Project description:During meiosis in yeast, global splicing efficiency increases. The mechanism for this is relief of competition for the splicing machinery by repression of intron-containing ribosomal protein genes (RPGs). Repression of RPGs with rapamycin also increases splicing efficiency in vegetative cells. Reducing levels of an RPG-dedicated transcription factor globally improves splicing and suppresses the temperature-sensitive growth defect of a spliceosome mutation. These results indicate that the spliceosome is limiting and pre-mRNAs compete with each other. Under these conditions, splicing efficiency of a given pre-mRNA therefore depends on both its concentration and affinity for the limiting splicing factor(s) as well as those of the competing pre-mRNAs. We propose that trans-competition control of splicing helps repress meiotic gene expression in vegetative cells, and promotes efficient meiosis. Competition between RNAs for a limiting factor may be a general condition important for function of a variety of post-transcriptional control mechanisms. Splicing and gene expression profiles of 1) wild type yeast cells treated with rapamycin (2 biological replicates) relative to untreated cells and 2) prp4-1 pGAL-IFH1 (down-regulated expression of IFH1 transcription factor(specific for ribosomal protein genes)) relative to prp4-1 yeast.
Project description:During meiosis in yeast, global splicing efficiency increases. The mechanism for this is relief of competition for the splicing machinery by repression of intron-containing ribosomal protein genes (RPGs). Repression of RPGs with rapamycin also increases splicing efficiency in vegetative cells. Reducing levels of an RPG-dedicated transcription factor globally improves splicing and suppresses the temperature-sensitive growth defect of a spliceosome mutation. These results indicate that the spliceosome is limiting and pre-mRNAs compete with each other. Under these conditions, splicing efficiency of a given pre-mRNA therefore depends on both its concentration and affinity for the limiting splicing factor(s) as well as those of the competing pre-mRNAs. We propose that trans-competition control of splicing helps repress meiotic gene expression in vegetative cells, and promotes efficient meiosis. Competition between RNAs for a limiting factor may be a general condition important for function of a variety of post-transcriptional control mechanisms.
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:Processing of Immunoglobulin heavy chain (IgH) mRNA is a paradigm for competition between splicing and polyadenylation. In plasma cells pre-mRNA is polyadenylated mainly at the promoter-proximal secretory site while B-cells utilize a cryptic 5â?? splice site in the last secretory-specific exon; these are mutually exclusive events for all IgH pre-mRNAs. Transcription elongation factor ELL2, more abundant in plasma cells relative to B-cells, was down-modulated by overexpression of heterogenous ribonucleoprotein F, a condition which reduced production of secretory IgH mRNA. Transfection of B-cells with ELL2 and the IgH reporter showed an accelerated use of the secretory poly(A) site, positioned in competition with the splice to M1; a small interfering RNA to ELL2 reduced expression of IgH secretory mRNA. Co-transcription factors ELL1 and PC4 were ineffective at driving secretory-poly(A) site use. ELL2 had little effect on poly(A) site choice with reporters containing tandem-linked poly(A) sites. Shorter forms of ELL2 protein result from both internal initiation at M186 and protein processing. An alternative splicing reporter driven by IgH or non-Ig promoters revealed that ELL2 and its M186 initiated form were able to accelerate exon skipping. Therefore, ELL2 influences IgH pre-mRNA processing through facilitating skipping of the alternative splice to the membrane form. Experiment Overall Design: AxJ plasma cells were stably transfected to overexpress hnRNP-F, -H or empty vector. Clones showing high overexpression levels of F or H by western blot were selected. The IgH sec to mb ratios of these clones were determined. A global gene expression analysis was performed on mRNA from two clones from hnRNP-F, which demonstrated a lower sec:mb ratio, and one from each of the controls: overexpression of hnRNP-H, or transfection with empty vector, or A20 B-cells, using Affymetrix gene micro array technology.
Project description:This project aims to identify novel RNA binding proteins in the baker's yeast, Saccharomyces cerevisiae. Since interactions between RNAs and proteins may be transient, yeast cells were crosslinked with UV light at 254 nm which promotes the covalent link between proteins and RNAs. After this, polyadenylated mRNAs were purified via oligo(dT) coupled to magentic beads under stringet conditions. Finally, samples were subjected to mass spectrometry analysis. To rule out the possibility of RNA-independent binding we also analysed other samples: i) samples digested with RNase one; ii) samples where we performed competition assays with polyadenylic acid.
