mRNA half-lives are transcript-specific and vary over a range of more than 100-fold in eukaryotic cells. mRNA stabilities can be regulated by sequence-specific RNA-binding proteins (RBPs), which bind to regulatory sequence elements and modulate the interaction of the mRNA with the cellular RNA degradation machinery. However, it is unclear if this kind of regulation is sufficient to explain the large range of mRNA stabilities. To address this question, we examined the transcriptome of 74 Schizosa ...[more]
Project description:CHX is an inhibitor of translation elongation often used in ribosome profiling experiments. There is evidence that CHX treatment of cells may cause artefacts in the distribution of ribosomes on mRNAs. We investigate this possibility in S. pombe by performing ribosome profiling in the presence and absence of this drug.
Project description:Regulatory elements in the 3 untranslated regions (UTRs) of eukaryotic mRNAs influence mRNA localization, translation, and stability. The length of these regions is determined by the location at which mRNAs are cleaved and polyadenylated. The use of alternative polyadenylation sites is common, and can be regulated in different situations. I present here a new method to identify cleavage and polyadenylation sites (CSs) at the genome-wide level. The approach is strand-specific, avoids RNA enzymatic modification steps that can introduce sequence-specific biases, and uses molecular barcodes to ensure that every identified CS originates from an individual RNA molecule. I applied to create the first comprehensive genome-wide map of polyadenylation sites in the fission yeast Schizosaccharomyces pombe, comprising the analysis of over two million individual mRNAs that defined 10,422 major CSs. CSs were identified for 90% of coding genes and 15% of non-coding RNAs. Alternative polyadenylation was prevalent in both groups, with 61% and 49% of all detected genes, respectively, displaying more than one CS. The specificity of the cleavage reaction was gene-specific, resulting in highly variable levels of heterogeneity in the length of the 3' UTRs. Finally, I show that for both coding and non-coding genes the most common regulatory motif associated with CSs in fission yeast is the canonical human AAUAAA sequence.
Project description:To estimate mRNA steady-state levels we used RNA extracted from logarithmically growing fisson yeast cells on Affymetrix Yeast 2.0 Genechip arrays. The signal intensities from two independent biological repeats were averaged, resulting in measurements for 4818 out of 4962 nuclear protein-coding genes.
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.