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Kalita AI, Keller Valsecchi CI. Dosage compensation in non-model insects - progress and perspectives. Trends Genet 2024:S0168-9525(24)00207-5. [PMID: 39341686 DOI: 10.1016/j.tig.2024.08.010] [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: 05/06/2024] [Revised: 08/26/2024] [Accepted: 08/28/2024] [Indexed: 10/01/2024]
Abstract
In many multicellular eukaryotes, heteromorphic sex chromosomes are responsible for determining the sexual characteristics and reproductive functions of individuals. Sex chromosomes can cause a dosage imbalance between sexes, which in some species is re-equilibrated by dosage compensation (DC). Recent genomic advances have extended our understanding of DC mechanisms in insects beyond model organisms such as Drosophila melanogaster. We review current knowledge of insect DC, focusing on its conservation and divergence across orders, the evolutionary dynamics of neo-sex chromosomes, and the diversity of molecular mechanisms. We propose a framework to uncover DC regulators in non-model insects that relies on integrating evolutionary, genomic, and functional approaches. This comprehensive approach will facilitate a deeper understanding of the evolution and essentiality of gene regulatory mechanisms.
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Joy J, Fusari E, Milán M. Aneuploidy-induced cellular behaviors: Insights from Drosophila. Dev Cell 2024; 59:295-307. [PMID: 38320484 DOI: 10.1016/j.devcel.2023.12.009] [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: 02/02/2023] [Revised: 08/09/2023] [Accepted: 12/15/2023] [Indexed: 02/08/2024]
Abstract
A balanced gene complement is crucial for proper cell function. Aneuploidy, the condition of having an imbalanced chromosome set, alters the stoichiometry of gene copy numbers and protein complexes and has dramatic consequences at the cellular and organismal levels. In humans, aneuploidy is associated with different pathological conditions including cancer, microcephaly, mental retardation, miscarriages, and aging. Over the last century, Drosophila has provided a valuable system for studying the consequences of systemic aneuploidies. More recently, it has contributed to the identification and molecular dissection of aneuploidy-induced cellular behaviors and their impact at the tissue and organismal levels. In this perspective, we review this active field of research, first by comparing knowledge from yeast, mouse, and human cells, then by highlighting the contributions of Drosophila. The aim of these discussions was to further our understanding of the functional interplay between aneuploidy, cell physiology, and tissue homeostasis in human development and disease.
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Affiliation(s)
- Jery Joy
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10-12, 08028 Barcelona, Spain
| | - Elena Fusari
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10-12, 08028 Barcelona, Spain
| | - Marco Milán
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac, 10-12, 08028 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluis Companys, 23, 08010 Barcelona, Spain.
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Krzywinska E, Ribeca P, Ferretti L, Hammond A, Krzywinski J. A novel factor modulating X chromosome dosage compensation in Anopheles. Curr Biol 2023; 33:4697-4703.e4. [PMID: 37774706 DOI: 10.1016/j.cub.2023.09.001] [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] [Received: 07/03/2023] [Revised: 08/31/2023] [Accepted: 09/01/2023] [Indexed: 10/01/2023]
Abstract
Dosage compensation (DC), a process countering chromosomal imbalance in individuals with heteromorphic sex chromosomes, has been molecularly characterized only in mammals, Caenorhabditis elegans, and fruit flies.1 In Drosophila melanogaster males, it is achieved by an approximately 2-fold hypertranscription of the monosomic X chromosome mediated by the MSL complex.2,3 The complex is not assembled on female X chromosomes because production of its key protein MSL-2 is prevented due to intron retention and inhibition of translation by Sex-lethal, a female-specific protein operating at the top of the sex determination pathway.4 It remains unclear how DC is mechanistically regulated in other insects. In the malaria mosquito Anopheles gambiae, an approximately 2-fold hypertranscription of the male X also occurs5 by a yet-unknown molecular mechanism distinct from that in D. melanogaster.6 Here we show that a male-specifically spliced gene we call 007, which arose by a tandem duplication in the Anopheles ancestral lineage, is involved in the control of DC in males. Homozygous 007 knockouts lead to a global downregulation of the male X, phenotypically manifested by a slower development compared to wild-type mosquitoes or mutant females-however, without loss of viability or fertility. In females, a 007 intron retention promoted by the sex determination protein Femaleless, known to prevent hypertranscription from both X chromosomes,7 introduces a premature termination codon apparently rendering the female transcripts non-productive. In addition to providing a unique perspective on DC evolution, the 007, with its conserved properties, may represent an important addition to a genetic toolbox for malaria vector control.
