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Rodriguez JM, Abascal F, Cerdán-Vélez D, Gómez LM, Vázquez J, Tress ML. Evidence for widespread translation of 5' untranslated regions. Nucleic Acids Res 2024; 52:8112-8126. [PMID: 38953162 DOI: 10.1093/nar/gkae571] [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: 02/07/2024] [Revised: 06/07/2024] [Accepted: 06/19/2024] [Indexed: 07/03/2024] Open
Abstract
Ribosome profiling experiments support the translation of a range of novel human open reading frames. By contrast, most peptides from large-scale proteomics experiments derive from just one source, 5' untranslated regions. Across the human genome we find evidence for 192 translated upstream regions, most of which would produce protein isoforms with extended N-terminal ends. Almost all of these N-terminal extensions are from highly abundant genes, which suggests that the novel regions we detect are just the tip of the iceberg. These upstream regions have characteristics that are not typical of coding exons. Their GC-content is remarkably high, even higher than 5' regions in other genes, and a large majority have non-canonical start codons. Although some novel upstream regions have cross-species conservation - five have orthologues in invertebrates for example - the reading frames of two thirds are not conserved beyond simians. These non-conserved regions also have no evidence of purifying selection, which suggests that much of this translation is not functional. In addition, non-conserved upstream regions have significantly more peptides in cancer cell lines than would be expected, a strong indication that an aberrant or noisy translation initiation process may play an important role in translation from upstream regions.
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Affiliation(s)
- Jose Manuel Rodriguez
- Cardiovascular Proteomics Laboratory, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), 28029 Madrid, Spain
| | - Federico Abascal
- Somatic Evolution Group, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridgeshire CB10 1SA. UK
| | - Daniel Cerdán-Vélez
- Bioinformatics Unit, Spanish National Cancer Research Centre (CNIO), 28029 Madrid, Spain
| | - Laura Martínez Gómez
- Bioinformatics Unit, Spanish National Cancer Research Centre (CNIO), 28029 Madrid, Spain
| | - Jesús Vázquez
- Cardiovascular Proteomics Laboratory, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), 28029 Madrid, Spain
| | - Michael L Tress
- Bioinformatics Unit, Spanish National Cancer Research Centre (CNIO), 28029 Madrid, Spain
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2
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Villagra UMM, da Cunha BR, Polachini GM, Henrique T, Stefanini ACB, de Castro TB, da Silva CHTP, Feitosa OA, Fukuyama EE, López RVM, Dias-Neto E, Nunes FD, Severino P, Tajara EH. Expression of Truncated Products at the 5'-Terminal Region of RIPK2 and Evolutive Aspects that Support Their Biological Importance. Genome Biol Evol 2024; 16:evae106. [PMID: 38752399 PMCID: PMC11221433 DOI: 10.1093/gbe/evae106] [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] [Accepted: 05/10/2024] [Indexed: 07/04/2024] Open
Abstract
Alternative splicing is the process of generating different mRNAs from the same primary transcript, which contributes to increase the transcriptome and proteome diversity. Abnormal splicing has been associated with the development of several diseases including cancer. Given that mutations and abnormal levels of the RIPK2 transcript and RIP-2 protein are frequent in tumors, and that RIP-2 modulates immune and inflammatory responses, we investigated alternative splicing events that result in partial deletions of the kinase domain at the N-terminus of RIP-2. We also investigated the structure and expression of the RIPK2 truncated variants and isoforms in different environments. In addition, we searched data throughout Supraprimates evolution that could support the biological importance of RIPK2 alternatively spliced products. We observed that human variants and isoforms were differentially regulated following temperature stress, and that the truncated transcript was more expressed than the long transcript in tumor samples. The inverse was found for the longer protein isoform. The truncated variant was also detected in chimpanzee, gorilla, hare, pika, mouse, rat, and tree shrew. The fact that the same variant has been preserved in mammals with divergence times up to 70 million years raises the hypothesis that it may have a functional significance.
