Project description:In many organisms, meiotic chromosomes are bundled at their telomeres to form a bouquet arrangement. The bouquet formation plays an important role in homologous chromosome pairing and therefore progression of meiosis. As meiotic telomere clustering occurs in response to mating pheromone signaling in fission yeast, we looked for factors essential for bouquet formation among genes induced under mating pheromone signaling. This genome-wide search identified two novel proteins, Bqt1 and Bqt2, that connect telomeres to the spindle-pole body (SPB; the centrosome equivalent in fungi). Neither Bqt1 nor Bqt2 alone functions as a connector, but together the two proteins form a bridge between Rap1 (a telomere protein) and Sad1 (an SPB protein). Significantly, when both Bqt1 and Bqt2 are ectopically expressed in mitotic cells, they also form a bridge between Rap1 and Sad1. Thus, a complex including Bqt1 and Bqt2 is essential for connecting telomeres to the SPB. Keywords: Keywards: Time course, Nitrogen starvation, Mating pheromone, P-factor.
Project description:Meiotic recombination facilitates accurate pairing and faithful segregation of homologous chromosomes by forming physical connections (crossovers) between homologs. Developmentally programmed DNA double-strand breaks (DSBs) generated by Spo11 protein (Rec12 in fission yeast) initiate meiotic recombination. Until recently, attempts to address the basis of the highly non-random distribution of DSBs on a genome-wide scale have been limited to 0.1–1 kb resolution of DSB position. We have assessed individual DSB events across the Schizosaccharomyces pombe genome at near-nucleotide resolution by deep-sequencing the short oligonucleotides connected to Rec12 following DNA cleavage. The single oligonucleotide size-class generated by Rec12 allowed us to effectively analyze all break events. Our high-resolution DSB map shows that the influence of underlying nucleotide sequence and chromosomal architecture differs in multiple ways from that in budding yeast. Rec12 action is not strongly restricted to nucleosome-depleted regions but is nevertheless spatially biased with respect to chromatin structure. Furthermore, we find strong evidence across the genome for differential DSB repair previously predicted to account for crossover invariance (constant cM/kb in spite of DSB hotspots). Our genome-wide analyses demonstrate evolutionarily fluid factors contributing to crossover initiation and its regulation.
Project description:In most eukaryotes, the meiotic chromosomal bouquet (comprising clustered chromosome ends) provides an ordered chromosome arrangement that facilitates pairing and recombination between homologous chromosomes. In the protist Tetrahymena thermophila, the meiotic prophase nucleus stretches enormously and chromosomes assume a bouquet-like arrangement in which telomeres and centromeres are attached to opposite poles of the nucleus. We have identified and characterized three meiosis-specific genes (MELG1-3) that control nuclear elongation and centromere and telomere clustering. Hence, to find out potential interactions, we did LC-MS/MS analysis for Melg1, Melg2, Melg3, and Tass1 (a partner of Melg3) immunoprecipitation samples.
Project description:We used CLIP-Seq to determine the RNAs bound specifically to RNA binding protein Mei2 in early meiosis in fission yeast. We added a TAP tag to the C-terminal ends of two meiotic RNA binding proteins, Mei2 and Msa1. We used an untagged fission yeast strain as a negative control. These strains were nitrogen starved and allowed to progress into meiosis, after which they were harvested, lyzed and crosslinking immunoprecipitaion was performed. The RNAs purified after CLIP were sequenced