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Affiliation(s)
| | - Paolo Ribeca
- The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK; National Infection Service, UK Health Security Agency, Colindale Avenue, London NW9 5EQ, UK
| | - Luca Ferretti
- Big Data Institute, Nuffield Department of Medicine, University of Oxford, Old Road Campus, Oxford OX3 7LF, UK
| | - Andrew Hammond
- Department of Life Sciences, Imperial College, Exhibition Road, London SW7 2AZ, UK; Biocentis, S.r.l., Via Mazzieri, 05100 Terni, Italy
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4
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Faucillion ML, Johansson AM, Larsson J. Modulation of RNA stability regulates gene expression in two opposite ways: through buffering of RNA levels upon global perturbations and by supporting adapted differential expression. Nucleic Acids Res 2022; 50:4372-4388. [PMID: 35390159 PMCID: PMC9071389 DOI: 10.1093/nar/gkac208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 03/09/2022] [Accepted: 03/17/2022] [Indexed: 01/02/2023] Open
Abstract
The steady state levels of RNAs, often referred to as expression levels, result from a well-balanced combination of RNA transcription and decay. Alterations in RNA levels will therefore result from tight regulation of transcription rates, decay rates or both. Here, we explore the role of RNA stability in achieving balanced gene expression and present genome-wide RNA stabilities in Drosophila melanogaster male and female cells as well as male cells depleted of proteins essential for dosage compensation. We identify two distinct RNA-stability mediated responses involved in regulation of gene expression. The first of these responds to acute and global changes in transcription and thus counteracts potentially harmful gene mis-expression by shifting the RNA stability in the direction opposite to the transcriptional change. The second response enhances inter-individual differential gene expression by adjusting the RNA stability in the same direction as a transcriptional change. Both mechanisms are global, act on housekeeping as well as non-housekeeping genes and were observed in both flies and mammals. Additionally, we show that, in contrast to mammals, modulation of RNA stability does not detectably contribute to dosage compensation of the sex-chromosomes in D. melanogaster.
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Affiliation(s)
| | | | - Jan Larsson
- Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden
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5
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Complex Genetic Interactions between Piwi and HP1a in the Repression of Transposable Elements and Tissue-Specific Genes in the Ovarian Germline. Int J Mol Sci 2021; 22:ijms222413430. [PMID: 34948223 PMCID: PMC8707237 DOI: 10.3390/ijms222413430] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/03/2021] [Accepted: 12/10/2021] [Indexed: 11/16/2022] Open
Abstract
Insertions of transposable elements (TEs) in eukaryotic genomes are usually associated with repressive chromatin, which spreads to neighbouring genomic sequences. In ovaries of Drosophila melanogaster, the Piwi-piRNA pathway plays a key role in the transcriptional silencing of TEs considered to be exerted mostly through the establishment of H3K9me3 histone marks recruiting Heterochromatin Protein 1a (HP1a). Here, using RNA-seq, we investigated the expression of TEs and the adjacent genomic regions upon Piwi and HP1a germline knockdowns sharing a similar genetic background. We found that the depletion of Piwi and HP1a led to the derepression of only partially overlapping TE sets. Several TEs were silenced predominantly by HP1a, whereas the upregulation of some other TEs was more pronounced upon Piwi knockdown and, surprisingly, was diminished upon a Piwi/HP1a double-knockdown. We revealed that HP1a loss influenced the expression of thousands of protein-coding genes mostly not adjacent to TE insertions and, in particular, downregulated a putative transcriptional factor required for TE activation. Nevertheless, our results indicate that Piwi and HP1a cooperatively exert repressive effects on the transcription of euchromatic loci flanking the insertions of some Piwi-regulated TEs. We suggest that this mechanism controls the silencing of a small set of TE-adjacent tissue-specific genes, preventing their inappropriate expression in ovaries.
