Project description:Splicing regulatory networks are essential components of eukaryotic gene expression programs, yet little is known about how they are integrated with transcriptional regulatory networks into coherent gene expression programs. Here we define the MER1 splicing regulatory network and examine its role in the gene expression program during meiosis in budding yeast. Mer1p splicing factor promotes splicing of just four pre-mRNAs. All four Mer1p-responsive genes also require Nam8p for splicing activation by Mer1p, however other genes require Nam8p but not Mer1p, exposing an overlapping meiotic splicing network controlled by Nam8p. MER1 mRNA and three of the four Mer1p substrate pre-mRNAs are induced by the transcriptional regulator Ume6p. This unusual arrangement delays expression of Mer1p-responsive genes relative to other genes under Ume6p control. Products of Mer1p-responsive genes are required for initiating and completing recombination, and for activation of Ndt80p, the transcriptional network that controls subsequent steps in the program. Thus the MER1 splicing regulatory network mediates the dependent relationship between the UME6 and NDT80 transcriptional regulatory networks in the meiotic gene expression program. This work reveals how splicing regulatory networks can be interlaced with transcriptional regulatory networks in eukaryotic gene expression programs. This SuperSeries is composed of the SubSeries listed below.
Project description:Despite its streamlined genome, there are important examples of regulated RNA splicing in Saccharomyces cerevisiae. One of the most striking is the regulated splicing of meiotic transcripts, part of the dramatic reprogramming of gene expression upon meiotic onset. Here we show a crucial role for the chromatin remodeler Snf2, part of the Swi/Snf complex in meiotic regulation of splicing. We find that the complex affects meiotic splicing in several ways. First, meiosis-specific expression of the splicing activator Mer1 is Swi/Snf dependent, involves precise timing of acetylation of histone H3K9 at the MER1 locus, and changes in the acetylation state of Snf2. Additionally, Swi/Snf abundance regulates meiosis-specific downregulation of ribosomal protein encoding RNAs, leading to the redistribution of spliceosomes from this abundant class of intron-containing RNAs to meiotic transcripts. This regulation is achieved by rapid downregulation of the Snf2 protein. Taken together these data reveal that the Swi/Snf complex coordinates a cascade of events to direct the regulated splicing of meiotic genes, establishing it as a master regulator of meiotic splicing in S. cerevisiae.
Project description:Here we studied the budding yeast Lachancea kluyveri, a cousin of the model Saccharomyces cerevisiae, in order to try to understand the mechanism responsible for the absence of meiotic recombination on its almost entire sex chromosome (Brion et al. 2017). We performed meiotic DSB mapping using CC-seq (Gittens 2019). Briefly, we observed a distribution of meiotic DSBs mainly in gene promoters as in S. cerevisiae and a depletion within Lakl0C-left (the 1 Mb long domain on the sex chromosome with no meiotic recombination). Also, we noted a poor conservation of DSB hotspots strength between L. kluyveri and S. cerevisiae.
Project description:To investigate the relationship between chromatin organization and meiotic processes, we used Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE) to map open chromatin during the transition from mitosis to meiosis in the budding yeast Saccharomyces cerevisiae.
Project description:To better understand the gene regulatory mechanisms that program developmental processes, we carried out simultaneous, genome-wide measurements of mRNA, translation and protein through meiotic differentiation in budding yeast.
Project description:Ray2013 - Meiotic initiation in S. cerevisiae
A mathematical representation of early meiotic events, particularly feedback mechanisms at the system level and phosphorylation of signalling molecules for regulating protein activities, is described here
This model is described in the article:
Dynamic modeling of yeast meiotic initiation.
Ray D, Su Y, Ye P.
BMC Syst Biol. 2013 May 1;7:37
Abstract:
BACKGROUND:
Meiosis is the sexual reproduction process common to eukaryotes. The diploid yeast Saccharomyces cerevisiae undergoes meiosis in sporulation medium to form four haploid spores. Initiation of the process is tightly controlled by intricate networks of positive and negative feedback loops. Intriguingly, expression of early meiotic proteins occurs within a narrow time window. Further, sporulation efficiency is strikingly different for yeast strains with distinct mutations or genetic backgrounds. To investigate signal transduction pathways that regulate transient protein expression and sporulation efficiency, we develop a mathematical model using ordinary differential equations. The model describes early meiotic events, particularly feedback mechanisms at the system level and phosphorylation of signaling molecules for regulating protein activities.
RESULTS:
The mathematical model is capable of simulating the orderly and transient dynamics of meiotic proteins including Ime1, the master regulator of meiotic initiation, and Ime2, a kinase encoded by an early gene. The model is validated by quantitative sporulation phenotypes of single-gene knockouts. Thus, we can use the model to make novel predictions on the cooperation between proteins in the signaling pathway. Virtual perturbations on feedback loops suggest that both positive and negative feedback loops are required to terminate expression of early meiotic proteins. Bifurcation analyses on feedback loops indicate that multiple feedback loops are coordinated to modulate sporulation efficiency. In particular, positive auto-regulation of Ime2 produces a bistable system with a normal meiotic state and a more efficient meiotic state.
CONCLUSIONS:
By systematically scanning through feedback loops in the mathematical model, we demonstrate that, in yeast, the decisions to terminate protein expression and to sporulate at different efficiencies stem from feedback signals toward the master regulator Ime1 and the early meiotic protein Ime2. We argue that the architecture of meiotic initiation pathway generates a robust mechanism that assures a rapid and complete transition into meiosis. This type of systems-level regulation is a commonly used mechanism controlling developmental programs in yeast and other organisms. Our mathematical model uncovers key regulations that can be manipulated to enhance sporulation efficiency, an important first step in the development of new strategies for producing gametes with high quality and quantity.
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Project description:The Spo11-generated double-strand breaks (DSBs) that initiate meiotic recombination are non-randomly distributed across the genome. Here, we use S1Seq mapping to map the distribution of meiotic DSBs in spo11 mutant strains of Saccharomyces cerevisiae.
Project description:The Spo11-generated double-strand breaks (DSBs) that initiate meiotic recombination are non-randomly distributed across the genome. Here, we use Spo11-oligonucleotide complexes to map the distribution of meiotic DSBs in a spo11 mutant strain of Saccharomyces cerevisiae.
Project description:The Spo11-generated double-strand breaks (DSBs) that initiate meiotic recombination are non-randomly distributed across the genome. Here, we use Spo11-oligonucleotide complexes, a byproduct of DSB formation, to map the distribution of meiotic DSBs in pch2 and sir2 mutant strains of Saccharomyces cerevisiae.
Project description:We used ChIP-seq to determine the whole-genome enrichment of histone H3 threonine 11 phosphorylation (H3 T11ph) during Saccharomyces cerevisiae meiosis. S. cerevisiae SK1 cells were synchronized for meiotic entry and 3 and 4 hour meiotic samples were obtained. As H3 T11ph is dependent on the formation of meiotic double strand breaks (DSBs), a negative control ChIP-seq sample was obtained from a strain lacking DSBs (spo11-yf). Concurrently, ChIP-seq was carried out for histone H3 as a control for comparision.