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Porat J, Slat VA, Rader SD, Bayfield MA. The fission yeast methyl phosphate capping enzyme Bmc1 guides 2'-O-methylation of the U6 snRNA. Nucleic Acids Res 2023; 51:8805-8819. [PMID: 37403782 PMCID: PMC10484740 DOI: 10.1093/nar/gkad563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 06/15/2023] [Accepted: 06/23/2023] [Indexed: 07/06/2023] Open
Abstract
Splicing requires the tight coordination of dynamic spliceosomal RNAs and proteins. U6 is the only spliceosomal RNA transcribed by RNA Polymerase III and undergoes an extensive maturation process. In humans and fission yeast, this includes addition of a 5' γ-monomethyl phosphate cap by members of the Bin3/MePCE family as well as snoRNA guided 2'-O-methylation. Previously, we have shown that the Bin3/MePCE homolog Bmc1 is recruited to the S. pombe telomerase holoenzyme by the LARP7 family protein Pof8, where it acts in a catalytic-independent manner to protect the telomerase RNA and facilitate holoenzyme assembly. Here, we show that Bmc1 and Pof8 are required for the formation of a distinct U6 snRNP that promotes 2'-O-methylation of U6, and identify a non-canonical snoRNA that guides this methylation. We also show that the 5' γ-monomethyl phosphate capping activity of Bmc1 is not required for its role in promoting snoRNA guided 2'-O-methylation, and that this role relies on different regions of Pof8 from those required for Pof8 function in telomerase. Our results are consistent with a novel role for Bmc1/MePCE family members in stimulating 2'-O-methylation and a more general role for Bmc1 and Pof8 in guiding noncoding RNP assembly beyond the telomerase RNP.
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Affiliation(s)
| | - Viktor A Slat
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada
| | - Stephen D Rader
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada
- Department of Chemistry and Biochemistry, University of Northern British Columbia, Prince George, Canada
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Anil AT, Choudhary K, Pandian R, Gupta P, Thakran P, Singh A, Sharma M, Mishra SK. Splicing of branchpoint-distant exons is promoted by Cactin, Tls1 and the ubiquitin-fold-activated Sde2. Nucleic Acids Res 2022; 50:10000-10014. [PMID: 36095128 PMCID: PMC9508853 DOI: 10.1093/nar/gkac769] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/22/2022] [Accepted: 08/27/2022] [Indexed: 11/13/2022] Open
Abstract
Intron diversity facilitates regulated gene expression and alternative splicing. Spliceosomes excise introns after recognizing their splicing signals: the 5'-splice site (5'ss), branchpoint (BP) and 3'-splice site (3'ss). The latter two signals are recognized by U2 small nuclear ribonucleoprotein (snRNP) and its accessory factors (U2AFs), but longer spacings between them result in weaker splicing. Here, we show that excision of introns with a BP-distant 3'ss (e.g. rap1 intron 2) requires the ubiquitin-fold-activated splicing regulator Sde2 in Schizosaccharomyces pombe. By monitoring splicing-specific ura4 reporters in a collection of S. pombe mutants, Cay1 and Tls1 were identified as additional regulators of this process. The role of Sde2, Cay1 and Tls1 was further confirmed by increasing BP-3'ss spacings in a canonical tho5 intron. We also examined BP-distant exons spliced independently of these factors and observed that RNA secondary structures possibly bridged the gap between the two signals. These proteins may guide the 3'ss towards the spliceosome's catalytic centre by folding the RNA between the BP and 3'ss. Orthologues of Sde2, Cay1 and Tls1, although missing in the intron-poor Saccharomyces cerevisiae, are present in intron-rich eukaryotes, including humans. This type of intron-specific pre-mRNA splicing appears to have evolved for regulated gene expression and alternative splicing of key heterochromatin factors.