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When Down Is Up: Heterochromatin, Nuclear Organization and X Upregulation. Cells 2021; 10:cells10123416. [PMID: 34943924 PMCID: PMC8700316 DOI: 10.3390/cells10123416] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 11/29/2021] [Accepted: 12/01/2021] [Indexed: 12/21/2022] Open
Abstract
Organisms with highly differentiated sex chromosomes face an imbalance in X-linked gene dosage. Male Drosophila solve this problem by increasing expression from virtually every gene on their single X chromosome, a process known as dosage compensation. This involves a ribonucleoprotein complex that is recruited to active, X-linked genes to remodel chromatin and increase expression. Interestingly, the male X chromosome is also enriched for several proteins associated with heterochromatin. Furthermore, the polytenized male X is selectively disrupted by the loss of factors involved in repression, silencing, heterochromatin formation or chromatin remodeling. Mutations in many of these factors preferentially reduce male survival or enhance the lethality of mutations that prevent normal recognition of the X chromosome. The involvement of primarily repressive factors in a process that elevates expression has long been puzzling. Interestingly, recent work suggests that the siRNA pathway, often associated with heterochromatin formation and repression, also helps the dosage compensation machinery identify the X chromosome. In light of this finding, we revisit the evidence that links nuclear organization and heterochromatin to regulation of the male X chromosome.
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Conditional knockdown of transformer in sheep blow fly suggests a role in repression of dosage compensation and potential for population suppression. PLoS Genet 2021; 17:e1009792. [PMID: 34662332 PMCID: PMC8553175 DOI: 10.1371/journal.pgen.1009792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 10/28/2021] [Accepted: 08/24/2021] [Indexed: 11/19/2022] Open
Abstract
The transformer (tra) gene is essential for female development in many insect species, including the Australian sheep blow fly, Lucilia cuprina. Sex-specific tra RNA splicing is controlled by Sex lethal (Sxl) in Drosophila melanogaster but is auto-regulated in L. cuprina. Sxl also represses X chromosome dosage compensation in female D. melanogaster. We have developed conditional Lctra RNAi knockdown strains using the tet-off system. Four strains did not produce females on diet without tetracycline and could potentially be used for genetic control of L. cuprina. In one strain, which showed both maternal and zygotic tTA expression, most XX transformed males died at the pupal stage. RNAseq and qRT-PCR analyses of mid-stage pupae showed increased expression of X-linked genes in XX individuals. These results suggest that Lctra promotes somatic sexual differentiation and inhibits X chromosome dosage compensation in female L. cuprina. However, XX flies homozygous for a loss-of-function Lctra knockin mutation were fully transformed and showed high pupal eclosion. Two of five X-linked genes examined showed a significant increase in mRNA levels in XX males. The stronger phenotype in the RNAi knockdown strain could indicate that maternal Lctra expression may be essential for initiation of dosage compensation suppression in female embryos.
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Lindehell H, Glotov A, Dorafshan E, Schwartz YB, Larsson J. The role of H3K36 methylation and associated methyltransferases in chromosome-specific gene regulation. SCIENCE ADVANCES 2021; 7:eabh4390. [PMID: 34597135 PMCID: PMC10938550 DOI: 10.1126/sciadv.abh4390] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
In Drosophila, two chromosomes require special mechanisms to balance their transcriptional output to the rest of the genome. These are the male-specific lethal complex targeting the male X chromosome and Painting of fourth targeting chromosome 4. Here, we explore the role of histone H3 methylated at lysine-36 (H3K36) and the associated methyltransferases—Set2, NSD, and Ash1—in these two chromosome-specific systems. We show that the loss of Set2 impairs the MSL complex–mediated dosage compensation; however, the effect is not recapitulated by H3K36 replacement and indicates an alternative target of Set2. Unexpectedly, balanced transcriptional output from the fourth chromosome requires intact H3K36 and depends on the additive functions of NSD and Ash1. We conclude that H3K36 methylation and the associated methyltransferases are important factors to balance transcriptional output of the male X chromosome and the fourth chromosome. Furthermore, our study highlights the pleiotropic effects of these enzymes.
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Affiliation(s)
- Henrik Lindehell
- Department of Molecular Biology, Umeå University, SE-90187 Umeå, Sweden
| | - Alexander Glotov
- Department of Molecular Biology, Umeå University, SE-90187 Umeå, Sweden
| | - Eshagh Dorafshan
- Department of Molecular Biology, Umeå University, SE-90187 Umeå, Sweden
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Casale AM, Cappucci U, Piacentini L. Unravelling HP1 functions: post-transcriptional regulation of stem cell fate. Chromosoma 2021; 130:103-111. [PMID: 34128099 PMCID: PMC8426308 DOI: 10.1007/s00412-021-00760-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 05/17/2021] [Accepted: 06/01/2021] [Indexed: 12/20/2022]
Abstract
Heterochromatin protein 1 (HP1) is a non-histone chromosomal protein first identified in Drosophila as a major component of constitutive heterochromatin, required for stable epigenetic gene silencing in many species including humans. Over the years, several studies have highlighted additional roles of HP1 in different cellular processes including telomere maintenance, DNA replication and repair, chromosome segregation and, surprisingly, positive regulation of gene expression. In this review, we briefly summarize past research and recent results supporting the unexpected and emerging role of HP1 in activating gene expression. In particular, we discuss the role of HP1 in post-transcriptional regulation of mRNA processing because it has proved decisive in the control of germline stem cells homeostasis in Drosophila and has certainly added a new dimension to our understanding on HP1 targeting and functions in epigenetic regulation of stem cell behaviour.