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Affiliation(s)
- Ulises M M Villagra
- Faculty of Exact Sciences, Biotechnology and Molecular Biology Institute (IBBM), National University of La Plata-CCT, CONICET, La Plata, Argentina
| | - Bianca R da Cunha
- Department of Molecular Biology, School of Medicine of São José do Rio Preto/FAMERP, São José do Rio Preto, SP, Brazil
- Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo/USP, São Paulo, SP, Brazil
| | - Giovana M Polachini
- Department of Molecular Biology, School of Medicine of São José do Rio Preto/FAMERP, São José do Rio Preto, SP, Brazil
| | - Tiago Henrique
- Department of Molecular Biology, School of Medicine of São José do Rio Preto/FAMERP, São José do Rio Preto, SP, Brazil
| | - Ana Carolina Buzzo Stefanini
- Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo/USP, São Paulo, SP, Brazil
| | - Tialfi Bergamin de Castro
- Department of Molecular Biology, School of Medicine of São José do Rio Preto/FAMERP, São José do Rio Preto, SP, Brazil
- Microbial Pathogenesis Department, University of Maryland Baltimore, School of Dentistry, Baltimore, MD, USA
| | - Carlos H T P da Silva
- Computational Laboratory of Pharmaceutical Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo/USP, Ribeirão Preto, SP, Brazil
| | - Olavo A Feitosa
- Computational Laboratory of Pharmaceutical Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo/USP, Ribeirão Preto, SP, Brazil
| | - Erica E Fukuyama
- Head and Neck Surgery Department, Arnaldo Vieira de Carvalho Cancer Institute, São Paulo, SP, Brazil
| | - Rossana V M López
- Comprehensive Center for Precision Oncology, Center for Translational Research in Oncology, State of São Paulo Cancer Institute—ICESP, Clinics Hospital, Sao Paulo University Medical School, São Paulo, SP, Brazil
| | - Emmanuel Dias-Neto
- Laboratory of Medical Genomics, A.C. Camargo Cancer Center, São Paulo, SP, Brazil
| | - Fabio D Nunes
- Department of Stomatology, School of Dentistry, University of São Paulo/USP, São Paulo, SP, Brazil
| | - Patricia Severino
- Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo/USP, São Paulo, SP, Brazil
- Albert Einstein Research and Education Institute, Hospital Israelita Albert Einstein, São Paulo, SP, Brazil
| | - Eloiza H Tajara
- Department of Molecular Biology, School of Medicine of São José do Rio Preto/FAMERP, São José do Rio Preto, SP, Brazil
- Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of São Paulo/USP, São Paulo, SP, Brazil
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3
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Lewin LE, Daniels KG, Hurst LD. Genes for highly abundant proteins in Escherichia coli avoid 5' codons that promote ribosomal initiation. PLoS Comput Biol 2023; 19:e1011581. [PMID: 37878567 PMCID: PMC10599525 DOI: 10.1371/journal.pcbi.1011581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 10/09/2023] [Indexed: 10/27/2023] Open
Abstract
In many species highly expressed genes (HEGs) over-employ the synonymous codons that match the more abundant iso-acceptor tRNAs. Bacterial transgene codon randomization experiments report, however, that enrichment with such "translationally optimal" codons has little to no effect on the resultant protein level. By contrast, consistent with the view that ribosomal initiation is rate limiting, synonymous codon usage following the 5' ATG greatly influences protein levels, at least in part by modifying RNA stability. For the design of bacterial transgenes, for simple codon based in silico inference of protein levels and for understanding selection on synonymous mutations, it would be valuable to computationally determine initiation optimality (IO) scores for codons for any given species. One attractive approach is to characterize the 5' codon enrichment of HEGs compared with the most lowly expressed genes, just as translational optimality scores of codons have been similarly defined employing the full gene body. Here we determine the viability of this approach employing a unique opportunity: for Escherichia coli there is both the most extensive protein abundance data for native genes and a unique large-scale transgene codon randomization experiment enabling objective definition of the 5' codons that cause, rather than just correlate with, high protein abundance (that we equate with initiation optimality, broadly defined). Surprisingly, the 5' ends of native genes that specify highly abundant proteins avoid such initiation optimal codons. We find that this is probably owing to conflicting selection pressures particular to native HEGs, including selection favouring low initiation rates, this potentially enabling high efficiency of ribosomal usage and low noise. While the classical HEG enrichment approach does not work, rendering simple prediction of native protein abundance from 5' codon content futile, we report evidence that initiation optimality scores derived from the transgene experiment may hold relevance for in silico transgene design for a broad spectrum of bacteria.
