Project description:Despite the remarkable achievement of immune checkpoint blockade (ICB) therapy, the response rate is relatively low and only a subset of patients can benefit from the treatment. We hypothesize that targeting RNA decay machinery may lead to accumulation of aberrantRNA, triggering interferon (IFN) signaling and sensitizing tumor cells to immunotherapy. With this in mind, we identified an RNA exoribonuclease, XRN1 as a potential target. Silencing of XRN1 suppressed tumor growth in syngeneic immunocompetent mice and potentiated immunotherapy, while silencing of XRN1 alone did not affect tumor growth in immune deficient mice. Mechanistically, XRN1 depletion activated interferon signaling and viral defense pathway; both pathways play determinant roles in regulating immune evasion. We identified aberrant-RNA sensing signaling proteins (RIG-I/MAVS and PKR) in mediating the expression of IFN genes, as depletion of each of them blunted the elevation of anti-viral/IFN signaling in Xrn1 silenced cells. Analysis of pan-cancer CRISPR screening data indicated that IFN signaling triggered by Xrn1 silencing is a common phenomenon, suggesting that the effect of Xrn1 silencing may be extend to multiple types of cancers.
Project description:To determine the effects of inactivation of both the nosense-mediated mRNA decay pathway and the general 5' to 3' decay pathway on yeast mRNA decay, we compared the expression profiles of the wild-type, xrn1, xrn1 upf1, xrn1 nmd2, and xrn1 upf3 strains.
Project description:Despite the remarkable achievement of immune checkpoint blockade (ICB) therapy, the response rate is relatively low and only a subset of patients can benefit from the treatment. We hypothesize that targeting RNA decay machinery may lead to accumulation of aberrantRNA, triggering interferon (IFN) signaling and sensitizing tumor cells to immunotherapy. With this in mind, we identified an RNA exoribonuclease, XRN1 as a potential target. Silencing of XRN1 suppressed tumor growth in syngeneic immunocompetent mice and potentiated immunotherapy, while silencing of XRN1 alone did not affect tumor growth in immune deficient mice. Mechanistically, XRN1 depletion activated interferon signaling and viral defense pathway; both pathways play determinant roles in regulating immune evasion. In murine tumors engrafted on immmunocompetent mice, XRN1 depletion significantly enhanced immune cell infiltration in solid tumors especially in combinatory with PD-1 blockade. We identified aberrant-RNA sensing signaling proteins (RIG-I/MAVS and PKR) in mediating the expression of IFN genes, as depletion of each of them blunted the elevation of anti-viral/IFN signaling in Xrn1 silenced cells. Analysis of pan-cancer CRISPR screening data indicated that IFN signaling triggered by Xrn1 silencing is a common phenomenon, suggesting that the effect of Xrn1 silencing may be extend to multiple types of cancers.
Project description:Antisense (as)lncRNAs are extensively degraded by the nuclear exosome and the cytoplasmic exoribonuclease Xrn1 in the budding yeast Saccharomyces cerevisiae, lacking RNA interference (RNAi). Whether the ribonuclease III Dicer affects aslncRNAs in close RNAi-capable relatives remains unknown. Using genome-wide RNA profiling, here we show that aslncRNAs are primarily targeted by the exosome and Xrn1 in the RNAi-capable budding yeast Naumovozyma castellii, Dicer only affecting Xrn1-sensitive lncRNAs (XUTs) levels in Xrn1-deficient cells. The dcr1 and xrn1 mutants display synergic growth defects, indicating that Dicer becomes critical in absence of Xrn1. Small RNA sequencing showed that Dicer processes aslncRNAs into small RNAs, with a preference for asXUTs. Consistently, Dicer localizes into the cytoplasm. Finally, we observed an expansion of the exosome-sensitive antisense transcriptome in N. castellii compared to S. cerevisiae, suggesting that the presence of cytoplasmic RNAi has reinforced the nuclear RNA surveillance machinery to temper aslncRNAs expression. Our data provide fundamental insights into aslncRNAs metabolism and open perspectives into the possible evolutionary contribution of RNAi in shaping the aslncRNAs transcriptome.
Project description:Xrn1 is a cytoplasmic 5’-3’ exoribonuclease responsible for degradation of multiple types of RNA. Data obtained on yeast model described Xrn1 function in degradation of messenger (m)RNA, Rapid transfer (t)RNA Decay (RTD) of hypomodified and unstable tRNA transcripts as well as maturation of 25S ribosomal (r)RNA and small nucleolar (sno)RNAs. Our group discovered previously that deletion of Xrn1 gene results in stabilization of a group of long non-coding RNAs which are often transcribed antisense to protein-coding genes and may regulate their expression on transcriptional level. However much less is known about human (h)Xrn1 function. Data available from human cell lines confirm involvement of hXrn1 in degradation of mRNA, initiator tRNA methionine and some miRNA. The high sequence similarity of Xrn1 between yeast and man suggests that also its function should be well conserved for hXrn1. Therefore, in this experiment using inducible shRNA we want to define hXrn1 targets by analyzing RNAs that are stabilized after Xrn1 silencing with focus on both coding and non-coding transcripts.
