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Catlin JP, Schaner Tooley CE. Exploring potential developmental origins of common neurodegenerative disorders. Biochem Soc Trans 2024:BST20230422. [PMID: 38661189 DOI: 10.1042/bst20230422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 03/12/2024] [Accepted: 04/11/2024] [Indexed: 04/26/2024]
Abstract
In the United States, it is now estimated that 6.7 million people over the age of 65 are afflicted by Alzheimer's disease (AD), over 1 million people are living with Parkinson's disease (PD), and over 200 000 have or are at risk for developing Huntington's disease (HD). All three of these neurodegenerative diseases result in the ultimate death of distinct neuronal subtypes, and it is widely thought that age-related damage is the single biggest contributing factor to this neuronal death. However, recent studies are now suggesting that developmental defects during early neurogenesis could also play a role in the pathology of neurodegenerative diseases. Loss or overexpression of proteins associated with HD, PD, and AD also result in embryonic phenotypes but whether these developmental defects slowly unmask over time and contribute to age-related neurodegeneration remains highly debated. Here, we discuss known links between embryonic neurogenesis and neurodegenerative disorders (including common signaling pathways), potential compensatory mechanisms that could delay presentation of neurodegenerative disorders, and the types of model systems that could be used to study these links in vivo.
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Affiliation(s)
- James P Catlin
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, U.S.A
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, U.S.A
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2
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Hobble HV, Schaner Tooley CE. Intrafamily heterooligomerization as an emerging mechanism of methyltransferase regulation. Epigenetics Chromatin 2024; 17:5. [PMID: 38429855 PMCID: PMC10908127 DOI: 10.1186/s13072-024-00530-0] [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: 12/15/2023] [Accepted: 02/10/2024] [Indexed: 03/03/2024] Open
Abstract
Protein and nucleic acid methylation are important biochemical modifications. In addition to their well-established roles in gene regulation, they also regulate cell signaling, metabolism, and translation. Despite this high biological relevance, little is known about the general regulation of methyltransferase function. Methyltransferases are divided into superfamilies based on structural similarities and further classified into smaller families based on sequence/domain/target similarity. While members within superfamilies differ in substrate specificity, their structurally similar active sites indicate a potential for shared modes of regulation. Growing evidence from one superfamily suggests a common regulatory mode may be through heterooligomerization with other family members. Here, we describe examples of methyltransferase regulation through intrafamily heterooligomerization and discuss how this can be exploited for therapeutic use.
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Affiliation(s)
- Haley V Hobble
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA.
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Chen P, Huang R, Hazbun TR. Unlocking the Mysteries of Alpha-N-Terminal Methylation and its Diverse Regulatory Functions. J Biol Chem 2023:104843. [PMID: 37209820 PMCID: PMC10293735 DOI: 10.1016/j.jbc.2023.104843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 05/11/2023] [Accepted: 05/12/2023] [Indexed: 05/22/2023] Open
Abstract
Protein post-translation modifications (PTMs) are a critical regulatory mechanism of protein function. Protein α-N-terminal (Nα) methylation is a conserved PTM across prokaryotes and eukaryotes. Studies of the Nα methyltransferases responsible for Να methylation and their substrate proteins have shown that the PTM involves diverse biological processes, including protein synthesis and degradation, cell division, DNA damage response, and transcription regulation. This review provides an overview of the progress toward the regulatory function of Να methyltransferases and their substrate landscape. More than 200 proteins in humans and 45 in yeast are potential substrates for protein Nα methylation based on the canonical recognition motif, XP[KR]. Based on recent evidence for a less stringent motif requirement, the number of substrates might be increased, but further validation is needed to solidify this concept. A comparison of the motif in substrate orthologs in selected eukaryotic species indicates intriguing gain and loss of the motif across the evolutionary landscape. We discuss the state of knowledge in the field that has provided insights into the regulation of protein Να methyltransferases and their role in cellular physiology and disease. We also outline the current research tools that are key to understanding Να methylation. Finally, challenges are identified and discussed that would aid in unlocking a system-level view of the roles of Να methylation in diverse cellular pathways.