Project description:Appropriate expression of most eukaryotic genes requires the removal of introns from their pre-messenger RNAs (pre-mRNAs), a process catalyzed by the spliceosome. In higher eukaryotes a large family of auxiliary factors known as SR proteins can improve the splicing efficiency of transcripts containing suboptimal splice sites by interacting with distinct sequences present in those pre-mRNAs. The yeast Saccharomyces cerevisiae lacks functional equivalents of most of these factors; thus, it has been unclear whether the spliceosome could effectively distinguish among transcripts. To address this question, we have used a microarray-based approach to examine the effects of mutations in 18 highly conserved core components of the spliceosomal machinery. The kinetic profiles reveal clear differences in the splicing defects of particular pre-mRNA substrates. Most notably, the behaviors of ribosomal protein gene transcripts are generally distinct from other intron-containing transcripts in response to several spliceosomal mutations. However, dramatically different behaviors can be seen for some pairs of transcripts encoding ribosomal protein gene paralogs, suggesting that the spliceosome can readily distinguish between otherwise highly similar pre-mRNAs. The ability of the spliceosome to distinguish among its different substrates may therefore offer an important opportunity for yeast to regulate gene expression in a transcript-dependent fashion. Given the high level of conservation of core spliceosomal components across eukaryotes, we expect that these results will significantly impact our understanding of how regulated splicing is controlled in higher eukaryotes as well. Keywords: time course, splicing mutant, splicing-specific microarray
Project description:RNA degradation pathways underlie RNA processing, the regulation of RNA levels, and the surveillance of aberrant or poorly functional RNAs in cells. Here we provide transcriptome-wide RNA-binding profiles of 30 general RNA degradation factors in the yeast S. cerevisiae. The profiles define the distribution of factors between RNA classes. They are also consistent with the canonical degradation pathway for closed-loop forming mRNAs after deadenylation. Modeling based on mRNA half-lives suggests that most degradation factors bind already to intact mRNAs, whereas decapping factors are recruited only for mRNA degradation, consistent with decapping being a rate-limiting step. Global analysis suggests that the nuclear surveillance machinery, including the complexes Nrd1/Nab3, TRAMP4, and the exosome, targets aberrant nuclear RNAs, pre-processes snoRNAs, and regulates attenuated genes. Finally, mRNA transcript optimality is the most predictive feature for binding of decapping factors and the Xrn1 exonuclease to mRNA, consistent with rapid 5´-degradation of inefficiently translated mRNAs.
Project description:To investigate the possible range of additional RNase P substrates in vivo a strand-specific, high-density microarray was used to analyze what RNA accumulates with a mutation in the catalytic RNA subunit of nuclear RNase P in Saccharomyces cerevisiae. A wide variety of noncoding RNAs were shown to accumulate, suggesting nuclear RNase P participates in the turnover of normally unstable nuclear RNAs. In some cases, the accumulated noncoding RNAs were shown to be antisense to transcripts that commensurately decreased in abundance. Pre-mRNAs containing introns also accumulated broadly, consistent with either compromised splicing or failure to efficiently turnover pre-mRNAs that do not enter the splicing pathway. Taken together with the high complexity of the nuclear RNase P holoenzyme and its relatively non-specific capacity to bind and cleave mixed sequence RNAs, these data suggest nuclear RNase P facilitates turnover of nuclear RNAs in addition to its role in pre-tRNA biogenesis.
| E-MEXP-3140 | biostudies-arrayexpress
Project description:Competition drives niche differentiation between ammonia oixidizing microorganisms
Project description:General discard pathways eliminate unprocessed and irregular pre-mRNAs to control the quality of gene expression. In contrast to such general pre-mRNA decay, we describe here a nuclear pre-mRNA degradation pathway that controls the expression of select intron-containing genes. We show that the fission yeast nuclear poly(A)-binding protein, Pab2, and the nuclear exosome subunit, Rrp6, are the main factors involved in this polyadenylation-dependent pre-mRNA degradation pathway. Transcriptome analysis and intron swapping experiments revealed that inefficient splicing is important to dictate susceptibility to Pab2-dependent pre-mRNA decay. We also show that negative splicing regulation can promote the poor splicing efficiency required for this pre-mRNA decay pathway, and in doing so identify a mechanism of cross-regulation between paralogous ribosomal proteins through nuclear pre-mRNA decay. Our findings unveil a layer of regulation in the nucleus in which the turnover of specific pre-mRNAs, besides the turnover of mature mRNAs, is used to control gene expression.