Microarray analysis of isoginkgetin-treated HCT116 and HCT116p53-/- cells
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ABSTRACT: Isoginkgetin (IGG) is a small molecule inhibitor of the spliceosome although the direct target remains elusive. Widespread failure to accurately remove introns poses a risk to cells and organisms through the potential production of aberrant mRNAs and proteins. The cellular responses to accumulation of these intermediates and/or the direct interference of spliceosome assembly itself may constitute a splicing stress but this is not well defined yet. We used oligonucleotide microarrays to assess genome wide changes in gene expression associated with exposure to IGG in HCT116 cells and an isogenic subline lacking the p53 tumor suppressor that responds to a variety of transcriptional stresses (Oncogene 18 (3), 583-592). Two of the 3 enriched pathways identified using PANTHER analysis of differentially expressed transcripts are linked to the ATF4 transcription factor and these effects are p53-independent.
Project description:Activating transcription factor 4 (ATF4) is activated during cellular stress through a pathway called the integrated stress response (ISR). We had previously reported that the splicing inhibitor isoginkgetin (IGG) activates ATF4 and ATF4-dependent transcripts. To determine the role of ATF4 in the transcriptional response to IGG, we used tandem CRISPR cas9 gene editing to create an ATF4 deficient HCT116 (colon cancer) cell line. We completed RNA sequencing on HCT116 parental and HCT116 ATF4 deficient cells treated with IGG, and thapsigargin (Tg), a positive control for ATF4 activation. We found that IGG led to the differential expression of 76 transcripts, and 58 of these were dependent on ATF4. Tg led to a far more robust transcriptional response, which appeared to be less ATF4 dependent.
Project description:Purpose: Our previous studies have identified Isoginkgetin as an inducer of autophagic cell death in hepatocellular carcinoma. We set out to analyze how isoginkgetin regulates gene expression in HepG2 cells. Methods: RNA-seq was performed with two repetitions in HepG2 followed by treatment with DMSO and 20 μM Isoginkgetin for 24 h. Conclusions: Isoginkgetin treatment reduces the expression of glucose transporters in HepG2 cells.
Project description:Purpose: Our previous studies have identified isoginkgetin as an inducer of autophagic cell death in hepatocellular carcinoma. We set out to analyze how isoginkgetin regulates the genome-wide enhancer activity in HepG2 cells. Methods: ChIP-seq for H3K27ac was performed in HepG2 followed by treatment with 20 μM isoginkgetin for 24 h. Conclusions: Isoginkgetin treatment reduces the expression of glucose transporters and inhibts SLC2A1 enhancer activity in HepG2 cells.
Project description:Purpose: Our previous studies have identified isoginkgetin as an inducer of autophagic cell death in hepatocellular carcinoma. We set out to analyze how isoginkgetin regulates the genome-wide enhancer activity in HepG2 cells. Methods: ChIP-seqs for H3K4me, H4K8ac, H3K27me3 and H3K9ac were performed in HepG2 followed by treatment with 20 μM isoginkgetin for 24 h. Conclusions: Isoginkgetin treatment reduces the expression of glucose transporters and inhibts SLC2A1 enhancer activity in HepG2 cells.
Project description:Pharmacological perturbation is a powerful tool for understanding gene expression, but identification of the specific steps of this multi-step process targeted by small molecules remains challenging. Here we apply total RNA-Seq to distinguish specific pharmacological effects on transcription and pre-mRNA processing, revealing unexpectedly that the splicing inhibitor isoginkgetin blocks transcription elongation.An RNA-Seq screen reveals that the compounds TBBz and CYT387 mimic the transcriptional effects of isoginkgetin and are inhibitors of CSNK2A2, suggesting that isoginkgetin blocks transcription elongation via inhibition of CSNK2A2. Our results reveal RNA-Seq screening as a tool for disentangling complex pharmacological effects on gene expression.
Project description:The success of cancer immunotherapy relies on the induction of an immunoprotective response targeting tumor antigens (TAs) presented on MHC-I molecules. We demonstrated that the splicing inhibitor isoginkgetin and its water-soluble and non-toxic derivative IP2 act at the production stage of the Pioneer Translation Products (PTPs). We showed that IP2 increases PTP-derived antigen presentation in cancer cells in vitro and impairs tumor growth in vivo. IP2 action is long-lasting and dependent on the CD8+ T cell response against TAs. We observed that the antigen repertoire displayed on MHC-I molecules at the surface of MCA205 fibrosarcoma is modified upon treatment with IP2. In particular, IP2 enhances the presentation of an exon-derived epitope from the tumor suppressor nischarin. The combination of IP2 with a peptide vaccine targeting the nischarin-derived epitope showed a synergistic antitumor effect. These findings identify the spliceosome as a druggable target for the development of epitope-based immunotherapies.
Project description:Primary telomerase RNA transcripts are processed into shorter mature forms that assemble into a complex with the catalytic subunit and provide the template for telomerase activity. In diverse fungi telomerase RNA 3â end processing involves a single cleavage reaction by the spliceosome akin to the first step of splicing. Longer forms of human telomerase RNA (hTR) have been reported, but how the mature form of precisely 451 nucleotides is generated is still unknown. We now show that the splicing inhibitor isoginkgetin causes accumulation of long hTR transcripts, but find no evidence for a direct role for splicing in hTR processing. Instead, isoginkgetin mimics the effects of inhibiting the RNA exosome. Depletion of exosome components and accessory factors reveals functions for the cap binding complex (CBC) and the nuclear exosome targeting (NEXT) complex in hTR turnover. Whereas longer transcripts are predominantly degraded, shorter precursor RNAs are oligo-adenylated by TRF4-2 and either processed by poly (A) specific ribonuclease (PARN) or degraded by the exosome. Our results reveal that hTR biogenesis involves a kinetic competition between RNA processing and quality control pathways and suggest new treatment options for dyskeratosis congenita caused by mutations in RNA processing factors. We cloned and sequenced 3â ends by RLM-RACE coupled with high-throughput sequencing to gain further insights into hTR processing.
Project description:We developed SCAN-seq2, a high-throughput and highly sensitive single-cell RNA sequencing method based on the TGS platform. Our study demonstrated that SCAN-seq2 improves upon the previous method, SCAN-seq, in terms of sensitivity and throughput. By using reference-guided assembly of single-cell data, we were able to identify thousands of novel full-length RNA isoforms, including cell type-specific expression patterns of pseudogenes. We also accurately determined V(D)J rearrangement events in T and B cells. Lastly, we found that treatment of HepG2 and Hela cells with the spliceosome inhibitor Isoginkgetin (IGG) resulted in a subpopulation of cells with distinct apoptosis features. Our study provides a promising new tool for single-cell transcriptome research. The source code for SCAN-seq2 data analysis pipelines is available at https://github.com/liuzhenyu-yyy/SCAN-seq2 .