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Affiliation(s)
- Panyue Chen
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907, United States
| | - Rong Huang
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907, United States; Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907, United States
| | - Tony R Hazbun
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907, United States; Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907, United States.
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4
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Parker HV, Schaner Tooley CE. Opposing regulation of the Nα-trimethylase METTL11A by its family members METTL11B and METTL13. J Biol Chem 2023; 299:104588. [PMID: 36889590 PMCID: PMC10166787 DOI: 10.1016/j.jbc.2023.104588] [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: 10/05/2022] [Revised: 03/02/2023] [Accepted: 03/03/2023] [Indexed: 03/08/2023] Open
Abstract
N-terminal protein methylation (Nα-methylation) is a posttranslational modification that influences numerous biological processes by regulating protein stability, protein-DNA interactions, and protein-protein interactions. Although significant progress has been made in understanding the biological roles of Nα-methylation, we still do not completely understand how the modifying methyltransferases are regulated. A common mode of methyltransferase regulation is through complex formation with close family members, and we have previously shown that the Nα-trimethylase METTL11A (NRMT1/NTMT1) is activated through binding of its close homolog METTL11B (NRMT2/NTMT2). Other recent reports indicate that METTL11A co-fractionates with a third METTL family member METTL13, which methylates both the N-terminus and lysine 55 (K55) of eukaryotic elongation factor 1 alpha. Here, using co-immunoprecipitations, mass spectrometry, and in vitro methylation assays, we confirm a regulatory interaction between METTL11A and METTL13 and show that while METTL11B is an activator of METTL11A, METTL13 inhibits METTL11A activity. This is the first example of a methyltransferase being opposingly regulated by different family members. Similarly, we find that METTL11A promotes the K55 methylation activity of METTL13 but inhibits its Nα-methylation activity. We also find that catalytic activity is not needed for these regulatory effects, demonstrating new, noncatalytic functions for METTL11A and METTL13. Finally, we show METTL11A, METTL11B, and METTL13 can complex together, and when all three are present, the regulatory effects of METTL13 take precedence over those of METTL11B. These findings provide a better understanding of Nα-methylation regulation and suggest a model where these methyltransferases can serve in both catalytic and noncatalytic roles.
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Affiliation(s)
- Haley V Parker
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York, USA
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York, USA.
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Parker HV, Tooley JG, Schaner Tooley CE. Optimizing purification and activity assays of N-terminal methyltransferase complexes. Methods Enzymol 2023; 684:71-111. [PMID: 37230594 PMCID: PMC10619428 DOI: 10.1016/bs.mie.2023.02.001] [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] [Indexed: 03/08/2023]
Abstract
In vitro methyltransferase assays have traditionally been carried out with tritiated S-adenosyl-methionine (SAM) as the methyl donor, as site-specific methylation antibodies are not always available for Western or dot blots and structural requirements of many methyltransferases prohibit the use of peptide substrates in luminescent or colorimetric assays. The discovery of the first N-terminal methyltransferase, METTL11A, has allowed for a second look at non-radioactive in vitro methyltransferase assays, as N-terminal methylation is amenable to antibody production and the limited structural requirements of METTL11A allow for its methylation of peptide substrates. We have used a combination of Western blots and luminescent assays to verify substrates of METTL11A and the two other known N-terminal methyltransferases, METTL11B and METTL13. We have also developed these assays for use beyond substrate identification, showing that METTL11A activity is opposingly regulated by METTL11B and METTL13. Here we provide two methods for non-radioactive characterization of N-terminal methylation, Western blots with full-length recombinant protein substrates and luminescent assays with peptide substrates, and describe how each can be additionally adapted to look at regulatory complexes. We will review the advantages and disadvantages of each method in context with the other types of in vitro methyltransferase assays and discuss why these types of assays could be of general use to the N-terminal modification field.
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Affiliation(s)
- Haley V Parker
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, United States
| | - John G Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, United States
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, United States.
