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Gayen A, Mukherjee A, Kumar K, Majumder S, Chakrabarti S, Mukherjee C. The mRNA-capping enzyme localizes to stress granules in the cytoplasm and maintains cap homeostasis of target mRNAs. J Cell Sci 2024; 137:jcs261578. [PMID: 38841902 DOI: 10.1242/jcs.261578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 04/08/2024] [Indexed: 06/07/2024] Open
Abstract
The model of RNA stability has undergone a transformative shift with the revelation of a cytoplasmic capping activity that means a subset of transcripts are recapped autonomously of their nuclear counterparts. The present study demonstrates nucleo-cytoplasmic shuttling of the mRNA-capping enzyme (CE, also known as RNA guanylyltransferase and 5'-phosphatase; RNGTT), traditionally acknowledged for its nuclear localization and functions, elucidating its contribution to cytoplasmic capping activities. A unique nuclear export sequence in CE mediates XPO1-dependent nuclear export of CE. Notably, during sodium arsenite-induced oxidative stress, cytoplasmic CE (cCE) congregates within stress granules (SGs). Through an integrated approach involving molecular docking and subsequent co-immunoprecipitation, we identify eIF3b, a constituent of SGs, as an interactive associate of CE, implying that it has a potential role in guiding cCE to SGs. We measured the cap status of specific mRNA transcripts from U2OS cells that were non-stressed, stressed and recovered from stress, which indicated that cCE-target transcripts lost their caps during stress but remarkably regained cap stability during the recovery phase. This comprehensive study thus uncovers a novel facet of cytoplasmic CE, which facilitates cellular recovery from stress by maintaining cap homeostasis of target mRNAs.
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Affiliation(s)
- Anakshi Gayen
- RNABio Lab, Institute of Health Sciences, Presidency University, Kolkata, West Bengal 700156, India
- CellBio Lab, Institute of Health Sciences, Presidency University, Kolkata, West Bengal 700156, India
| | - Avik Mukherjee
- RNABio Lab, Institute of Health Sciences, Presidency University, Kolkata, West Bengal 700156, India
| | - Krishna Kumar
- Structural Biology and Bioinformatics Division, Council for Scientific and Industrial Research (CSIR) - Indian Institute of Chemical Biology (IICB), Kolkata, West Bengal 700091, India
| | - Shubhra Majumder
- CellBio Lab, Institute of Health Sciences, Presidency University, Kolkata, West Bengal 700156, India
| | - Saikat Chakrabarti
- Structural Biology and Bioinformatics Division, Council for Scientific and Industrial Research (CSIR) - Indian Institute of Chemical Biology (IICB), Kolkata, West Bengal 700091, India
| | - Chandrama Mukherjee
- RNABio Lab, Institute of Health Sciences, Presidency University, Kolkata, West Bengal 700156, India
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Agana BA, Wysocki VH, Schoenberg DR. Cytoplasmic mRNA recapping has limited impact on proteome complexity. Open Biol 2020; 10:200313. [PMID: 33234072 PMCID: PMC7729026 DOI: 10.1098/rsob.200313] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 10/26/2020] [Indexed: 01/25/2023] Open
Abstract
The m7G cap marks the 5' end of all eukaryotic mRNAs, but there are also capped ends that map downstream within spliced exons. A portion of the mRNA transcriptome undergoes a cyclical process of decapping and recapping, termed cap homeostasis, which impacts the translation and stability of these mRNAs. Blocking cytoplasmic capping results in the appearance of uncapped 5' ends at native cap sites but also near downstream cap sites. If translation initiates at these sites the products would lack the expected N-terminal sequences, raising the possibility of a link between mRNA recapping and proteome complexity. We performed a shotgun proteomics analysis on cells carrying an inducible inhibitor of cytoplasmic capping. A total of 21 875 tryptic peptides corresponding to 3565 proteins were identified in induced and uninduced cells. Of these, only 29 proteins significantly increased, and 28 proteins significantly decreased, when cytoplasmic capping was inhibited, indicating mRNA recapping has little overall impact on protein expression. In addition, overall peptide coverage per protein did not change significantly when cytoplasmic capping was inhibited. Together with previous work, our findings indicate cap homeostasis functions primarily in gating mRNAs between translating and non-translating states, and not as a source of proteome complexity.
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Affiliation(s)
- Bernice A. Agana
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Vicki H. Wysocki
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Daniel R. Schoenberg
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USA
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Del Valle Morales D, Trotman JB, Bundschuh R, Schoenberg DR. Inhibition of cytoplasmic cap methylation identifies 5' TOP mRNAs as recapping targets and reveals recapping sites downstream of native 5' ends. Nucleic Acids Res 2020; 48:3806-3815. [PMID: 31996904 PMCID: PMC7144985 DOI: 10.1093/nar/gkaa046] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 12/30/2019] [Accepted: 01/23/2020] [Indexed: 12/20/2022] Open
Abstract
Cap homeostasis is the cyclical process of decapping and recapping that maintains the translation and stability of a subset of the transcriptome. Previous work showed levels of some recapping targets decline following transient expression of an inactive form of RNMT (ΔN-RNMT), likely due to degradation of mRNAs with improperly methylated caps. The current study examined transcriptome-wide changes following inhibition of cytoplasmic cap methylation. This identified mRNAs with 5′-terminal oligopyrimidine (TOP) sequences as the largest single class of recapping targets. Cap end mapping of several TOP mRNAs identified recapping events at native 5′ ends and downstream of the TOP sequence of EIF3K and EIF3D. This provides the first direct evidence for downstream recapping. Inhibition of cytoplasmic cap methylation was also associated with mRNA abundance increases for a number of transcription, splicing, and 3′ processing factors. Previous work suggested a role for alternative polyadenylation in target selection, but this proved not to be the case. However, inhibition of cytoplasmic cap methylation resulted in a shift of upstream polyadenylation sites to annotated 3′ ends. Together, these results solidify cap homeostasis as a fundamental process of gene expression control and show cytoplasmic recapping can impact regulatory elements present at the ends of mRNA molecules.
