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Maas ZL, Dowell RD. Internal and external normalization of nascent RNA sequencing run-on experiments. BMC Bioinformatics 2024; 25:19. [PMID: 38216877 PMCID: PMC10785432 DOI: 10.1186/s12859-023-05607-3] [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: 03/21/2023] [Accepted: 12/07/2023] [Indexed: 01/14/2024] Open
Abstract
In experiments with significant perturbations to transcription, nascent RNA sequencing protocols are dependent on external spike-ins for reliable normalization. Unlike in RNA-seq, these spike-ins are not standardized and, in many cases, depend on a run-on reaction that is assumed to have constant efficiency across samples. To assess the validity of this assumption, we analyze a large number of published nascent RNA spike-ins to quantify their variability across existing normalization methods. Furthermore, we develop a new biologically-informed Bayesian model to estimate the error in spike-in based normalization estimates, which we term Virtual Spike-In (VSI). We apply this method both to published external spike-ins as well as using reads at the [Formula: see text] end of long genes, building on prior work from Mahat (Mol Cell 62(1):63-78, 2016. https://doi.org/10.1016/j.molcel.2016.02.025 ) and Vihervaara (Nat Commun 8(1):255, 2017. https://doi.org/10.1038/s41467-017-00151-0 ). We find that spike-ins in existing nascent RNA experiments are typically under sequenced, with high variability between samples. Furthermore, we show that these high variability estimates can have significant downstream effects on analysis, complicating biological interpretations of results.
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Affiliation(s)
- Zachary L Maas
- Department of Computer Science, University of Colorado, Boulder, USA
- BioFrontiers Institute, University of Colorado, Boulder, USA
| | - Robin D Dowell
- Department of Computer Science, University of Colorado, Boulder, USA.
- BioFrontiers Institute, University of Colorado, Boulder, USA.
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, USA.
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Hunter S, Hendrix J, Freeman J, Dowell RD, Allen MA. Transcription dosage compensation does not occur in Down syndrome. BMC Biol 2023; 21:228. [PMID: 37946204 PMCID: PMC10636926 DOI: 10.1186/s12915-023-01700-4] [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: 02/06/2023] [Accepted: 09/12/2023] [Indexed: 11/12/2023] Open
Abstract
BACKGROUND The increase in DNA copy number in Down syndrome (DS; caused by trisomy 21) has led to the DNA dosage hypothesis, which posits that the level of gene expression is proportional to the gene's DNA copy number. Yet many reports have suggested that a proportion of chromosome 21 genes are dosage compensated back towards typical expression levels (1.0×). In contrast, other reports suggest that dosage compensation is not a common mechanism of gene regulation in trisomy 21, providing support to the DNA dosage hypothesis. RESULTS In our work, we use both simulated and real data to dissect the elements of differential expression analysis that can lead to the appearance of dosage compensation, even when compensation is demonstrably absent. Using lymphoblastoid cell lines derived from a family with an individual with Down syndrome, we demonstrate that dosage compensation is nearly absent at both nascent transcription (GRO-seq) and steady-state RNA (RNA-seq) levels. Furthermore, we link the limited apparent dosage compensation to expected allelic variation in transcription levels. CONCLUSIONS Transcription dosage compensation does not occur in Down syndrome. Simulated data containing no dosage compensation can appear to have dosage compensation when analyzed via standard methods. Moreover, some chromosome 21 genes that appear to be dosage compensated are consistent with allele specific expression.
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Affiliation(s)
- Samuel Hunter
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, 80301, USA
| | - Jo Hendrix
- BioFrontiers Institute, University of Colorado, Boulder, 80309, USA
- Computational Bioscience, The University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Center for Genes, Environment and Health, National Jewish Health, Denver, CO, USA
| | - Justin Freeman
- BioFrontiers Institute, University of Colorado, Boulder, 80309, USA
| | - Robin D Dowell
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, 80301, USA
- BioFrontiers Institute, University of Colorado, Boulder, 80309, USA
- Linda Crnic Institute for Down Syndrome, 80045, Aurora, USA
- Crnic Boulder Branch, BioFrontiers, Boulder, 80309, USA
| | - Mary A Allen
- BioFrontiers Institute, University of Colorado, Boulder, 80309, USA.