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Affiliation(s)
- Assunta Maria Casale
- Department of Biology and Biotechnology "C. Darwin", Sapienza University of Rome, Rome, Italy.
| | - Ugo Cappucci
- Department of Biology and Biotechnology "C. Darwin", Sapienza University of Rome, Rome, Italy
| | - Lucia Piacentini
- Department of Biology and Biotechnology "C. Darwin", Sapienza University of Rome, Rome, Italy.
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10
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Ekhteraei-Tousi S, Lewerentz J, Larsson J. Painting of Fourth and the X-Linked 1.688 Satellite in D. melanogaster is Involved in Chromosome-Wide Gene Regulation. Cells 2020; 9:cells9020323. [PMID: 32019091 PMCID: PMC7072490 DOI: 10.3390/cells9020323] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 01/23/2020] [Accepted: 01/28/2020] [Indexed: 01/01/2023] Open
Abstract
Chromosome-specific regulatory mechanisms provide a model to understand the coordinated regulation of genes on entire chromosomes or on larger genomic regions. In fruit flies, two chromosome-wide systems have been characterized: The male-specific lethal (MSL) complex, which mediates dosage compensation and primarily acts on the male X-chromosome, and Painting of fourth (POF), which governs chromosome-specific regulation of genes located on the 4th chromosome. How targeting of one specific chromosome evolves is still not understood; but repeated sequences, in forms of satellites and transposable elements, are thought to facilitate the evolution of chromosome-specific targeting. The highly repetitive 1.688 satellite has been functionally connected to both these systems. Considering the rapid evolution and the necessarily constant adaptation of regulatory mechanisms, such as dosage compensation, we hypothesised that POF and/or 1.688 may still show traces of dosage-compensation functions. Here, we test this hypothesis by transcriptome analysis. We show that loss of Pof decreases not only chromosome 4 expression but also reduces the X-chromosome expression in males. The 1.688 repeat deletion, Zhr1 (Zygotic hybrid rescue), does not affect male dosage compensation detectably; however, Zhr1 in females causes a stimulatory effect on X-linked genes with a strong binding affinity to the MSL complex (genes close to high-affinity sites). Lack of pericentromeric 1.688 also affected 1.688 expression in trans and was linked to the differential expression of genes involved in eggshell formation. We discuss our results with reference to the connections between POF, the 1.688 satellite and dosage compensation, and the role of the 1.688 satellite in hybrid lethality.
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11
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Meisel RP, Delclos PJ, Wexler JR. The X chromosome of the German cockroach, Blattella germanica, is homologous to a fly X chromosome despite 400 million years divergence. BMC Biol 2019; 17:100. [PMID: 31806031 PMCID: PMC6894488 DOI: 10.1186/s12915-019-0721-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 11/11/2019] [Indexed: 12/30/2022] Open
Abstract
Background Sex chromosome evolution is a dynamic process that can proceed at varying rates across lineages. For example, different chromosomes can be sex-linked between closely related species, whereas other sex chromosomes have been conserved for > 100 million years. Cases of long-term sex chromosome conservation could be informative of factors that constrain sex chromosome evolution. Cytological similarities between the X chromosomes of the German cockroach (Blattella germanica) and most flies suggest that they may be homologous—possibly representing an extreme case of long-term conservation. Results To test the hypothesis that the cockroach and fly X chromosomes are homologous, we analyzed whole-genome sequence data from cockroaches. We found evidence in both sequencing coverage and heterozygosity that a significant excess of the same genes are on both the cockroach and fly X chromosomes. We also present evidence that the candidate X-linked cockroach genes may be dosage compensated in hemizygous males. Consistent with this hypothesis, three regulators of transcription and chromatin on the fly X chromosome are conserved in the cockroach genome. Conclusions Our results support our hypothesis that the German cockroach shares the same X chromosome as most flies. This may represent the convergent evolution of the X chromosome in the lineages leading to cockroaches and flies. Alternatively, the common ancestor of most insects may have had an X chromosome that resembled the extant cockroach and fly X. Cockroaches and flies diverged ∼ 400 million years ago, which would be the longest documented conservation of a sex chromosome. Cockroaches and flies have different mechanisms of sex determination, raising the possibility that the X chromosome was conserved despite the evolution of the sex determination pathway.
