Project description:Mammalian body temperature oscillates with the time of the day and is altered in diverse pathological conditions. We recently identified a body temperature-sensitive thermometer-like kinase, which alters SR protein phosphorylation and thereby globally controls alternative splicing (AS). AS can generate unproductive variants which are recognized and degraded by diverse mRNA decay pathways – including nonsense-mediated decay (NMD). Here we show extensive coupling of body temperature-controlled AS to mRNA decay, leading to global control of temperature-dependent gene expression (GE). Temperature-controlled, decay-inducing splicing events are evolutionarily conserved and pervasively found within RNA-binding proteins, including most SR proteins. AS-coupled poison exon inclusion is essential for rhythmic GE of SR proteins and has a global role in establishing temperature-dependent rhythmic GE profiles, both, in mammals under circadian body temperature cycles and in plants in response to ambient temperature changes. Together, these data identify body temperature-driven AS coupled mRNA decay as an evolutionary ancient, core clock-independent mechanism to generate rhythmic GE.
Project description:The highly conserved protein eIF5A found in archaea and all eucaryotes uniquely contains the posttranslationally formed amino acid hypusine. Despite being essential the functions of this protein and its modification remain unclear. To gain more insight into these functions temperature sensitive mutants of the human EIF5A1 were characterized in the yeast Saccharomyces cerevisiae. EIF5A is proposed to be an RNA binding protein. Thus, we used microarrays to identify special RNA subsets of up- and downregulation that are influenced by a limited eIF5A function in strains expressing a point mutated form of eIF5A. Experiment Overall Design: Wild-type and mutant yeast strains were grown at 25°C following total RNA extraction and hybridization on Affymetrix microarrays. cRNA probes derived from RNA preparations were obtained from four isogenic, haploid strains from each of the wild-type and the mutant. This ensured that changes in the transcriptome could be attributed to the impaired HYP function of V81G rather than to differences in the genetic background. Therefore, two groups of 4 datasets (per wild-type W303-WT and mutant W303-V81G strains) were generated after hybridisation to the micro arrays.
Project description:Using RNA-Seq analysis of nonsense-mediated mRNA decay (NMD) mutant strains, we show that many Saccharomyces cerevisiae intron-containing genes exhibit usage of alternative splice sites, but most transcripts generated by splicing from these sites are non-functional because they introduce premature termination codons leading to transcript degradation by NMD. Analysis of splicing mutants combined with NMD inactivation revealed the role of specific splicing factors in governing the use of these alternative splice sites and identified novel functions for Prp17p in enhancing the use of branchpoint-proximal upstream 3M-bM-^@M-^Y splice sites and for Prp18p in suppressing the usage of a non-canonical AUG 3M-bM-^@M-^Y-splice site. The use of non-productive alternative splice sites can limit the expression of some transcripts and can be increased in stress conditions in a promoter-dependent manner, contributing to the down-regulation of genes during stress. These results reveal that alternative splicing is frequent in S.cerevisiae but masked by RNA degradation and that the use of alternative splice sites is mostly aimed at controlling transcript levels rather than increasing proteome diversity. mRNA-Seq profiling of 3 mutants in the nonsense-mediated mRNA decay pathway and wildtype yeast
Project description:Expression of mutant spliceosome proteins (e.g., U2AF1S34F, SF3B1K700E, or SRSF2P95H) alters RNA splicing in myeloid neoplasms, leading to increased production of nonsense transcripts. We have previously shown that inhibiting the nonsense–mediated RNA decay (NMD) pathway, which is responsible for degradation of nonsense transcripts, preferentially kills cells expressing mutant spliceosome proteins. In this study, we used a novel inhibitor (SMG1i-63) of the kinase SMG1, a key regulator of NMD, to provide in vivo evidence that NMD is also a therapeutic vulnerability for splicing factor mutant myeloid neoplasms. We show that primary mouse acute myeloid leukemia cells and human K562 leukemia cell lines expressing splicing factor mutants were more sensitive than wild-type cells to in vivo inhibition of SMG1 (SMG1i). Disruption of NMD activity by SMG1i led to increased R-loops levels in spliceosome wild-type cells, which are further increased in U2AF1S34F treated cells. This R-loop accumulation was accompanied by an increase in DNA damage. Degradation of R-loops with RNase H1 rescued spliceosome mutant cells from NMD inhibition-induced cell death, indicating that R-loop formation is a primary mechanism of drug sensitivity. In U2AF1S34F cells, SMG1i led to increased detection of NMD transcript isoforms (with reduced but detectable protein levels) for DNA repair genes, including ATR and RAD51. Consequently, SMG1i-induced cell death in splicing factor mutant leukemias could be further enhanced by inhibition of the DNA damage response proteins ATR or RAD51. This study shows that in vivo targeting of NMD is a therapeutic strategy to treat myeloid neoplasms with aberrant splicing.