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Affiliation(s)
- Loveday E. Lewin
- The Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, United Kingdom
| | - Kate G. Daniels
- The Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, United Kingdom
| | - Laurence D. Hurst
- The Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, United Kingdom
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4
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Cosenza G, Martin P, Garro G, Gallo D, Auzino B, Ciampolini R, Pauciullo A. A novel allelic donkey β-lactogobulin I protein isoform generated by a non-AUG translation initiation codon is associated with a nonsynonymous SNP. J Dairy Sci 2023; 106:4158-4170. [PMID: 37080792 DOI: 10.3168/jds.2022-22598] [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: 07/29/2022] [Accepted: 12/17/2022] [Indexed: 04/22/2023]
Abstract
β-Lactoglobulin I (β-LG I) is one of the most important whey proteins in donkey milk. However, to our knowledge, there has been no study focusing on the full nucleotide sequences of this gene (BLG I). Current investigation of donkey BLG I gene is very limited with only 2 variants (A and B) characterized so far at the protein level. Recently, a new β-LG I variant, with a significantly higher mass (+1,915 Da) than known variants has been detected. In this study, we report the whole nucleotide sequence of the BLG I gene from 2 donkeys, whose milk samples are characterized by the β-LG I SDS-PAGE band with a normal electrophoretic mobility (18,514.25 Da, β-LG I B1 form) the first, and by the presence of a unique β-LG I band with a higher electrophoretic mobility (20,428.5 Da, β-LG I D form) the latter. A high genetic variability was found all over the 2 sequenced BLG I alleles. In particular, 16 polymorphic sites were found in introns, one in the 5' flanking region, 3 SNPs in the 5' untranslated region and one SNP in the coding region (g.458G > A) located at the 40th nucleotide of exon 2 and responsible for the AA substitutions p.Asp28 > Asn in the mature protein. Two SNPs (g.920-922CAC > TGT and g.1871G/A) were genotyped in 93 donkeys of 2 Italian breeds (60 Ragusana and 33 Amiatina, respectively) and the overall frequencies of g.920-922CAC and g.1871A were 0.3065 and 0.043, respectively. Only the rare allele g.1871A was observed to be associated with the slower migrating β-LG I. Considering this genetic diversity and those found in the database, it was possible to deduce at least 5 different alleles (BLG I A, B, B1, C, D) responsible for 4 potential β-LG I translations. Among these alleles, B1 and D are those characterized in the present research, with the D allele of real novel identification. Haplotype data analysis suggests an evolutionary pathway of donkey BLG I gene and a possible phylogenetic map is proposed. Analyses of mRNA secondary structure showed relevant changes in the structures, as consequence of the g.1871G > A polymorphism, that might be responsible for the recognition of an alternative initiation site providing an additional signal peptide. The extension of 19 AA sequence to the mature protein, corresponding to the canonical signal peptide with an additional alanine residue, is sufficient to provide the observed molecular weight of the slower migrating β-LG I encoded by the BLG I D allele.
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Affiliation(s)
- G Cosenza
- Department of Agricultural Sciences, University of Naples "Federico II," 80055 Portici (Na), Italy.
| | - P Martin
- Université Paris-Saclay, INRAE, MICALIS Institute, PAPPSO, 78350 Jouy-en-Josas, France
| | - G Garro
- Department of Agricultural Sciences, University of Naples "Federico II," 80055 Portici (Na), Italy
| | - D Gallo
- Department of Agricultural Sciences, University of Naples "Federico II," 80055 Portici (Na), Italy
| | - B Auzino
- Department of Veterinary Science, University of Pisa, 56100, Italy
| | - R Ciampolini
- Department of Veterinary Science, University of Pisa, 56100, Italy.