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Affiliation(s)
- Anupa T Anil
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Karan Choudhary
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Rakesh Pandian
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Praver Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Poonam Thakran
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Arashdeep Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Monika Sharma
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Shravan Kumar Mishra
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
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Hujová P, Souček P, Radová L, Kramárek M, Kováčová T, Freiberger T. Nucleotides in both donor and acceptor splice sites are responsible for choice in NAGNAG tandem splice sites. Cell Mol Life Sci 2021; 78:6979-6993. [PMID: 34596691 PMCID: PMC11072513 DOI: 10.1007/s00018-021-03943-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/08/2021] [Accepted: 09/15/2021] [Indexed: 12/31/2022]
Abstract
Among alternative splicing events in the human transcriptome, tandem NAGNAG acceptor splice sites represent an appreciable proportion. Both proximal and distal NAG can be used to produce two splicing isoforms differing by three nucleotides. In some cases, the upstream exon can be alternatively spliced as well, which further increases the number of possible transcripts. In this study, we showed that NAG choice in tandem splice site depends considerably not only on the concerned acceptor, but also on the upstream donor splice site sequence. Using an extensive set of experiments with systematically modified two-exonic minigene systems of AFAP1L2 or CSTD gene, we recognized the third and fifth intronic upstream donor splice site position and the tandem acceptor splice site region spanning from -10 to +2, including NAGNAG itself, as the main drivers. In addition, competition between different branch points and their composition were also shown to play a significant role in NAG choice. All these nucleotide effects appeared almost additive, which explained the high variability in proximal versus distal NAG usage.
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Affiliation(s)
- Pavla Hujová
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic
| | - Přemysl Souček
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic.
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic.
| | - Lenka Radová
- Central European Institute of Technology, Masaryk University, 62500, Brno, Czech Republic
| | - Michal Kramárek
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
| | - Tatiana Kováčová
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic
| | - Tomáš Freiberger
- Centre for Cardiovascular Surgery and Transplantation, 65691, Brno, Czech Republic
- Faculty of Medicine, Masaryk University, 62500, Brno, Czech Republic
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Targeting Alternative Splicing for Reversal of Cellular Senescence in the Context of Aesthetic Aging. Plast Reconstr Surg 2021; 147:25S-32S. [PMID: 33347071 DOI: 10.1097/prs.0000000000007618] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
SUMMARY Cellular senescence is a state of stable cell cycle arrest that has increasingly been linked with cellular, tissue, and organismal aging; targeted removal of senescent cells brings healthspan and lifespan benefits in animal models. Newly emerging approaches to specifically ablate or rejuvenate senescent cells are now the subject of intense study to explore their utility to provide novel treatments for the aesthetic signs and diseases of aging in humans. Here, we discuss different strategies that are being trialed in vitro, and more recently in vivo, for the targeted removal or reversal of senescent cells. Finally, we describe the evidence for a newly emerging molecular mechanism that may underpin senescence; dysregulation of alternative splicing. We will explore the potential of restoring splicing regulation as a novel "senotherapeutic" approach and discuss strategies by which this could be integrated into the established portfolio of skin aging therapeutics.
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Fang S, Hou X, Qiu K, He R, Feng X, Liang X. The occurrence and function of alternative splicing in fungi. FUNGAL BIOL REV 2020. [DOI: 10.1016/j.fbr.2020.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Li BJ, Zhu ZX, Qin H, Meng ZN, Lin HR, Xia JH. Genome-Wide Characterization of Alternative Splicing Events and Their Responses to Cold Stress in Tilapia. Front Genet 2020; 11:244. [PMID: 32256528 PMCID: PMC7093569 DOI: 10.3389/fgene.2020.00244] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 02/28/2020] [Indexed: 12/15/2022] Open
Abstract
Alternative splicing (AS) is an important post-transcriptional regulatory mechanism for cells to generate transcript variability and proteome diversity. No systematic investigation of AS events among different tissues in response to stressors is available for tilapia currently. In this study, AS among different tissues was identified and the cold stress-related AS events were explored in a Nile tilapia (Oreochromis niloticus) line based on 42 RNA-seq datasets using a bioinformatics pipeline. 14,796 (82.76%; SD = 2,840) of the expression genes showed AS events. The two most abundant AS types were alternative transcription start site (TSS) and terminal site (TTS) in tilapia. Testis, brain and kidney possess the most abundant AS gene number, while the blood, muscle and liver possess the least number in each tissue. Furthermore, 208 differentially alternative splicing (DAS) genes in heart and 483 DAS in brain in response to cold stress. The number of AS types for alternative exon end, exon skipping and retention of single intron increased significantly under cold stress. GO enrichment and pathway overrepresentation analysis indicated that many DAS genes, e.g., genes in circadian clock pathway, may influence expression of downstream genes under cold stress. Our study revealed that AS exists extensively in tilapia and plays an important role in cold adaption.