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Conner MM, Schaner Tooley CE. Three's a crowd - why did three N-terminal methyltransferases evolve for one job? J Cell Sci 2023; 136:jcs260424. [PMID: 36647772 PMCID: PMC10022744 DOI: 10.1242/jcs.260424] [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] [Indexed: 01/18/2023] Open
Abstract
N-terminal methylation of the α-amine group (Nα-methylation) is a post-translational modification (PTM) that was discovered over 40 years ago. Although it is not the most abundant of the Nα-PTMs, there are more than 300 predicted substrates of the three known mammalian Nα-methyltransferases, METTL11A and METTL11B (also known as NTMT1 and NTMT2, respectively) and METTL13. Of these ∼300 targets, the bulk are acted upon by METTL11A. Only one substrate is known to be Nα-methylated by METTL13, and METTL11B has no proven in vivo targets or predicted targets that are not also methylated by METTL11A. Given that METTL11A could clearly handle the entire substrate burden of Nα-methylation, it is unclear why three distinct Nα-methyltransferases have evolved. However, recent evidence suggests that many methyltransferases perform important biological functions outside of their catalytic activity, and the Nα-methyltransferases might be part of this emerging group. Here, we describe the distinct expression, localization and physiological roles of each Nα-methyltransferase, and compare these characteristics to other methyltransferases with non-catalytic functions, as well as to methyltransferases with both catalytic and non-catalytic functions, to give a better understanding of the global roles of these proteins. Based on these comparisons, we hypothesize that these three enzymes do not just have one common function but are actually performing three unique jobs in the cell.
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Affiliation(s)
- Meghan M. Conner
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
| | - Christine E. Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
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Abstract
The methyltransferase-like (METTL) family is a diverse group of methyltransferases that can methylate nucleotides, proteins, and small molecules. Despite this diverse array of substrates, they all share a characteristic seven-beta-strand catalytic domain, and recent evidence suggests many also share an important role in stem cell biology. The most well characterized family members METTL3 and METTL14 dimerize to form an N6-methyladenosine (m6A) RNA methyltransferase with established roles in cancer progression. However, new mouse models indicate that METTL3/METTL14 are also important for embryonic stem cell (ESC) development and postnatal hematopoietic and neural stem cell self-renewal and differentiation. METTL1, METTL5, METTL6, METTL8, and METTL17 also have recently identified roles in ESC pluripotency and differentiation, while METTL11A/11B, METTL4, METTL7A, and METTL22 have been shown to play roles in neural, mesenchymal, bone, and hematopoietic stem cell development, respectively. Additionally, a variety of other METTL family members are translational regulators, a role that could place them as important players in the transition from stem cell quiescence to differentiation. Here we will summarize what is known about the role of METTL proteins in stem cell differentiation and highlight the connection between their growing importance in development and their established roles in oncogenesis.
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Affiliation(s)
- John G Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 955 Main St., Buffalo, NY, 14203, USA
| | - James P Catlin
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 955 Main St., Buffalo, NY, 14203, USA
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 955 Main St., Buffalo, NY, 14203, USA.
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Conner MM, Parker HV, Falcone DR, Chung G, Schaner Tooley CE. Novel regulation of the transcription factor ZHX2 by N-terminal methylation. Transcription 2022; 13:1-15. [PMID: 35613330 DOI: 10.1080/21541264.2022.2079184] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
N-terminal methylation (Nα-methylation) by the methyltransferase NRMT1 is an important post-translational modification that regulates protein-DNA interactions. Accordingly, its loss impairs functions that are reliant on such interactions, including DNA repair and transcriptional regulation. The global loss of Nα-methylation results in severe developmental and premature aging phenotypes, but given over 300 predicted substrates, it is hard to discern which physiological substrates contribute to each phenotype. One of the most striking phenotypes in NRMT1 knockout (Nrmt1-/-) mice is early liver degeneration. To identify the disrupted signaling pathways leading to this phenotype and the NRMT1 substrates involved, we performed RNA-sequencing analysis of control and Nrmt1-/- adult mouse livers. We found both a significant upregulation of transcripts in the cytochrome P450 (CYP) family and downregulation of transcripts in the major urinary protein (MUP) family. Interestingly, transcription of both families is inversely regulated by the transcription factor zinc fingers and homeoboxes 2 (ZHX2). ZHX2 contains a non-canonical NRMT1 consensus sequence, indicating that its function could be directly regulated by Nα-methylation. We confirmed misregulation of CYP and MUP mRNA and protein levels in Nrmt1-/- livers and verified NRMT1 can methylate ZHX2 in vitro. In addition, we used a mutant of ZHX2 that cannot be methylated to directly demonstrate Nα-methylation promotes ZHX2 transcription factor activity and target promoter occupancy. Finally, we show Nrmt1-/- mice also exhibit early postnatal de-repression of ZHX2 targets involved in fetal liver development. Taken together, these data implicate ZHX2 misregulation as a driving force behind the liver phenotype seen in Nrmt1-/- mice.