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Affiliation(s)
- Richard P Meisel
- Department of Biology and Biochemistry, University of Houston, 3455 Cullen Blvd., Houston, 77204, TX, USA.
| | - Pablo J Delclos
- Department of Biology and Biochemistry, University of Houston, 3455 Cullen Blvd., Houston, 77204, TX, USA
| | - Judith R Wexler
- Department of Ecology and Evolution, University of California, Davis, One Shields Ave, Davis, 95616, CA, USA.,Department of Entomology, University of Maryland, 4112 Plant Sciences Building, College Park, 20742, MD, USA
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12
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Abstract
Aneuploidy (i.e., abnormal chromosome number) is the leading cause of miscarriage and congenital defects in humans. Moreover, aneuploidy is ubiquitous in cancer. The deleterious phenotypes associated with aneuploidy are likely a result of the imbalance in the levels of gene products derived from the additional chromosome(s). Here, we summarize the current knowledge on how the presence of extra chromosomes impacts gene expression. We describe studies that have found a strict correlation between gene dosage and transcript levels as wells as studies that have found a less stringent correlation, hinting at the possible existence of dosage compensation mechanisms. We conclude by peering into the epigenetic changes found in aneuploid cells and outlining current knowledge gaps and potential areas of future investigation.
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Affiliation(s)
- Shihoko Kojima
- Department of Biological Sciences & Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA 24061, USA
| | - Daniela Cimini
- Department of Biological Sciences & Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA 24061, USA
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Sidorenko DS, Sidorenko IA, Zykova TY, Goncharov FP, Larsson J, Zhimulev IF. Molecular and genetic organization of bands and interbands in the dot chromosome of Drosophila melanogaster. Chromosoma 2019; 128:97-117. [PMID: 31041520 PMCID: PMC6536484 DOI: 10.1007/s00412-019-00703-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 01/09/2019] [Accepted: 04/02/2019] [Indexed: 12/24/2022]
Abstract
The fourth chromosome smallest in the genome of Drosophila melanogaster differs from other chromosomes in many ways. It has high repeat density in conditions of a large number of active genes. Gray bands represent a significant part of this polytene chromosome. Specific proteins including HP1a, POF, and dSETDB1 establish the epigenetic state of this unique chromatin domain. In order to compare maps of localization of genes, bands, and chromatin types of the fourth chromosome, we performed FISH analysis of 38 probes chosen according to the model of four chromatin types. It allowed clarifying the dot chromosome cytological map consisting of 16 loose gray bands, 11 dense black bands, and 26 interbands. We described the relation between chromatin states and bands. Open aquamarine chromatin mostly corresponds to interbands and it contains 5'UTRs of housekeeping genes. Their coding parts are embedded in gray bands substantially composed of lazurite chromatin of intermediate compaction. Polygenic black bands contain most of dense ruby chromatin, and also some malachite and lazurite. Having an accurate map of the fourth chromosome bands and its correspondence to physical map, we found that DNase I hypersensitivity sites, ORC2 protein, and P-elements are mainly located in open aquamarine chromatin, while element 1360, characteristic of the fourth chromosome, occupies band chromatin types. POF and HP1a proteins providing special organization of this chromosome are mostly located in aquamarine and lazurite chromatin. In general, band organization of the fourth chromosome shares the features of the whole Drosophila genome.
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Affiliation(s)
- Darya S Sidorenko
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Lavrentiev Ave. 8/2, Novosibirsk, Russia, 630090
| | - Ivan A Sidorenko
- Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Tatyana Yu Zykova
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Lavrentiev Ave. 8/2, Novosibirsk, Russia, 630090
| | - Fedor P Goncharov
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Lavrentiev Ave. 8/2, Novosibirsk, Russia, 630090
| | - Jan Larsson
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology of the Siberian Branch of the Russian Academy of Sciences, Lavrentiev Ave. 8/2, Novosibirsk, Russia, 630090. .,Laboratory of structural, functional and comparative genomics of the Novosibirsk State University, Novosibirsk, Russia.
