Transcription Dynamically Patterns the Meiotic Chromosome-Axis Interface [ChIP-Seq]

Meiotic chromosomes are highly compacted yet remain transcriptionally active. To understand how chromosome folding accommodates transcription, we investigated the assembly of the axial element, the proteinaceous structure that compacts meiotic chromosomes and promotes recombination and fertility. We found that the axial-element proteins of budding yeast are flexibly anchored to chromatin by the ring-like cohesin complex and biased towards small chromosomes by a separate modulating mechanism that requires the conserved axial element component Hop1. The ubiquitous presence of cohesin at sites of convergent transcription provides well-dispersed points for axis attachment and thus compaction. Axis protein enrichment at these sites directly correlates with the propensity for recombination initiation nearby. Importantly, axis anchoring by cohesin is adjustable and readily displaced in the direction of transcription by the transcriptional machinery. We propose that such robust but flexible tethering allows the highly structured axial element to promote recombination while easily adapting to changes in chromosome activity. Overall design: ChIP-seq experiments were undertaken to understand the features of meiotic chromosomal axes assembly in meiosis. The genome-wide distribution of axis proteins including Hop1, Red1 as well as cohesin subunits Rec8 and Smc3 were measured. Axis protein binding pattern is also measured in rec8 mutant and pREC8-SCC1 in rec8 mutant.