- Linda Crnic Institute for Down Syndrome, 80045, Aurora, USA.
- Crnic Boulder Branch, BioFrontiers, Boulder, 80309, USA.
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Pascal C, Zonszain J, Hameiri O, Gargi-Levi C, Lev-Maor G, Tammer L, Levy T, Tarabeih A, Roy VR, Ben-Salmon S, Elbaz L, Eid M, Hakim T, Abu Rabe'a S, Shalev N, Jordan A, Meshorer E, Ast G. Human histone H1 variants impact splicing outcome by controlling RNA polymerase II elongation. Mol Cell 2023; 83:3801-3817.e8. [PMID: 37922872 DOI: 10.1016/j.molcel.2023.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 08/17/2023] [Accepted: 10/05/2023] [Indexed: 11/07/2023]
Abstract
Histones shape chromatin structure and the epigenetic landscape. H1, the most diverse histone in the human genome, has 11 variants. Due to the high structural similarity between the H1s, their unique functions in transferring information from the chromatin to mRNA-processing machineries have remained elusive. Here, we generated human cell lines lacking up to five H1 subtypes, allowing us to characterize the genomic binding profiles of six H1 variants. Most H1s bind to specific sites, and binding depends on multiple factors, including GC content. The highly expressed H1.2 has a high affinity for exons, whereas H1.3 binds intronic sequences. H1s are major splicing regulators, especially of exon skipping and intron retention events, through their effects on the elongation of RNA polymerase II (RNAPII). Thus, H1 variants determine splicing fate by modulating RNAPII elongation.
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Affiliation(s)
- Corina Pascal
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Jonathan Zonszain
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ofir Hameiri
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Chen Gargi-Levi
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Galit Lev-Maor
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Luna Tammer
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tamar Levy
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Anan Tarabeih
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Vanessa Rachel Roy
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Stav Ben-Salmon
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Liraz Elbaz
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Mireille Eid
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tamar Hakim
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Salima Abu Rabe'a
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nana Shalev
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Albert Jordan
- Instituto de Biologia Molecular de Barcelona (IBMB-CSIC), Carrer de Baldiri Reixac, 15, 08028 Barcelona, Spain
| | - Eran Meshorer
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, Jerusalem 91904, Israel; Edmond and Lily Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Gil Ast
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
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Hunter S, Dowell RD, Hendrix J, Freeman J, Allen MA. Transcription dosage compensation does not occur in Down syndrome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.07.543933. [PMID: 37333218 PMCID: PMC10274774 DOI: 10.1101/2023.06.07.543933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Background Trisomy 21, also known as Down syndrome, describes the genetic condition of having an extra copy of chromosome 21. The increase in DNA copy number has led to the "DNA dosage hypothesis", which claims that the level of gene transcription is proportional to the gene's DNA copy number. Yet many reports have suggested that a proportion of chromosome 21 genes are dosage compensated back towards typical expression levels (1.0x). In contrast, other reports suggest that dosage compensation is not a common mechanism of gene regulation in Trisomy 21, providing support to the DNA dosage hypothesis. Results In our work, we use both simulated and real data to dissect the elements of differential expression analysis that can lead to the appearance of dosage compensation even when compensation is demonstrably absent. Using lymphoblastoid cell lines derived from a family of an individual with Down syndrome, we demonstrate that dosage compensation is nearly absent at both nascent transcription (GRO-seq) and steady-state RNA (RNA-seq) levels. Conclusions Transcriptional dosage compensation does not occur in Down syndrome. Simulated data containing no dosage compensation can appear to have dosage compensation when analyzed via standard methods. Moreover, some chromosome 21 genes that appear to be dosage compensated are consistent with allele specific expression.
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