| | - A Pauciullo
- Department of Agriculture, Forest and Food Sciences, University of Torino, 10095 Grugliasco (TO), Italy
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5
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Komori T, Hata S, Mabuchi A, Genova M, Harada T, Fukuyama M, Chinen T, Kitagawa D. A CRISPR-del-based pipeline for complete gene knockout in human diploid cells. J Cell Sci 2023; 136:286993. [PMID: 36762651 PMCID: PMC10038147 DOI: 10.1242/jcs.260000] [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: 03/07/2022] [Accepted: 02/02/2023] [Indexed: 02/11/2023] Open
Abstract
The advance of CRISPR/Cas9 technology has enabled us easily to generate gene knockout cell lines by introducing insertion-deletion mutations (indels) at the target site via the error-prone non-homologous end joining repair system. Frameshift-promoting indels can disrupt gene functions by generation of a premature stop codon. However, there is growing evidence that targeted genes are not always knocked out by the indel-based gene disruption. Here, we established a pipeline of CRISPR-del, which induces a large chromosomal deletion by cutting two different target sites, to perform 'complete' gene knockout efficiently in human diploid cells. Quantitative analyses show that the frequency of gene deletion with this approach is much higher than that of conventional CRISPR-del methods. The lengths of the deleted genomic regions demonstrated in this study are longer than those of 95% of the human protein-coding genes. Furthermore, the pipeline enabled the generation of a model cell line having a bi-allelic cancer-associated chromosomal deletion. Overall, these data lead us to propose that the CRISPR-del pipeline is an efficient and practical approach for producing 'complete' gene knockout cell lines in human diploid cells.
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Affiliation(s)
- Takuma Komori
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
| | - Shoji Hata
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO) Program, Japan Science and Technology Agency, Honcho Kawaguchi, 102-8666 Saitama, Japan
| | - Akira Mabuchi
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
| | - Mariya Genova
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, 69120 Heidelberg, Germany
| | - Tomoki Harada
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
| | - Masamitsu Fukuyama
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
| | - Takumi Chinen
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
| | - Daiju Kitagawa
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
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6
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Fedorova AD, Kiniry SJ, Andreev DE, Mudge JM, Baranov PV. Thousands of human non-AUG extended proteoforms lack evidence of evolutionary selection among mammals. Nat Commun 2022; 13:7910. [PMID: 36564405 PMCID: PMC9789052 DOI: 10.1038/s41467-022-35595-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 12/12/2022] [Indexed: 12/24/2022] Open
Abstract
The synthesis of most proteins begins at AUG codons, yet a small number of non-AUG initiated proteoforms are also known. Here we analyse a large number of publicly available Ribo-seq datasets to identify novel, previously uncharacterised non-AUG proteoforms using Trips-Viz implementation of a novel algorithm for detecting translated ORFs. In parallel we analyse genomic alignment of 120 mammals to identify evidence of protein coding evolution in sequences encoding potential extensions. Unexpectedly we find that the number of non-AUG proteoforms identified with ribosome profiling data greatly exceeds those with strong phylogenetic support suggesting their recent evolution. Our study argues that the protein coding potential of human genome greatly exceeds that detectable through comparative genomics and exposes the existence of multiple proteins encoded by the same genomic loci.
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Affiliation(s)
- Alla D Fedorova
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland.
- SFI Centre for Research Training in Genomics Data Science, University College Cork, Cork, Ireland.
| | - Stephen J Kiniry
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Dmitry E Andreev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, RAS, Moscow, Russia
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Jonathan M Mudge
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland.
