Here, we review recent progress in the underlying mechanisms of intron function, in particular by focusing on unique features of the first intron that is located in close proximity to the transcription start site.  |  The complex gene architecture of multicellular organisms, as contrasted with the simpler gene architecture in single-celled eukaryotes, has prompted widespread speculation that splicing is responsible for emergent complexity in metazoans. Catania F(1), Lynch M. Author information: (1)Department of Biology, Indiana University, Bloomington, Indiana, USA. Finally, it seems quite likely that the nascent RNA most often remains associated with the chromosomal locus being transcribed until processing is complete, possibly acquiring factors related to the transport of the new mRNA to the cytoplasm. The removal of intervening sequences by splicing and the generation of mature 3′-ends by cleavage/polyadenylation are important steps in the processing of nuclear messenger RNA precursors (pre-mRNA). Please enable it to take advantage of the complete set of features! U-richness is a defining feature of plant introns and may function as an intron recognition signal in maize, Alternative pre-mRNA splicing: the logic of combinatorial control, Assessing the application of Ka/Ks ratio test to alternatively spliced exons, Massive Idiosyncratic Exon Skipping Corrects the Nonsense Mutation in Dystrophic Mouse Muscle and Produces Functional Revertant Fibers by Clonal Expansion, The Mouse Histone H2a Gene Contains a Small Element that Facilitates Cytoplasmic Accumulation of Intronless Gene Transcripts and of Unspliced HIV1Related mRNAs, A Perfect Message: RNA Surveillance Minireview and Nonsense-Mediated Decay, Structural and functional features of eukaryotic mRNA untranslated regions, Damage to structures by pyroclastic flows and surges, inferred from nuclear weapons effects, Emerging themes in non-coding RNA quality control, Environmental Plasticity of Programmed DNA Elimination in Paramecium tetraurelia, On the origin(s) and evolution of spliceosomal introns, Transcriptomics data analysis studies and Tutorials. These findings establish Paramecium as a new model system to study the molecular basis and evolutionary significance of developmental plasticity. 2008 Nov 1;6(11):2354-2361. e283. Schematic Example of an Intron-Containing Gene, Schematic Example for a Hypothesized Temporal Succession of Exonization and Intronization Processes, A PTC in a Coding Region Typically Elicits a Translation-Dependent Surveillance Mechanism, Such As NMD, Which Leads to the Degradation of the Aberrant Transcript, Frequency of PTC-Containing Introns in P. tetraurelia, All figure content in this area was uploaded by Francesco Catania, ... Eukaryotic genes are often split by intervening sequences called introns that are removed during and after transcription by the spliceosome and associated splicing proteins. Download PDF: Sorry, we are unable to provide the full text but you may find it at the following location(s): https://doi.org/10.1371/journa... (external link) Retrocopies often inherit introns from parental genes, flanking genomic DNA, or the fusion of transcripts. Transcription of the complementary Template Strand produces a heterogeneous nuclear RNA ( hnRNA ) that is identical ( co-linear ) in 5'-3' orientation and base sequences to the DNA Sense Strand , with the substitution of U for T . Here, I extend this framework further. doi: 10.1101/cshperspect.a032235. By using transient transfection and RNase protection analysis, we demonstrate here that a 100-bp sequence within the H2a coding region permits efficient cytoplasmic accumulation of the globin cDNA transcripts. A new study reports creation of spliceosomal introns in multiple related fungal species by proliferation of cryptic elements. Recently available structures of protein and ribonucleoprotein complexes involved in non-coding RNA quality control are providing a more detailed understanding of this process. First Come, First Served: Sui Generis Features of the First Intron. U1 snRNP (U1) functions in splicing introns and telescripting, which suppresses premature cleavage and polyadenylation (PCPA). The watchtower role of U1 throughout transcription is clear. Conventionally, nonsense mutations within a gene preclude synthesis of a full-length functional protein. Or are they synthesized? Introns are a prevalent feature of eukaryotic genomes, yet their origins and contributions to genome function and evolution remain mysterious. An intron (for intragenic region) is any nucleotide sequence within a gene that is removed by RNA splicing during maturation of the final RNA product. Since they appear to have arisen very recently in evolution by sequence drift and do not appear to contribute to gene expression or its regulation, we call these protointrons. PLoS biology. Lamington (1951), Herculaneum (AD 79 Vesuvius eruption), and St. Pierre (1902 Mt. The dystrophin gene in the mdx mouse provides a favored system for study of exon skipping associated with nonsense mutations.  |  Some are found in non-coding RNAs (e. g. CUTs and SUTs), where they may contribute to the creation of new genes. This body of work has shown that mRNA-mediated duplication represents a widespread phenomenon that produces an array of new genes that contribute to organismal diversity and adaptation. Details of structural damage should be recorded and mapped around future eruptions in order to help refine this aspect of consequence analysis. The 'introns late' hypothesis counters that spliceosomal introns emerged only in eukaryotes, and moreover, have been inserted into protein-coding genes continuously throughout the evolution of eukaryotes. A 2-year-old female with Hb H disease, was found to have not only three α-globin genes. Clipboard, Search History, and several other advanced features are temporarily unavailable. (F) The novel, initially alternatively spliced exon now becomes constitutively spliced, while the exon downstream of it acquires a PTC and may start the process of intronization. 2003;300:1393. Resonances to a case in unrelated algae suggest such elements hold general answers to long-standing mysteries of intron evolution. Additionally, the interplay between splicing factors and cleavage/polyadenylation factors is theorized to also affect the formation of intragenic DNA double-stranded breaks thereby contributing to intron loss. The three major classes of intron are clearly of unequal antiquity. The systems for mRNA surveillance, capping, and cleavage/polyadenylation are proposed to play pivotal roles in the physical establishment and distribution of spliceosomal introns along a transcript. The regions preceding and following the coding regions (exons) are transcribed but not translated, and are called 5′ and 3′ UTRs. 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