Project description:The main cytoplasmic mRNA decay pathway in yeast uses the 5’-3’ exonuclease Xrn1 (Parker and Song, Nat Struct Mol Biol. 2004 ). This protein shuttles from the cytoplasm to the nucleus, where it has a role as transcription factor (Haimovich et al. Cell 2013). In this work, we find that most of the global phenotypes of an xrn1 mutant are partially complemented by a cytoplasmic version of the paralogous 5’-3’exonuclease Rat1 (cRat1) indicating that this 5’-3’-exonuclease has a similar enzymatic capacity as Xrn1. The lack of a cytoplasmatic 5’-3’-exoribonuclease is the cause of the physiological defects of an xrn1 mutant. The capacity of cRat1 to perform co-translational decay is, however, very limited. The comparison with the strain having a NLS1∆-NLS2∆-Xrn1 version shows that it is slightly deficient in 5’→3’-co-translational decay but much more efficient than cRat1. In both strains, cRat1 and -Xrn1-NLS1&2, the lack of nuclear Xrn1 has a very minor influence on cell growth.
Project description:To study the role of the exonuclease Xrn1 in translational control, we performed ribosome profiling and RNA-seq in Xrn1-depleted cells. By using an auxin-inducible degron, we were able to study immediate effects of Xrn1 depletion in translational control. Therefore, we could overcome experimental limitations associated to stable deletion mutants.
Project description:mRNA homeostasis is favored by crosstalk between transcription and degradation machineries. Both the Ccr4-Not and the Xrn1-decaysome complexes have been described to influence transcription. While Ccr4-Not has been shown to directly stimulate transcription elongation, the information available on how Xrn1 influences transcription is scarce and contradictory. In this study we have addressed this issue by mapping RNA polymerase II (RNA pol II) at high resolution, using CRAC and BioGRO-seq techniques in Saccharomyces cerevisiae. We found significant effects of Xrn1 perturbation on RNA pol II profiles across the genome. RNA pol II profiles at 5’ exhibited significant reductions in slope that were compatible with decreased elongation rates. This phenomenon was also observed soon after the nuclear pool of Xrn1 was depleted. Nucleosome mapping confirmed drastically altered chromatin dynamics. We also found an accumulation of arrested RNA pol II at the 3’ end, immediately upstream of polyadenylation sites of most genes, with particular incidence in those functionally related to regulatory processes. Lack of Xrn1 provoked alterations in RNA pol II CTD phosphorylation and increased recruitment of 3’ pre-mRNA processing factors. However, accumulation of RNA pol II at 3’ ends was rather related to the nucleosomal configuration of those regions.
Project description:mRNA homeostasis is favored by crosstalk between transcription and degradation machineries. Both the Ccr4-Not and the Xrn1-decaysome complexes have been described to influence transcription. While Ccr4-Not has been shown to directly stimulate transcription elongation, the information available on how Xrn1 influences transcription is scarce and contradictory. In this study we have addressed this issue by mapping RNA polymerase II (RNA pol II) at high resolution, using CRAC and BioGRO-seq techniques in Saccharomyces cerevisiae. We found significant effects of Xrn1 perturbation on RNA pol II profiles across the genome. RNA pol II profiles at 5’ exhibited significant reductions in slope that were compatible with decreased elongation rates. This phenomenon was also observed soon after the nuclear pool of Xrn1 was depleted. Nucleosome mapping confirmed drastically altered chromatin dynamics. We also found an accumulation of arrested RNA pol II at the 3’ end, immediately upstream of polyadenylation sites of most genes, with particular incidence in those functionally related to regulatory processes. Lack of Xrn1 provoked alterations in RNA pol II CTD phosphorylation and increased recruitment of 3’ pre-mRNA processing factors. However, accumulation of RNA pol II at 3’ ends was rather related to the nucleosomal configuration of those regions.
Project description:To study the role of the exonuclease Xrn1 in gene expression dynamics under osmotic stress conditions, we performed RNA-seq in Xrn1-depleted cells. By using an auxin-inducible degron, we were able to study immediate effects of Xrn1 depletion in gene expression dynamics. Therefore, we could overcome experimental limitations associated to stable deletion mutants.