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7
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Maddi AMA, Kavousi K, Arabfard M, Ohadi H, Ohadi M. Tandem repeats ubiquitously flank and contribute to translation initiation sites. BMC Genom Data 2022; 23:59. [PMID: 35896982 PMCID: PMC9331589 DOI: 10.1186/s12863-022-01075-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 07/18/2022] [Indexed: 12/31/2022] Open
Abstract
Background While the evolutionary divergence of cis-regulatory sequences impacts translation initiation sites (TISs), the implication of tandem repeats (TRs) in TIS selection remains largely elusive. Here, we employed the TIS homology concept to study a possible link between TRs of all core lengths and repeats with TISs. Methods Human, as reference sequence, and 83 other species were selected, and data was extracted on the entire protein-coding genes (n = 1,611,368) and transcripts (n = 2,730,515) annotated for those species from Ensembl 102. Following TIS identification, two different weighing vectors were employed to assign TIS homology, and the co-occurrence pattern of TISs with the upstream flanking TRs was studied in the selected species. The results were assessed in 10-fold cross-validation. Results On average, every TIS was flanked by 1.19 TRs of various categories within its 120 bp upstream sequence, per species. We detected statistically significant enrichment of non-homologous human TISs co-occurring with human-specific TRs. On the contrary, homologous human TISs co-occurred significantly with non-human-specific TRs. 2991 human genes had at least one transcript, TIS of which was flanked by a human-specific TR. Text mining of a number of the identified genes, such as CACNA1A, EIF5AL1, FOXK1, GABRB2, MYH2, SLC6A8, and TTN, yielded predominant expression and functions in the human brain and/or skeletal muscle. Conclusion We conclude that TRs ubiquitously flank and contribute to TIS selection at the trans-species level. Future functional analyses, such as a combination of genome editing strategies and in vitro protein synthesis may be employed to further investigate the impact of TRs on TIS selection. Supplementary Information The online version contains supplementary material available at 10.1186/s12863-022-01075-5.
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8
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Zhang J, Xu C. Gene product diversity: adaptive or not? Trends Genet 2022; 38:1112-1122. [PMID: 35641344 PMCID: PMC9560964 DOI: 10.1016/j.tig.2022.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 04/30/2022] [Accepted: 05/03/2022] [Indexed: 01/24/2023]
Abstract
One gene does not equal one RNA or protein. The genomic revolution has revealed numerous different RNA and protein molecules that can be produced from one gene, such as circular RNAs generated by back-splicing, proteins with residues mismatching the genomic encoding because of RNA editing, and proteins extended in the C terminus via stop codon readthrough in translation. Are these diverse products results of exquisite gene regulations or imprecise biological processes? While there are cases where the gene product diversity appears beneficial, genome-scale patterns suggest that much of this diversity arises from nonadaptive, molecular errors. This finding has important implications for studying the functions of diverse gene products and for understanding the fundamental properties and evolution of cellular life.
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Affiliation(s)
- Jianzhi Zhang
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Chuan Xu
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China
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9
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Andreev DE, Loughran G, Fedorova AD, Mikhaylova MS, Shatsky IN, Baranov PV. Non-AUG translation initiation in mammals. Genome Biol 2022; 23:111. [PMID: 35534899 PMCID: PMC9082881 DOI: 10.1186/s13059-022-02674-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Accepted: 04/14/2022] [Indexed: 12/12/2022] Open
Abstract
Recent proteogenomic studies revealed extensive translation outside of annotated protein coding regions, such as non-coding RNAs and untranslated regions of mRNAs. This non-canonical translation is largely due to start codon plurality within the same RNA. This plurality is often due to the failure of some scanning ribosomes to recognize potential start codons leading to initiation downstream—a process termed leaky scanning. Codons other than AUG (non-AUG) are particularly leaky due to their inefficiency. Here we discuss our current understanding of non-AUG initiation. We argue for a near-ubiquitous role of non-AUG initiation in shaping the dynamic composition of mammalian proteomes.
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10
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Chen P, Michel AH, Zhang J. Transposon insertional mutagenesis of diverse yeast strains suggests coordinated gene essentiality polymorphisms. Nat Commun 2022; 13:1490. [PMID: 35314699 PMCID: PMC8938418 DOI: 10.1038/s41467-022-29228-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 03/01/2022] [Indexed: 12/18/2022] Open
Abstract
Due to epistasis, the same mutation can have drastically different phenotypic consequences in different individuals. This phenomenon is pertinent to precision medicine as well as antimicrobial drug development, but its general characteristics are largely unknown. We approach this question by genome-wide assessment of gene essentiality polymorphism in 16 Saccharomyces cerevisiae strains using transposon insertional mutagenesis. Essentiality polymorphism is observed for 9.8% of genes, most of which have had repeated essentiality switches in evolution. Genes exhibiting essentiality polymorphism lean toward having intermediate numbers of genetic and protein interactions. Gene essentiality changes tend to occur concordantly among components of the same protein complex or metabolic pathway and among a group of over 100 mitochondrial proteins, revealing molecular machines or functional modules as units of gene essentiality variation. Most essential genes tolerate transposon insertions consistently among strains in one or more coding segments, delineating nonessential regions within essential genes.
