progress has been made in identifying components of the cell-cycle machinery that are impacted by the checkpoint...

..We propose that the Bdf1 protein is a component of chromatin and that the mitotic and meiotic defects of the bdf1 null mutant result from alterations in chromatin structure...

..Under certain circumstances, Sir3-dependent localization of Pch2 to telomeres also provides checkpoint function. These unexpected findings link the nucleolus, chromatin silencing, and the pachytene checkpoint...

..We speculate that Zip3 is a component of recombination nodules and serves to link the initiation of synapsis to meiotic recombination...

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..We speculate that phosphorylated Red1 prevents exit from pachytene and that completion of meiotic recombination triggers Glc7-dependent dephosphorylation of Red1...

..We propose that Zip2p promotes the initiation of chromosome synapsis and that localization of Zip2p to sites of interhomolog recombination ensures synapsis between homologous chromosomes...

..We propose that the Hop2 protein functions to prevent synapsis between nonhomologous chromosomes...

..The REC102 gene was cloned based on complementation of the mutant defect and the gene was mapped to chromosome XII between CDC25 and STE11...

..In a zip1 haploid, axial associations are not apparent, suggesting that these associations depend on interactions between homologous sequences...

..Fluorescent in situ hybridization analysis indicates that Mek1-mediated phosphorylation of Red1 is required for meiotic sister-chromatid cohesion, raising the possibility that cohesion is regulated by protein phosphorylation...

..The sequence of the MEK1 gene predicts a 56.8-kD protein with homology to serine-threonine protein kinases. The MEK1 gene maps to chromosome XV, 13 cM proximal to CDC64. Models for the function of the MEK1 gene product are proposed...

..We discuss here possibilities for how a telomere-associated protein might function in chromosome synapsis and crossover interference...

..Our results indicate that inhibition of Ndt80 activity is one mechanism used to achieve pachytene arrest...

..The requirement for Swe1 distinguishes the pachytene checkpoint from the DNA damage checkpoints operating in vegetative cells...

..We suggest that the primary defect in the mer2 mutant is in the initiation of meiotic genetic exchange...

..One interpretation of this result is that only those crossovers that occur in the context of the synaptonemal complex lead to the establishment of functional chiasmata. The MER2 gene product is essential for meiosis...

..5 kilodaltons. There is no significant homology between the RED1 amino acid sequence and other known protein sequences, including those encoded by genes essential for meiosis...

..Strains carrying disruptions of the MER1 gene are mitotically viable. The epistatic relationships between MER1 and previously characterized meiotic genes are described...

..The mei4 mutation is able to rescue the spore-inviability phenotype of spo13 and 52 strains (i.e., mei4 spo13 rad52 mutants produce viable spores), indicating that MEI4 acts before RAD52 in the meiotic recombination pathway...

..In vegetative cells, mutation of DOT1 results in delocalization of Sir3 from telomeres, accounting for the impaired telomeric silencing in dot1...

..Cytological analysis of mei4 mutant strains during meiotic prophase demonstrates that the chromosomes form long axial elements that fail to undergo synapsis. The meiosis II division is delayed in mei4 strains...

..In contrast, the role of Zip1p in synapsis is separable from its role in meiotic cell cycle progression. zip1 mutants display interval-specific effects on crossing over...

..Therefore, at least one of the functions of the MER1 protein is to mediate splicing of the MER2 transcript. Genetic data suggest that the MER1 gene may also be responsible for splicing the transcript of at least one other gene...

..Both Zip2 and Zip1 are required for the normal localization of Msh4 to chromosomes, raising the possibility that the zip1 and zip2 defects in crossing over are indirect, resulting from the failure to localize Msh4 properly...

..RNase T1 footprinting indicates that the Mer1 protein contacts MER2 RNA at several points in the 5' exon and in the intron. Thus, Mer1 interacts directly with a regulatory element in MER2 RNA and promotes splicing...

..Our results will allow researchers who identify a yeast gene to determine immediately whether that gene is expressed at a specific time during the life cycle and whether its gene product localizes to a specific subcellular location...

..When this nucleotide is mutated to restore the consensus, base pairing with U1 snRNA is increased and the requirement for MER1 is alleviated...

..We demonstrate these features of the transposons by mutagenesis of the SPA2, ARP100, SER1, and BDF1 genes...

..These observations are consistent with previous genetic studies suggesting that Red1 and Hop1 directly interact. There is little or no Hop1 protein on pachytene chromosomes or in synapsed chromosomal regions...

..Our results demonstrate that Zip1 is a structural component of the central region of the SC. More specifically, we speculate that Zip1 is a component of the transverse filaments that lie perpendicular to the long axis of the complex...

..We propose that the RED1 gene product is involved in meiosis I chromosome disjunction, perhaps by maintaining the connections between homologous chromosomes through metaphase I...

..Unlike the S. cerevisiae RED1 gene, the K. lactis RED1 contains an intron; the transcript of the K. lactis gene is efficiently spliced during meiosis in S. cerevisiae...

..We hypothesize that the Sep1 protein participates directly in meiotic recombination and that other strand exchange enzymes, acting in parallel recombination pathways, are able to substitute partially for the absence of the Sep1 protein...

..Some of the meiotic recombination genes will be cloned and sequenced; expression of the cloned genes will be examined through the construction and analysis of lacZ fusion genes...

..Activity of the Cdcl4 phosphatase is regulated by sequestration in the nucleolus. The possibility that Pch2 regulates Cdcl4 activity will be tested by examining the effects of Cdcl4 inactivation and overproduction. ..