Abstract
m
5
C is one of the longest-known RNA modifications, however, its developmental dynamics, functions, and evolution in mRNAs remain largely unknown. Here, we generate quantitative mRNA m
5
C ...maps at different stages of development in 6 vertebrate and invertebrate species and find convergent and unexpected massive methylation of maternal mRNAs mediated by NSUN2 and NSUN6. Using
Drosophila
as a model, we reveal that embryos lacking maternal mRNA m
5
C undergo cell cycle delays and fail to timely initiate maternal-to-zygotic transition, implying the functional importance of maternal mRNA m
5
C. From invertebrates to the lineage leading to humans, two waves of m
5
C regulatory innovations are observed: higher animals gain cis-directed NSUN2-mediated m
5
C sites at the 5' end of the mRNAs, accompanied by the emergence of more structured 5'UTR regions; humans gain thousands of trans-directed NSUN6-mediated m
5
C sites enriched in genes regulating the mitotic cell cycle. Collectively, our studies highlight the existence and regulatory innovations of a mechanism of early embryonic development and provide key resources for elucidating the role of mRNA m
5
C in biology and disease.
Regulation of protein translation initiation is tightly associated with cell growth and survival. Here, we identify Paip1, the Drosophila homolog of the translation initiation factor PAIP1, and ...analyze its role during development. Through genetic analysis, we find that loss of Paip1 causes reduced protein translation and pupal lethality. Furthermore, tissue specific knockdown of Paip1 results in apoptotic cell death in the wing imaginal disc. Paip1 depletion leads to increased proteotoxic stress and activation of the integrated stress response (ISR) pathway. Mechanistically, we show that loss of Paip1 promotes phosphorylation of eIF2α via the kinase PERK, leading to apoptotic cell death. Moreover, Paip1 depletion upregulates the transcription factor gene Xrp1, which contributes to apoptotic cell death and eIF2α phosphorylation. We further show that loss of Paip1 leads to an increase in Xrp1 translation mediated by its 5'UTR. These findings uncover a novel mechanism that links translation impairment to tissue homeostasis and establish a role of ISR activation and Xrp1 in promoting cell death.
Mutations or dysregulated expression of NF-kappaB-activating protein (NKAP) family genes have been found in human cancers. How NKAP family gene mutations promote tumor initiation and progression ...remains to be determined. Here, we characterized dNKAP, the Drosophila homolog of NKAP, and showed that impaired dNKAP function causes genome instability and tumorigenic growth in a Drosophila epithelial tumor model. dNKAP-knockdown wing imaginal discs exhibit tumorigenic characteristics, including tissue overgrowth, cell-invasive behavior, abnormal cell polarity, and cell adhesion defects. dNKAP knockdown causes both R-loop accumulation and DNA damage, indicating the disruption of genome integrity. Further analysis showed that dNKAP knockdown induces c-Jun N-terminal kinase (JNK)-dependent apoptosis and causes aberrant cell proliferation in distinct cell populations. Activation of the Notch and JAK/STAT signaling pathways contributes to the tumorigenic growth of dNKAP-knockdown tissues. Furthermore, JNK signaling is essential for dNKAP depletion-mediated cell invasion. Transcriptome analysis of dNKAP-knockdown tissues confirmed the misregulation of signaling pathways involved in promoting tumorigenesis and revealed abnormal regulation of metabolic pathways. dNKAP knockdown and oncogenic Ras, Notch, or Yki mutations show synergies in driving tumorigenesis, further supporting the tumor-suppressive role of dNKAP. In summary, this study demonstrates that dNKAP plays a tumor-suppressive role by preventing genome instability in Drosophila epithelia and thus provides novel insights into the roles of human NKAP family genes in tumor initiation and progression.
Tumor-infiltrating myeloid cells (TIMs) are crucial cell populations involved in tumor immune escape, and their functions are regulated by multiple epigenetic mechanisms. The precise regulation mode ...of RNA N6-methyladenosine (m6A) modification in controlling TIM function is still poorly understood. Our study revealed that the increased expression of methyltransferase-like 3 (METTL3) in TIMs was correlated with the poor prognosis of colon cancer patients, and myeloid deficiency of METTL3 attenuated tumor growth in mice. METTL3 mediated m6A modification on Jak1 mRNA in TIMs, the m6A-YTHDF1 axis enhanced JAK1 protein translation efficiency and subsequent phosphorylation of STAT3. Lactate accumulated in tumor microenvironment potently induced METTL3 upregulation in TIMs via H3K18 lactylation. Interestingly, we identified two lactylation modification sites in the zinc-finger domain of METTL3, which was essential for METTL3 to capture target RNA. Our results emphasize the importance of lactylation-driven METTL3-mediated RNA m6A modification for promoting the immunosuppressive capacity of TIMs.
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•H3K18 lactylation increases Mettl3 expression in tumor-infiltrating myeloid cells•METTL3-mediated m6A modification on Jak1 mRNA promotes its protein translation•METTL3/m6A/JAK1/STAT3 axis strengthens immunosuppressive functions of myeloid cells•Lactylation on zinc-finger domain of METTL3 enhances its capture of m6A-modified RNA
Xiong et al. discovered that lactate in tumor microenvironment is a key factor for inducing the expression and function of RNA methyltransferase METTL3. METTL3-mediated m6A modification potently enhances the immunosuppressive functions of tumor-infiltrating myeloid cells to promote tumor immune escape.
m
C is one of the longest-known RNA modifications, however, its developmental dynamics, functions, and evolution in mRNAs remain largely unknown. Here, we generate quantitative mRNA m
C maps at ...different stages of development in 6 vertebrate and invertebrate species and find convergent and unexpected massive methylation of maternal mRNAs mediated by NSUN2 and NSUN6. Using Drosophila as a model, we reveal that embryos lacking maternal mRNA m
C undergo cell cycle delays and fail to timely initiate maternal-to-zygotic transition, implying the functional importance of maternal mRNA m
C. From invertebrates to the lineage leading to humans, two waves of m
C regulatory innovations are observed: higher animals gain cis-directed NSUN2-mediated m
C sites at the 5' end of the mRNAs, accompanied by the emergence of more structured 5'UTR regions; humans gain thousands of trans-directed NSUN6-mediated m
C sites enriched in genes regulating the mitotic cell cycle. Collectively, our studies highlight the existence and regulatory innovations of a mechanism of early embryonic development and provide key resources for elucidating the role of mRNA m
C in biology and disease.
Tumor-infiltrating myeloid cells (TIMs) are crucial cell populations involved in tumor immune escape, and their functions are regulated by multiple epigenetic mechanisms. The precise regulation mode ...of RNA N
-methyladenosine (m
A) modification in controlling TIM function is still poorly understood. Our study revealed that the increased expression of methyltransferase-like 3 (METTL3) in TIMs was correlated with the poor prognosis of colon cancer patients, and myeloid deficiency of METTL3 attenuated tumor growth in mice. METTL3 mediated m
A modification on Jak1 mRNA in TIMs, the m
A-YTHDF1 axis enhanced JAK1 protein translation efficiency and subsequent phosphorylation of STAT3. Lactate accumulated in tumor microenvironment potently induced METTL3 upregulation in TIMs via H3K18 lactylation. Interestingly, we identified two lactylation modification sites in the zinc-finger domain of METTL3, which was essential for METTL3 to capture target RNA. Our results emphasize the importance of lactylation-driven METTL3-mediated RNA m
A modification for promoting the immunosuppressive capacity of TIMs.
