Project description:Glioblastoma (GBM) is characterized by an exceptionally high intratumoral heterogeneity. However, the molecular mechanisms underlying the origin of different GBM cell populations remain unclear. Here we found that the composition of ribosomes of GBM cells in the tumor core and edge differ due to alternative RNA splicing. The acidic pH in the core switches pre-mRNA splicing of the ribosomal gene RPL22L1 toward the RPL22L1b isoform. To elucidate the functions of RPL22L1 isoforms we identified proteins that interact with RPL22L1a and RPL22L1b. First, we generated GBM cells with stable expression of Fc-tagged RPL22L1 isoforms. Fc-RPL22L1a and Fc-RPL22L1b together with their binding partners were isolated from neurospheres using magnetic beads and analyzed by LC-MS/MS.
Project description:Glioblastoma (GBM) is characterized by an exceptionally high intratumoral heterogeneity. However, the molecular mechanisms underlying the origin of different GBM cell populations remain unclear. Here we found that the composition of ribosomes of GBM cells in the tumor core and edge differ due to alternative RNA splicing. The acidic pH in the core switches pre-mRNA splicing of the ribosomal gene RPL22L1 toward the RPL22L1b isoform. To elucidate the functions of RPL22L1 isoforms we identified proteins that interact with RPL22L1a and RPL22L1b. First, each isoform was expressed in E. coli and immobilized on magnetic beads. The beads were incubated with GBM cell lysates and proteins bound to the beads were identified using LC-MS/MS.
Project description:Glioblastoma multiforme (GBM) is characterized by an exceptionally high intratumoral heterogeneity. However, the molecular mechanisms underlying the origin of different GBM cell populations remain unclear. Here we found that the composition of ribosomes of GBM cells in the tumor core and edge differ due to alternative RNA splicing. The acidic pH in the core switches pre-mRNA splicing of the ribosomal gene RPL22L1 toward the RPL22L1b isoform. This allows cells to survive acidosis, increases stemness and correlates with worse patient outcome. Mechanistically, RPL22L1b promotes RNA splicing by binding to lncMALAT1 in the nucleus, resulting in its degradation. Contrarily, in the tumor edge region, RPL22L1a interacts with ribosomes in cytoplasm and upregulates translation of multiple mRNAs including TP53. We found that RPL22L1 isoform switch is regulated by SRSF4 and identified the compound, that inhibits this process and decreases tumor growth. These findings demonstrate how distinct GBM cell populations arise during tumor growth. Targeting this mechanism may decrease GBM heterogeneity and facilitate therapy.
Project description:Glioblastoma multiforme (GBM) is characterized by an exceptionally high intratumoral heterogeneity. However, the molecular mechanisms underlying the origin of different GBM cell populations remain unclear. Here we found that the composition of ribosomes of GBM cells in the tumor core and edge differ due to alternative RNA splicing. The acidic pH in the core switches pre-mRNA splicing of the ribosomal gene RPL22L1 toward the RPL22L1b isoform. This allows cells to survive acidosis, increases stemness and correlates with worse patient outcome. Mechanistically, RPL22L1b promotes RNA splicing by binding to lncMALAT1 in the nucleus, resulting in its degradation. Contrarily, in the tumor edge region, RPL22L1a interacts with ribosomes in cytoplasm and upregulates translation of multiple mRNAs including TP53. We found that RPL22L1 isoform switch is regulated by SRSF4 and identified the compound, that inhibits this process and decreases tumor growth. These findings demonstrate how distinct GBM cell populations arise during tumor growth. Targeting this mechanism may decrease GBM heterogeneity and facilitate therapy.
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.
Project description:Microsatellite instability high (MSI-H) tumors are malignant tumors that, despite harboring a high mutational burden, often have intact TP53. One of the most frequent mutations in MSI-H tumors is a frameshift mutation in RPL22, a ribosomal protein. Here, we identified RPL22 as a modulator of MDM4 splicing through an alternative splicing switch in exon 6. RPL22 loss increased MDM4 exon 6 inclusion, cell proliferation, and augmented resistance to the MDM inhibitor Nutlin-3A. RPL22 represses expression of its paralog, RPL22L1, by mediating the splicing of a cryptic exon corresponding to a truncated transcript. Therefore, RPL22 loss is a driver of oncogenic MDM4 induction and key to a common splicing circuit in MSI-H tumors that may inform therapeutic targeting of the MDM4-p53 axis and oncogenic RPL22L1 induction.
Project description:U11 may alter gene expression by affecting the PI3K-Akt signaling pathway and NF-kappa B signaling pathway, regulating alternative splicing events of FN1 and RPL22L1, and ultimately leading to the development of bladder cancer.
Project description:In this study, we analyzed the Arabidopsis homologue of PRMT5, AtPRMT5M-bM-^@M-^Ys function in RNA processing. RNA-seq analyses revealed that AtPRMT5 is involved in a subset of pre-mRNA splicing. Several RNA processing factors involved in regulating flowering time were validated that the corresponding intron retention surely exists in atprmt5 mutants. AtSm proteins can also be methylated by AtPRMT5 in vitro and in vivo, which may be the reasons for the pre-mRNA splicing defects in atprmt5. Contributed by The Institute of Genetics and Developmental Biology (IGDB) of the Chinese Academy of Sciences Investigate the role of AtPRMT5 in pre-mRNA splicing
Project description:Rpl22l1 is a highly conserved ribosomal protein paralog that plays a regulatory role in certain hematopoietic cell lineages. Rpl22l1-deficiency arrests the development of T cells at the DN3 stage. RNA-seq analysis was performed to identify the molecular basis for the arrest
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.