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Transcription dynamically patterns the meiotic chromosome-axis interface.

Sun X, Huang L, Markowitz TE, Blitzblau HG, Chen D, Klein F, Hochwagen A - Elife (2015)

Bottom Line: We found that the axial element proteins of budding yeast are flexibly anchored to chromatin by the ring-like cohesin complex.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 axial element to promote recombination while easily adapting to changes in chromosome activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, New York University, New York, United States.

ABSTRACT
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. The ubiquitous presence of cohesin at sites of convergent transcription provides well-dispersed points for axis attachment and thus chromosome compaction. Axis protein enrichment at these sites directly correlates with the propensity for recombination initiation nearby. A separate modulating mechanism that requires the conserved axial-element component Hop1 biases axis protein binding towards small chromosomes. 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 axial element to promote recombination while easily adapting to changes in chromosome activity.

No MeSH data available.


Related in: MedlinePlus

Red1 binding in rec8Δ mutants.(A) Distribution of widths of Red1 peaks in WT (green) and rec8Δ mutants (blue). (B) Probability of GAN motif occurrence around Red1 peak summits in WT (green) and rec8Δ mutants (blue). (C) Examples of correlation of Red1 binding and coding density along chromosomes III and X. Red1 signals were plotted unsmoothed. Coding density was calculated as in Figure 4E but using a smoothing window of 2 kb.DOI:http://dx.doi.org/10.7554/eLife.07424.009
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fig4s1: Red1 binding in rec8Δ mutants.(A) Distribution of widths of Red1 peaks in WT (green) and rec8Δ mutants (blue). (B) Probability of GAN motif occurrence around Red1 peak summits in WT (green) and rec8Δ mutants (blue). (C) Examples of correlation of Red1 binding and coding density along chromosomes III and X. Red1 signals were plotted unsmoothed. Coding density was calculated as in Figure 4E but using a smoothing window of 2 kb.DOI:http://dx.doi.org/10.7554/eLife.07424.009

Mentions: If cohesin plays a role in the transcription-dependent localization of meiotic axis proteins, these distribution patterns should no longer be apparent when the cohesin ring is disrupted. Our previous analysis had shown that in the absence of meiotic cohesin Rec8, Hop1 still associates with chromosomes but displays large regions of depletion alternating with dense clusters of binding (Panizza et al., 2011), a pattern that was also mirrored by Red1 (Figure 4A). These large-scale changes in rec8Δ mutants were associated with markedly narrower Red1 peaks (Figure 4—figure supplement 1A). Importantly, Red1 was no longer biased to the 3′ ends of genes (Figure 4B) and focusing of axis proteins at convergent regions was strongly reduced (Figure 4C), implying that transcriptional focusing of axis proteins depends on cohesin. By contrast, the small-chromosome bias of axis protein binding persisted in rec8Δ mutants (Figure 4D), indicating that Red1 is enriched on small chromosomes independently of Rec8.10.7554/eLife.07424.008Figure 4.Transcriptional focusing depends on cohesin.


Transcription dynamically patterns the meiotic chromosome-axis interface.

Sun X, Huang L, Markowitz TE, Blitzblau HG, Chen D, Klein F, Hochwagen A - Elife (2015)

Red1 binding in rec8Δ mutants.(A) Distribution of widths of Red1 peaks in WT (green) and rec8Δ mutants (blue). (B) Probability of GAN motif occurrence around Red1 peak summits in WT (green) and rec8Δ mutants (blue). (C) Examples of correlation of Red1 binding and coding density along chromosomes III and X. Red1 signals were plotted unsmoothed. Coding density was calculated as in Figure 4E but using a smoothing window of 2 kb.DOI:http://dx.doi.org/10.7554/eLife.07424.009
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4530585&req=5

fig4s1: Red1 binding in rec8Δ mutants.(A) Distribution of widths of Red1 peaks in WT (green) and rec8Δ mutants (blue). (B) Probability of GAN motif occurrence around Red1 peak summits in WT (green) and rec8Δ mutants (blue). (C) Examples of correlation of Red1 binding and coding density along chromosomes III and X. Red1 signals were plotted unsmoothed. Coding density was calculated as in Figure 4E but using a smoothing window of 2 kb.DOI:http://dx.doi.org/10.7554/eLife.07424.009
Mentions: If cohesin plays a role in the transcription-dependent localization of meiotic axis proteins, these distribution patterns should no longer be apparent when the cohesin ring is disrupted. Our previous analysis had shown that in the absence of meiotic cohesin Rec8, Hop1 still associates with chromosomes but displays large regions of depletion alternating with dense clusters of binding (Panizza et al., 2011), a pattern that was also mirrored by Red1 (Figure 4A). These large-scale changes in rec8Δ mutants were associated with markedly narrower Red1 peaks (Figure 4—figure supplement 1A). Importantly, Red1 was no longer biased to the 3′ ends of genes (Figure 4B) and focusing of axis proteins at convergent regions was strongly reduced (Figure 4C), implying that transcriptional focusing of axis proteins depends on cohesin. By contrast, the small-chromosome bias of axis protein binding persisted in rec8Δ mutants (Figure 4D), indicating that Red1 is enriched on small chromosomes independently of Rec8.10.7554/eLife.07424.008Figure 4.Transcriptional focusing depends on cohesin.

Bottom Line: We found that the axial element proteins of budding yeast are flexibly anchored to chromatin by the ring-like cohesin complex.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 axial element to promote recombination while easily adapting to changes in chromosome activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, New York University, New York, United States.

ABSTRACT
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. The ubiquitous presence of cohesin at sites of convergent transcription provides well-dispersed points for axis attachment and thus chromosome compaction. Axis protein enrichment at these sites directly correlates with the propensity for recombination initiation nearby. A separate modulating mechanism that requires the conserved axial-element component Hop1 biases axis protein binding towards small chromosomes. 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 axial element to promote recombination while easily adapting to changes in chromosome activity.

No MeSH data available.


Related in: MedlinePlus