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Affiliation(s)
- Daniel Del Valle Morales
- Center for RNA Biology, Columbus, OH 43210, USA.,Department of Biological Chemistry and Pharmacology, Columbus, OH 43210, USA.,Molecular, Cellular and Developmental Biology Program, Columbus, OH 43210, USA
| | - Jackson B Trotman
- Center for RNA Biology, Columbus, OH 43210, USA.,Department of Biological Chemistry and Pharmacology, Columbus, OH 43210, USA
| | - Ralf Bundschuh
- Center for RNA Biology, Columbus, OH 43210, USA.,Department of Physics, Columbus, OH 43210, USA.,Department of Chemistry and Biochemistry, Columbus, OH 43210, USA.,Division of Hematology, The Ohio State University, Columbus, OH 43210, USA
| | - Daniel R Schoenberg
- Center for RNA Biology, Columbus, OH 43210, USA.,Department of Biological Chemistry and Pharmacology, Columbus, OH 43210, USA
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Sanderson MR, Badior KE, Fahlman RP, Wevrick R. The necdin interactome: evaluating the effects of amino acid substitutions and cell stress using proximity-dependent biotinylation (BioID) and mass spectrometry. Hum Genet 2020; 139:1513-1529. [PMID: 32529326 DOI: 10.1007/s00439-020-02193-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 06/03/2020] [Indexed: 02/07/2023]
Abstract
Prader-Willi syndrome (PWS) is a neurodevelopmental disorder caused by the loss of function of a set of imprinted genes on chromosome 15q11-15q13. One of these genes, NDN, encodes necdin, a protein that is important for neuronal differentiation and survival. Loss of Ndn in mice causes defects in the formation and function of the nervous system. Necdin is a member of the melanoma-associated antigen gene (MAGE) protein family. The functions of MAGE proteins depend highly on their interactions with other proteins, and in particular MAGE proteins interact with E3 ubiquitin ligases and deubiquitinases to form MAGE-RING E3 ligase-deubiquitinase complexes. Here, we used proximity-dependent biotin identification (BioID) and mass spectrometry (MS) to determine the network of protein-protein interactions (interactome) of the necdin protein. This process yielded novel as well as known necdin-proximate proteins that cluster into a protein network. Next, we used BioID-MS to define the interactomes of necdin proteins carrying coding variants. Variant necdin proteins had interactomes that were distinct from wildtype necdin. BioID-MS is not only a useful tool to identify protein-protein interactions, but also to analyze the effects of variants of unknown significance on the interactomes of proteins involved in genetic disease.
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Affiliation(s)
| | - Katherine E Badior
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.,Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB, Canada
| | - Richard P Fahlman
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.,Department of Oncology, University of Alberta, Edmonton, AB, Canada
| | - Rachel Wevrick
- Department of Medical Genetics, University of Alberta, Edmonton, AB, Canada.
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Berger MR, Alvarado R, Kiss DL. mRNA 5' ends targeted by cytoplasmic recapping cluster at CAGE tags and select transcripts are alternatively spliced. FEBS Lett 2019; 593:670-679. [PMID: 30810230 DOI: 10.1002/1873-3468.13349] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 02/04/2019] [Accepted: 02/22/2019] [Indexed: 11/07/2022]
Abstract
Until cytoplasmic recapping was discovered, decapping was thought to irreversibly destine an mRNA to degradation. Contradicting this idea, we readily observe mRNAs targeted by cytoplasmic capping in uncapped, yet stable forms. 5' rapid amplification of cDNA ends (RACE) shows that nearly all uncapped ends correspond to capped analysis of gene expression tags and that the recapping of ZNF207 mRNA may be restricted to a single splice isoform. Here, a modified RACE approach detected uncapped 5' RNA ends mapping to 46 mRNAs in cells expressing a dominant negative cytoplasmic capping enzyme and in normal cells. Eleven of 46 cloned mRNAs also contained splice isoform-limiting sequences. Collectively, these data reinforce earlier work and suggest that alternative splicing may play a role in targeting transcripts for - and/or determining the position of - cytoplasmic capping.
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Affiliation(s)
- Mikaela R Berger
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
- Department of Biological Chemistry and Pharmacology, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Rolando Alvarado
- Department of Cardiovascular Sciences, Houston Methodist Research Institute, TX, USA
| | - Daniel L Kiss
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
- Department of Biological Chemistry and Pharmacology, The Ohio State University College of Medicine, Columbus, OH, USA
- Department of Cardiovascular Sciences, Houston Methodist Research Institute, TX, USA
- Weill Cornell Medical College, Houston Methodist Research Institute, TX, USA
- Institute of Academic Medicine, Houston Methodist Research Institute, TX, USA
- Houston Methodist Cancer Center, Houston Methodist Research Institute, TX, USA
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