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Affiliation(s)
- Meghan M Conner
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Haley V Parker
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Daniela R Falcone
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Gehoon Chung
- Department of Oral Physiology and Program in Neurobiology, School of Dentistry, Seoul National University, Seoul, South Korea
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
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Wong JM, Eirin-Lopez JM. Evolution of methyltransferase like (METTL) proteins in Metazoa: A complex gene family involved in epitranscriptomic regulation and other epigenetic processes. Mol Biol Evol 2021; 38:5309-5327. [PMID: 34480573 PMCID: PMC8662637 DOI: 10.1093/molbev/msab267] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The methyltransferase-like (METTL) proteins constitute a family of seven-beta-strand methyltransferases with S-adenosyl methionine-binding domains that modify DNA, RNA, and proteins. Methylation by METTL proteins contributes to the epigenetic, and in the case of RNA modifications, epitranscriptomic regulation of a variety of biological processes. Despite their functional importance, most investigations of the substrates and functions of METTLs within metazoans have been restricted to model vertebrate taxa. In the present work, we explore the evolutionary mechanisms driving the diversification and functional differentiation of 33 individual METTL proteins across Metazoa. Our results show that METTLs are nearly ubiquitous across the animal kingdom, with most having arisen early in metazoan evolution (i.e., occur in basal metazoan phyla). Individual METTL lineages each originated from single independent ancestors, constituting monophyletic clades, which suggests that each METTL was subject to strong selective constraints driving its structural and/or functional specialization. Interestingly, a similar process did not extend to the differentiation of nucleoside-modifying and protein-modifying METTLs (i.e., each METTL type did not form a unique monophyletic clade). The members of these two types of METTLs also exhibited differences in their rates of evolution. Overall, we provide evidence that the long-term evolution of METTL family members was driven by strong purifying selection, which in combination with adaptive selection episodes, led to the functional specialization of individual METTL lineages. This work contributes useful information regarding the evolution of a gene family that fulfills a variety of epigenetic functions, and can have profound influences on molecular processes and phenotypic traits.
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Affiliation(s)
- Juliet M Wong
- Environmental Epigenetics Laboratory, Institute of Environment, Florida International University, Miami, FL, United States
| | - Jose M Eirin-Lopez
- Environmental Epigenetics Laboratory, Institute of Environment, Florida International University, Miami, FL, United States
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Modulation of N-terminal methyltransferase 1 by an N 6-methyladenosine-based epitranscriptomic mechanism. Biochem Biophys Res Commun 2021; 546:54-58. [PMID: 33561748 DOI: 10.1016/j.bbrc.2021.01.088] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 01/26/2021] [Indexed: 11/22/2022]
Abstract
Protein α-N-methylation is an evolutionarily conserved type of post-translational modification; however, little is known about the regulatory mechanisms for this modification. Methylation at the N6 position of adenosine in mRNAs is dynamic and modulates their stability, splicing, and translational efficiency. Here, we found that the expression of N-terminal methyltransferase 1 (NTMT1) protein is altered by depletion of those genes encoding the reader/writer/eraser proteins of N6-methyladenosine (m6A). We also observed that MRG15 is N-terminally methylated by NTMT1, and this methylation could also be modulated by reader/writer/eraser proteins of m6A. Together, these results revealed a novel m6A-based epitranscriptomic mechanism in regulating protein N-terminal methylation.
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