Effect of Heat stress on m6A modification in CaSki cell
Ontology highlight
ABSTRACT: N6-methyladenosine (m6A) occurs extensively on multiple RNA species and is the most abundant internal modification of eukaryotic messenger RNA (mRNA). RNA m6A methylation is a dynamic and reversible process subjected to regulation by three categories of m6A modifier proteins, including m6A methyltransferases/writers (e.g., METTL3/14 methyltransferase complex and METTL16), m6A demethylases/erasers (e.g., FTO and ALKBH5) and m6A binding proteins/readers (e.g., YTH family proteins and IGF2BPs). The dynamic and adjustable nature makes m6A a key regulator in RNA metabolism, and the fate of m6A-modified RNA is modulated by m6A readers. Previous studies have demonstrated that fever can benefit survival of cancer patients, and currently hyperthermia (elevating body temperature beyond normal) is either administered alone or in combination with radiotherapy or chemotherapy to treat various neoplasms with unclear mechanisms. Accruing evidence has revealed favorable effects of fever/hyperthermia in cancer treatment through affecting the properties of oncogenic proteins (e.g., stability, posttranslational modification, ability to interact with other molecules). Accordingly, we sought to investigate whether and how heat stress affects cancer development by m6A modification.
Project description:Heat shock induces a cell response leading to profound changes in genome expression. Recently, N6-methyladenosine (m6A) RNA modification has been implicated in this response, but with limited information of its role in the heat-induced reprograming of gene expression. Most of m6A molecular and cellular functions rely on m6A readers and the best characterized m6A readers are members of the YTH-domain-containing protein family present from yeast to humans. To investigate the function of the nuclear m6A reader YTHDC1, we characterized its binding partners.
Project description:Oxaliplatin as a first-line drug frequently causes the chemo-resistance on colorectal cancer (CRC). N6-methyladenosine (m6A) methylation has been largely acknowledged in multiple biological functions. However, the molecular mechanisms underlying the m6A methylation in modulating anticancer drug resistance in CRC are still obscure. In present study, RIP-seq was conducted to investigate the occupancy of N6-methyladenosine RNA binding protein 3 (YTHDF3) served as “readers” that can recognize m6A modification site in HCT116 cells with oxaliplatin resistance (HCT116R). Then, YTHDF3 was knockdown by siRNA in HCT116 cells with oxaliplatin resistance, and RIP-seq was further conducted to investigate m6A methylation of HCT116, HCT116R and HCT116R cells with YTHDF3 knockdown.
Project description:The N6-methyladenosine (m6A) is the most abundant internal modification in almost all eukaryotic messenger RNAs, and is dynamically regulated. Therefore, identification of m6A readers is especially important in determining the cellular function of m6A. YTHDF2 has recently been characterized as the first m6A reader that regulates the cytoplasmic stability of methylated RNA. Here we show that YTHDC1 is a nuclear m6A reader and report the crystal structure of the YTH domain of YTHDC1 bound to m6A-containing RNA. We further determined the structure of another YTH domain, YTHDF1, and found that the YTH domain utilizes a conserved aromatic cage to specifically recognize the methyl group of m6A. Our structural characterizations of the YTHDC1-m6A RNA complex also shed light on the molecular basis for the preferential binding of the GG(m6A)C sequence by YTHDC1 and confirm the YTH domain as a specific m6A RNA reader. PAR-CLIP (Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation) was applied to human YTHDC1 protein to identify its binding sites.
Project description:The internal N6-methyladenosine (m6A) methylation of eukaryotic nuclear RNA controls post-transcriptional gene expression, which is regulated by methyltransferases (writers), demethylases (erasers), and m6A-binding proteins (readers) in cells. The YTH domain family proteins (YTHDF1–3) bind to m6A-modified cellular RNAs and affect RNA metabolism and processing. Here, we show that YTHDF1–3 proteins recognize m6A-modified HIV-1 RNA and inhibit HIV-1 infection in cell lines and primary CD4+ T-cells. We further mapped the YTHDF1–3 binding sites in HIV-1 RNA from infected cells. We found that the overexpression of YTHDF proteins in cells inhibited HIV-1 infection mainly by decreasing HIV-1 reverse transcription, while knockdown of YTHDF1–3 in cells had the opposite effects. Moreover, silencing the m6A writers decreased HIV-1 Gag protein expression in virus-producing cells, while silencing the m6A erasers increased Gag expression. Our findings suggest an important role of m6A modification of HIV-1 RNA in viral infection and HIV-1 protein synthesis.
