Processing and Visualization of Protec-Seq Data for the Generation of Calibrated, Genome-Wide Double Double-Strand Break (dDSB) Maps.

This chapter describes the computational pipeline for the processing and visualization of Protec-Seq data, a method for purification and genome-wide mapping of double-stranded DNA protected by a specific protein at both ends. In the published case, the protein of choice was Saccharomyces cerevisiae Spo11, a conserved topoisomerase-like enzyme that makes meiotic double-strand breaks (DSBs) to initiate homologous recombination, ensuring proper segregation of homologous chromosomes and fertility. The isolated DNA molecules were thus termed double DSB (dDSB) fragments and were found to represent 34 to several hundred base-pair long segments that are generated by Spo11 and are enriched at DSB hotspots, which are sites of topological stress.

Turning coldspots into hotspots: targeted recruitment of axis protein Hop1 stimulates meiotic recombination in Saccharomyces cerevisiae.

The DNA double-strand breaks that initiate meiotic recombination are formed in the context of the meiotic chromosome axis, which in Saccharomyces cerevisiae contains a meiosis-specific cohesin isoform and the meiosis-specific proteins Hop1 and Red1. Hop1 and Red1 are important for double-strand break formation; double-strand break levels are reduced in their absence and their levels, which vary along the lengths of chromosomes, are positively correlated with double-strand break levels. How axis protein levels influence double-strand break formation and recombination remains unclear.

Meiotic prophase roles of Rec8 in crossover recombination and chromosome structure.

Rec8 is a prominent component of the meiotic prophase chromosome axis that mediates sister chromatid cohesion, homologous recombination and chromosome synapsis. Here, we explore the prophase roles of Rec8. (i) During the meiotic divisions, Rec8 phosphorylation mediates its separase-mediated cleavage.

Smc5/6-Mms21 prevents and eliminates inappropriate recombination intermediates in meiosis.

Repairing broken chromosomes via joint molecule (JM) intermediates is hazardous and therefore strictly controlled in most organisms. Also in budding yeast meiosis, where production of enough crossovers via JMs is imperative, only a subset of DNA breaks are repaired via JMs, closely regulated by the ZMM pathway. The other breaks are repaired to non-crossovers, avoiding JM formation, through pathways that require the BLM/Sgs1 helicase.

Ubc9 sumoylation controls SUMO chain formation and meiotic synapsis in Saccharomyces cerevisiae.

Posttranslational modification with the small ubiquitin-related modifier SUMO depends on the sequential activities of E1, E2, and E3 enzymes. While regulation by E3 ligases and SUMO proteases is well understood, current knowledge of E2 regulation is very limited. Here, we describe modification of the budding yeast E2 enzyme Ubc9 by sumoylation (Ubc9(*)SUMO).

Separation of roles of Zip1 in meiosis revealed in heterozygous mutants of Saccharomyces cerevisiae.

Synapsis of homologs during meiotic prophase I is associated with a protein complex built along the bivalents--the synaptonemal complex (SC). Mutations in the SC-component gene ZIP1 diminish SC formation, leading to reduced recombination levels and low spore viability. Here we show that in SK1 strains heterozygous for a deletion of ZIP1 in certain regions meiotic interference are impaired with no decrease in recombination levels.