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:We conduct herein a systematic study of mRNA recognition and consequent polyadenylation processing of the Arabidopsis mRNA by m6A reader protein CPSF70. Transcriptome-wide characterization of CPSF70-binding sites supporting the recognition m6A-methylated mRNA with CPSF70, and the results of which linked polyadenylation signals recognition. We then perform 3’end sequencing with A-seq2 to identify CPSF70-dependent APA process, showing that CPSF70 modulate m6A–dependent polyadenylation with FUE recognition.
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:Human neurodevelopment requires differentiating neurons to establish large networks of connections in a highly stereotyped manner. Neuronal differentiation in particular, requires RNA-binding proteins to spatiotemporally regulate thousands of different mRNAs. Yet, how these proteins precisely relate to neuronal development and coordinate the expression of functionally coherent genes in a cell type specific manner is only partially understood. To address this, we sought to understand how the paradigmatic RNA-binding protein IMP1/IGF2BP1, an essential developmental factor, selects and regulates its RNA targets transcriptome-wide during the differentiation of human neurons. We used a combination of systemic and molecular analyses to show that IMP1 directly binds to and regulates the expression of a large set of mRNAs that govern microtubule assembly, an essential process and a key driver of neuronal differentiation. We also show that m6A methylation during the transition from neural precursors to neurons drives both the selection of IMP1 mRNA targets and their translation potential. Our findings establish m6A methylation as a key mechanism coordinating the regulatory action of IMP1 on human neuronal architecture.
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.
Project description:m6A methylation provides an essential layer of regulation in organismal development, and is aberrant in a range of cancers and neuro-pathologies. The information encoded by m6A methylation is integrated into existing RNA regulatory networks by RNA binding proteins that recognise methylated sites, the m6A readers. m6A readers include a well-characterised class of dedicated proteins, the YTH proteins, as well as a broader group of multi-functional regulators where recognition of m6A is only partially understood. Molecular insight in this recognition is essential to build a mechanistic understanding of global m6A regulation. In this study, we show that the reader IMP1 recognises the m6A using a dedicated hydrophobic platform that assembles on the methyl moiety, creating a stable high-affinity interaction. This recognition is conserved across evolution and independent from the underlying sequence context but is layered upon the strong sequence specificity of IMP1 for GGAC RNA. This leads us to propose a concept for m6A regulation where methylation plays a context-dependent role in the recognition of selected IMP1 targets that is dependent on the cellular concentration of available IMP1, differing from that observed for the YTH proteins.