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Affiliation(s)
- Piaopiao Chen
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Agnès H Michel
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
| | - Jianzhi Zhang
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, 48109, USA.
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11
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Palazzo AF, Kejiou NS. Non-Darwinian Molecular Biology. Front Genet 2022; 13:831068. [PMID: 35251134 PMCID: PMC8888898 DOI: 10.3389/fgene.2022.831068] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 01/24/2022] [Indexed: 12/14/2022] Open
Abstract
With the discovery of the double helical structure of DNA, a shift occurred in how biologists investigated questions surrounding cellular processes, such as protein synthesis. Instead of viewing biological activity through the lens of chemical reactions, this new field used biological information to gain a new profound view of how biological systems work. Molecular biologists asked new types of questions that would have been inconceivable to the older generation of researchers, such as how cellular machineries convert inherited biological information into functional molecules like proteins. This new focus on biological information also gave molecular biologists a way to link their findings to concepts developed by genetics and the modern synthesis. However, by the late 1960s this all changed. Elevated rates of mutation, unsustainable genetic loads, and high levels of variation in populations, challenged Darwinian evolution, a central tenant of the modern synthesis, where adaptation was the main driver of evolutionary change. Building on these findings, Motoo Kimura advanced the neutral theory of molecular evolution, which advocates that selection in multicellular eukaryotes is weak and that most genomic changes are neutral and due to random drift. This was further elaborated by Jack King and Thomas Jukes, in their paper “Non-Darwinian Evolution”, where they pointed out that the observed changes seen in proteins and the types of polymorphisms observed in populations only become understandable when we take into account biochemistry and Kimura’s new theory. Fifty years later, most molecular biologists remain unaware of these fundamental advances. Their adaptionist viewpoint fails to explain data collected from new powerful technologies which can detect exceedingly rare biochemical events. For example, high throughput sequencing routinely detects RNA transcripts being produced from almost the entire genome yet are present less than one copy per thousand cells and appear to lack any function. Molecular biologists must now reincorporate ideas from classical biochemistry and absorb modern concepts from molecular evolution, to craft a new lens through which they can evaluate the functionality of transcriptional units, and make sense of our messy, intricate, and complicated genome.
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12
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Xu C, Zhang J. Mammalian circular RNAs result largely from splicing errors. Cell Rep 2021; 36:109439. [PMID: 34320353 PMCID: PMC8365531 DOI: 10.1016/j.celrep.2021.109439] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 04/13/2021] [Accepted: 07/02/2021] [Indexed: 12/20/2022] Open
Abstract
Ubiquitous in eukaryotes, circular RNAs (circRNAs) comprise a large class of mostly non-coding RNAs produced by back-splicing. Although some circRNAs have demonstrated biochemical activities, whether most circRNAs are functional is unknown. Here, we test the hypothesis that circRNA production primarily results from splicing error and so is deleterious instead of beneficial. In support of the error hypothesis, our analysis of RNA sequencing data from 11 shared tissues of humans, macaques, and mice finds that (1) back-splicing is much rarer than linear-splicing, (2) the rate of back-splicing diminishes with the splicing amount, (3) the overall prevalence of back-splicing in a species declines with its effective population size, and (4) circRNAs are overall evolutionarily unconserved. We estimate that more than 97% of the observed circRNA production is deleterious. We identify a small number of functional circRNA candidates, and the genome-wide trend strongly suggests that circRNAs are largely non-functional products of splicing errors.
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Affiliation(s)
- Chuan Xu
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders of Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China; Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Jianzhi Zhang
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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