Project description:<p>Despite the nuclear localization of the m6A machinery, the genomes of multiple exclusively-cytoplasmic RNA viruses, such as chikungunya (CHIKV) and dengue (DENV), are reported to be extensively m6A-modified. However, these findings are mostly based on m6A-seq, an antibody-dependent technique with a high rate of false positives. Here, we addressed the presence of m6A in CHIKV and DENV RNAs. For this, we combined m6A-seq and the antibody-independent SELECT and nanopore direct RNA sequencing techniques with functional, molecular, and mutagenesis studies. Following this comprehensive analysis, we found no evidence of m6A modification in CHIKV or DENV transcripts. Furthermore, depletion of key components of the host m6A machinery did not affect CHIKV or DENV infection. Moreover, CHIKV or DENV infection had no effect on the m6A machinery’s localization. Our results challenge the prevailing notion that m6A modification is a general feature of cytoplasmic RNA viruses and underscore the importance of validating RNA modifications with orthogonal approaches.</p>
Project description:m6A methylation is the prevalent post-transcriptional modification in eukaryotic mRNAs and provides an essential layer of regulation in organismal development and in disease. The information encoded by m6A methylation is integrated into existing RNA regulatory networks by the binding of an expanding list of m6A readers. An important question is how protein readers that do not contain a canonical m6A-specific YTH domain recognize methylated RNA. Here, we show that the non-canonical reader IMP1 directly recognises the m6A group using a dedicated hydrophobic platform in the KH4 domain, creating a stable and high affinity interaction with the methylated RNA targets. Notably, the recognition of the m6A group is independent from the underlying sequence context, but is layered upon IMP1 strong sequence specificity for GGAC RNA. Together, our data indicate that, contrarily to the well-characterised YTH readers, IMP1 recognises and binds both m6A-methylated and non-methylated RNA targets with high affinity. This suggests that m6A methylation does not provide a general layer of control of IMP1 function, but rather plays a directed role in specific regulatory pathways.
Project description:One prevalent modification, N6-methyladenosine (m6A), is a dynamic and reversible process regulated by methyltransferases (the "writers"), demethylases (the "erasers"), and m6A-binding proteins (the "readers"). Its abnormal changes are closely associated with the development and progression of human cancers. m6A demethylases, such as FTO and ALKBH5, eliminate the m6A modification from RNA, thus regulating the overall levels of this modification. Here, we show that the m6A demethylase ALKBH5 is highly expressed after ionizing radiation treatment. We conducted polysome profiling alongside RNA sequencing in both control and ALKBH5-KO GSC 83 cells and identified genes with differential translational efficiency due to ALKBH5 KO. We further elucidated that genes, whose translational efficiencies (TEs) were down-regulated after ALKBH5 knockout, were enriched in stemness properties and DNA repair. Overall, our findings imply that ALKBH5 facilitates the selective translation of mRNAs encoding pathways related to stemness and resistance to therapeutic interventions.
Project description:N6-methyladenosine (m6A) is the most predominant internal mRNA modification in eukaryotes, recognised by its reader proteins (so-called m6A-readers) for regulating subsequent mRNA fates – splicing, export, localization, decay, stability and translation – to control several biological processes. Although a few m6A-readers have been identified, yet the list is incomplete. Here, we identify a new m6A-reader protein, MOV10, in mouse embryonic stem cells (mESCs). MOV10 recognises m6A-containing mRNAs with a conserved GGm6ACU motif. Mechanistic studies uncover that MOV10 bound m6A-containing mRNAs facilitate mRNA decay within the cytoplasmic processing bodies (P-bodies) in an m6A-dependent manner. Moreover, MOV10 decays the Gsk-3ß mRNA through m6A that stabilises the ß-CATENIN expression of a Wnt/ß-catenin signalling pathway to regulate downstream target expression of NANOG for maintaining the mESC state. Thus, our findings reveal how a newly identified m6A-reader, MOV10 mediates mRNA decay via m6A that impact ESC biology.
Project description:N6-methyladenosine (m6A) is the most abundant internal mRNA nucleotide modification in mammals, regulating critical aspects of cell physiology and differentiation. The YTHDF proteins are the primary readers of m6A modifications and exert physiological functions of m6A in the cytosol. Elucidating the regulatory mechanisms of YTHDF proteins is critical to understanding m6A biology. Here, we report a mechanism that protein post-translational modifications control the biological functions of the YTHDF proteins. We find that YTHDF1 and YTHDF3, but not YTHDF2, carry high levels of nutrient-sensing O-GlcNAc modifications. O-GlcNAc modification attenuates the translation promoting function of YTHDF1 and YTHDF3 by blocking their interactions with proteins associated with mRNA translation. We further demonstrate that O-GlcNAc modifications on YTHDF1 and YTHDF2 regulate the assembly, stability, and disassembly of stress granule, facilitating rapid exchange of m6A-modified mRNAs in stress granules for recovery from stress. Therefore, our results discover an important regulatory pathway of YTHDF functions, adding an additional layer of complexity to the post-transcriptional regulation function of mRNA m6A.
Project description:To study the effect of m6A modifications on subcellular mRNA localization we depleted m6A readers Ythdf1, -2 and -3 with shRNAs from mouse primary cortical neurons (mPCN) and sequenced neuritic and somatic compartments in parallel with scrambled shRNA control.