Project description:Identification of novel, highly penetrant, breast cancer susceptibility genes will require the application of additional strategies beyond that of traditional linkage and candidate gene approaches. Approximately one-third of inherited genetic diseases, including breast cancer susceptibility, are caused by frameshift or nonsense mutations that truncate the protein product [1]. Transcripts harbouring premature termination codons are selectively and rapidly degraded by the nonsense-mediated mRNA decay (NMD) pathway. Blocking the NMD pathway in any given cell will stabilise these mutant transcripts, which can then be detected using gene expression microarrays. This technique, known as gene identification by nonsense-mediated mRNA decay inhibition (GINI), has proved successful in identifying sporadic nonsense mutations involved in many different cancer types. However, the approach has not yet been applied to identify germline mutations involved in breast cancer. We therefore attempted to use GINI on lymphoblastoid cell lines (LCLs) from multiple-case, non-BRCA1/2 breast cancer families in order to identify additional high-risk breast cancer susceptibility genes. We applied GINI to a total of 24 LCLs,established from breast-cancer affected and unaffected women from three multiple-case non-BRCA1/2 breast cancer families. We then used Illumina gene expression microarrays to identify transcripts stabilised by the NMD inhibition. Total RNA obtained from the lymphoblastoid cell lines derived from 24 individuals.
Project description:eIF5A is an essential translation elongation factor present in all eukaryotes, and the only known protein to follow a post-translational modification called hypusination. Here, we performed a wide analysis of ribosome dynamics in S. cerevisiae eIF5A depleted cells using 5Pseq (Pelechano et al. 2015 PMID 26046441). This method allows the study of ribosome dynamics, by sequencing 5’ phosphorylated mRNA co-translational degradation intermediates. Since eIF5A is an essential protein in yeast, we used two eIF5A temperature-sensitive strains containing a single Pro83 to Ser mutation (tif51A-1) and double Cys39 to Tyr and Gly118 to Asp mutations (tif51A-3) in the highly expressed gene TIF51A (HYP2) that encodes eIF5A protein (Li et al. 2011 PMID: 24923804).
Project description:The highly conserved protein eIF5A found in archaea and all eucaryotes uniquely contains the posttranslationally formed amino acid hypusine. Despite being essential the functions of this protein and its modification remain unclear. To gain more insight into these functions temperature sensitive mutants of the human EIF5A1 were characterized in the yeast Saccharomyces cerevisiae. EIF5A is proposed to be an RNA binding protein. Thus, we used microarrays to identify special RNA subsets of up- and downregulation that are influenced by a limited eIF5A function in strains expressing a point mutated form of eIF5A. Keywords: two sets of four biological replicates of wild-type and mutant strains
Project description:Nonsense-mediated RNA decay (NMD) is a highly conserved and selective RNA turnover pathway that depends on the endonuclease SMG6. Here, we show that SMG6 is essential for male germ cell differentiation in mice. Germ-cell conditional knockout (cKO) of Smg6 induces extensive transcriptome misregulation, including a failure to eliminate meiotically expressed transcripts in early haploid cells, and accumulation of NMD target mRNAs with long 3’ untranslated regions (UTRs). Loss of SMG6 in the male germline results in complete arrest of spermatogenesis at the early haploid cell stage. We find that SMG6 is strikingly enriched in the chromatoid body (CB), a specialized cytoplasmic granule in male germ cells also harboring PIWI-interacting RNAs (piRNAs) and the piRNA-binding protein PIWIL1.
Project description:Identification of novel, highly penetrant, breast cancer susceptibility genes will require the application of additional strategies beyond that of traditional linkage and candidate gene approaches. Approximately one-third of inherited genetic diseases, including breast cancer susceptibility, are caused by frameshift or nonsense mutations that truncate the protein product [1]. Transcripts harbouring premature termination codons are selectively and rapidly degraded by the nonsense-mediated mRNA decay (NMD) pathway. Blocking the NMD pathway in any given cell will stabilise these mutant transcripts, which can then be detected using gene expression microarrays. This technique, known as gene identification by nonsense-mediated mRNA decay inhibition (GINI), has proved successful in identifying sporadic nonsense mutations involved in many different cancer types. However, the approach has not yet been applied to identify germline mutations involved in breast cancer. We therefore attempted to use GINI on lymphoblastoid cell lines (LCLs) from multiple-case, non-BRCA1/2 breast cancer families in order to identify additional high-risk breast cancer susceptibility genes. We applied GINI to a total of 24 LCLs,established from breast-cancer affected and unaffected women from three multiple-case non-BRCA1/2 breast cancer families. We then used Illumina gene expression microarrays to identify transcripts stabilised by the NMD inhibition.