Limits...
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 position changes in response to transcription.(A) Gene expression of the GAL2/SRL2 convergent gene pair in response to different concentrations of copper was measured by RT-qPCR at the indicated time points. Copper was added to the sporulation medium at 2 hr, and samples were collected at 2 hr and 3 hr. Transcription levels of both convergent genes were examined in a wild-type strain and a strain harboring a pCUP1 promoter insertion upstream of GAL2. Error bars: S.D. of three independent replicates. (B) ChIP-qPCR analysis of Red1 binding from the same experiment as in (A). Schematic depicts relative positions of primer pairs. Error bars: S.D.DOI:http://dx.doi.org/10.7554/eLife.07424.007
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4530585&req=5

fig3s1: Red1 position changes in response to transcription.(A) Gene expression of the GAL2/SRL2 convergent gene pair in response to different concentrations of copper was measured by RT-qPCR at the indicated time points. Copper was added to the sporulation medium at 2 hr, and samples were collected at 2 hr and 3 hr. Transcription levels of both convergent genes were examined in a wild-type strain and a strain harboring a pCUP1 promoter insertion upstream of GAL2. Error bars: S.D. of three independent replicates. (B) ChIP-qPCR analysis of Red1 binding from the same experiment as in (A). Schematic depicts relative positions of primer pairs. Error bars: S.D.DOI:http://dx.doi.org/10.7554/eLife.07424.007

Mentions: To further test this possibility, we examined whether changing the level of gene expression is sufficient to alter Red1 binding patterns at axis association sites. We utilized the copper-inducible CUP1 promoter (pCUP1) to drive the expressions of two genes: GCY1 and GAL2. Both genes exhibit low transcriptional activities during early stages of sporulation and are located in convergent gene pairs, in which the convergently transcribed neighbor is more highly expressed. Two concentrations of copper (5 μM and 20 μM) were applied to induce different levels of expression during early meiosis. In wild-type control cells, the Red1 binding profile was skewed to the sides of the weakly transcribed GCY1 and GAL2 genes irrespective of copper concentrations (Figure 3C,D shows GCY1; see Figure 3—figure supplement 1A,B for GAL2). A similar profile was also observed for the pCUP1 strains in the absence of copper, although a shift of Red1 binding away from pCUP1 was apparent and correlated well with the leaky expression of this promoter (compare Figure 3C,D; also Figure 3—figure supplement 1A,B). Addition of 5 μM Cu2+ induced a marked shift in the Red1 binding pattern toward the downstream gene. This shift was further exacerbated upon addition of 20 μM Cu2+ (Figure 3D and Figure 3—figure supplement 1B), indicating that the transcription levels of convergent genes underlie the dynamic binding patterns of axis proteins. Such refocusing could either result from sliding motion or repeated recruitment to a chromatin modification or structure at the 3′ ends of transcription bubbles. Previous studies have shown that cohesin is able to change position in response to transcription (Glynn et al., 2004; Lengronne et al., 2004; Bausch et al., 2007). Thus, association with cohesin may explain the transcriptional effects we observe for axis proteins.


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 position changes in response to transcription.(A) Gene expression of the GAL2/SRL2 convergent gene pair in response to different concentrations of copper was measured by RT-qPCR at the indicated time points. Copper was added to the sporulation medium at 2 hr, and samples were collected at 2 hr and 3 hr. Transcription levels of both convergent genes were examined in a wild-type strain and a strain harboring a pCUP1 promoter insertion upstream of GAL2. Error bars: S.D. of three independent replicates. (B) ChIP-qPCR analysis of Red1 binding from the same experiment as in (A). Schematic depicts relative positions of primer pairs. Error bars: S.D.DOI:http://dx.doi.org/10.7554/eLife.07424.007
© Copyright Policy
Related In: Results  -  Collection

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

fig3s1: Red1 position changes in response to transcription.(A) Gene expression of the GAL2/SRL2 convergent gene pair in response to different concentrations of copper was measured by RT-qPCR at the indicated time points. Copper was added to the sporulation medium at 2 hr, and samples were collected at 2 hr and 3 hr. Transcription levels of both convergent genes were examined in a wild-type strain and a strain harboring a pCUP1 promoter insertion upstream of GAL2. Error bars: S.D. of three independent replicates. (B) ChIP-qPCR analysis of Red1 binding from the same experiment as in (A). Schematic depicts relative positions of primer pairs. Error bars: S.D.DOI:http://dx.doi.org/10.7554/eLife.07424.007
Mentions: To further test this possibility, we examined whether changing the level of gene expression is sufficient to alter Red1 binding patterns at axis association sites. We utilized the copper-inducible CUP1 promoter (pCUP1) to drive the expressions of two genes: GCY1 and GAL2. Both genes exhibit low transcriptional activities during early stages of sporulation and are located in convergent gene pairs, in which the convergently transcribed neighbor is more highly expressed. Two concentrations of copper (5 μM and 20 μM) were applied to induce different levels of expression during early meiosis. In wild-type control cells, the Red1 binding profile was skewed to the sides of the weakly transcribed GCY1 and GAL2 genes irrespective of copper concentrations (Figure 3C,D shows GCY1; see Figure 3—figure supplement 1A,B for GAL2). A similar profile was also observed for the pCUP1 strains in the absence of copper, although a shift of Red1 binding away from pCUP1 was apparent and correlated well with the leaky expression of this promoter (compare Figure 3C,D; also Figure 3—figure supplement 1A,B). Addition of 5 μM Cu2+ induced a marked shift in the Red1 binding pattern toward the downstream gene. This shift was further exacerbated upon addition of 20 μM Cu2+ (Figure 3D and Figure 3—figure supplement 1B), indicating that the transcription levels of convergent genes underlie the dynamic binding patterns of axis proteins. Such refocusing could either result from sliding motion or repeated recruitment to a chromatin modification or structure at the 3′ ends of transcription bubbles. Previous studies have shown that cohesin is able to change position in response to transcription (Glynn et al., 2004; Lengronne et al., 2004; Bausch et al., 2007). Thus, association with cohesin may explain the transcriptional effects we observe for axis proteins.

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