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Affiliation(s)
| | | | | | | | | | - Jun Hong Xia
- State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, College of Life Sciences, Sun Yat-sen University, Guangzhou, China
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Annalora AJ, Marcus CB, Iversen PL. Alternative Splicing in the Nuclear Receptor Superfamily Expands Gene Function to Refine Endo-Xenobiotic Metabolism. Drug Metab Dispos 2020; 48:272-287. [DOI: 10.1124/dmd.119.089102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/31/2019] [Indexed: 12/20/2022] Open
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Annalora AJ, Jozic M, Marcus CB, Iversen PL. Alternative splicing of the vitamin D receptor modulates target gene expression and promotes ligand-independent functions. Toxicol Appl Pharmacol 2018; 364:55-67. [PMID: 30552932 DOI: 10.1016/j.taap.2018.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 12/04/2018] [Accepted: 12/10/2018] [Indexed: 02/07/2023]
Abstract
Alternative splicing modulates gene function by creating splice variants with alternate functions or non-coding RNA activity. Naturally occurring variants of nuclear receptor (NR) genes with dominant negative or gain-of-function phenotypes have been documented, but their cellular roles, regulation, and responsiveness to environmental stress or disease remain unevaluated. Informed by observations that class I androgen and estrogen receptor variants display ligand-independent signaling in human cancer tissues, we questioned whether the function of class II NRs, like the vitamin D receptor (VDR), would also respond to alternative splicing regulation. Artificial VDR constructs lacking exon 3 (Dex3-VDR), encoding part of the DNA binding domain (DBD), and exon 8 (Dex8-VDR), encoding part of the ligand binding domain (LBD), were transiently transfected into DU-145 cells and stably-integrated into Caco-2 cells to study their effect on gene expression and cell viability. Changes in VDR promoter signaling were monitored by the expression of target genes (e.g. CYP24A1, CYP3A4 and CYP3A5). Ligand-independent VDR signaling was observed in variants lacking exon 8, and a significant loss of gene suppressor function was documented for variants lacking exon 3. The gain-of-function behavior of the Dex8-VDR variant was recapitulated in vitro using antisense oligonucleotides (ASO) that induce the skipping of exon 8 in wild-type VDR. ASO targeting the splice acceptor site of exon 8 significantly stimulated ligand-independent VDR reporter activity and the induction of CYP24A1 above controls. These results demonstrate how alternative splicing can re-program NR gene function, highlighting novel mechanisms of toxicity and new opportunities for the use of splice-switching oligonucleotides (SSO) in precision medicine.
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Affiliation(s)
- Andrew J Annalora
- Department of Environmental and Molecular Toxicology, Oregon State University, 1007 Agriculture & Life Sciences Building, Corvallis, OR 97331; USA.
| | - Marija Jozic
- Department of Environmental and Molecular Toxicology, Oregon State University, 1007 Agriculture & Life Sciences Building, Corvallis, OR 97331; USA
| | - Craig B Marcus
- Department of Environmental and Molecular Toxicology, Oregon State University, 1007 Agriculture & Life Sciences Building, Corvallis, OR 97331; USA
| | - Patrick L Iversen
- Department of Environmental and Molecular Toxicology, Oregon State University, 1007 Agriculture & Life Sciences Building, Corvallis, OR 97331; USA; LS Pharma, 884 Park St., Lebanon, OR 97355; USA
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