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14
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Sidorenko DS, Zykova TY, Khoroshko VA, Pokholkova GV, Demakov SA, Larsson J, Belyaeva ES, Zhimulev IF. Polytene chromosomes reflect functional organization of the Drosophila genome. Vavilovskii Zhurnal Genet Selektsii 2019. [DOI: 10.18699/vj19.474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Polytene chromosomes of Drosophila melanogaster are a convenient model for studying interphase chromosomes of eukaryotes. They are giant in size in comparison with diploid cell chromosomes and have a pattern of cross stripes resulting from the ordered chromatid arrangement. Each region of polytene chromosomes has a unique banding pattern. Using the model of four chromatin types that reveals domains of varying compaction degrees, we were able to correlate the physical and cytological maps of some polytene chromosome regions and to show the main properties of genetic and molecular organization of bands and interbands, that we describe in this review. On the molecular map of the genome, the interbands correspond to decompacted aquamarine chromatin and 5’ ends of ubiquitously active genes. Gray bands contain lazurite and malachite chromatin, intermediate in the level of compaction, and, mainly, coding parts of genes. Dense black transcriptionally inactive bands are enriched in ruby chromatin. Localization of several dozens of interbands on the genome molecular map allowed us to study in detail their architecture according to the data of whole genome projects. The distribution of proteins and regulatory elements of the genome in the promoter regions of genes localized in the interbands shows that these parts of interbands are probably responsible for the formation of open chromatin that is visualized in polytene chromosomes as interbands. Thus, the permanent genetic activity of interbands and gray bands and the inactivity of genes in black bands are the basis of the universal banding pattern in the chromosomes of all Drosophila tissues. The smallest fourth chromosome of Drosophila with an atypical protein composition of chromatin is a special case. Using the model of four chromatin states and fluorescent in situ hybridization, its cytological map was refined and the genomic coordinates of all bands and interbands were determined. It was shown that, in spite of the peculiarities of this chromosome, its band organization in general corresponds to the rest of the genome. Extremely long genes of different Drosophila chromosomes do not fit the common scheme, since they can occupy a series of alternating bands and interbands (up to nine chromosomal structures) formed by parts of these genes.
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Affiliation(s)
| | | | | | | | | | - J. Larsson
- Department of Molecular Biology, Umea University
| | | | - I. F. Zhimulev
- Institute of Molecular and Cellular Biology, SB RAS; 3 Laboratory of Structural, Functional and Comparative Genomics of the Novosibirsk State University
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15
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Chunduri NK, Storchová Z. The diverse consequences of aneuploidy. Nat Cell Biol 2019; 21:54-62. [PMID: 30602769 DOI: 10.1038/s41556-018-0243-8] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 10/31/2018] [Indexed: 12/25/2022]
Abstract
Aneuploidy, or imbalanced chromosome number, has profound effects on eukaryotic cells. In humans, aneuploidy is associated with various pathologies, including cancer, which suggests that it mediates a proliferative advantage under these conditions. Here, we discuss physiological changes triggered by aneuploidy, such as altered cell growth, transcriptional changes, proteotoxic stress, genomic instability and response to interferons, and how cancer cells adapt to the changing aneuploid genome.
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Affiliation(s)
| | - Zuzana Storchová
- Department of Molecular Genetics, TU Kaiserslautern, Kaiserslautern, Germany.
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16
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Kim M, Faucillion ML, Larsson J. RNA-on-X 1 and 2 in Drosophila melanogaster fulfill separate functions in dosage compensation. PLoS Genet 2018; 14:e1007842. [PMID: 30532158 PMCID: PMC6301720 DOI: 10.1371/journal.pgen.1007842] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 12/20/2018] [Accepted: 11/20/2018] [Indexed: 02/03/2023] Open
Abstract
In Drosophila melanogaster, the male-specific lethal (MSL) complex plays a key role in dosage compensation by stimulating expression of male X-chromosome genes. It consists of MSL proteins and two long noncoding RNAs, roX1 and roX2, that are required for spreading of the complex on the chromosome and are redundant in the sense that loss of either does not affect male viability. However, despite rapid evolution, both roX species are present in diverse Drosophilidae species, raising doubts about their full functional redundancy. Thus, we have investigated consequences of deleting roX1 and/or roX2 to probe their specific roles and redundancies in D. melanogaster. We have created a new mutant allele of roX2 and show that roX1 and roX2 have partly separable functions in dosage compensation. In larvae, roX1 is the most abundant variant and the only variant present in the MSL complex when the complex is transmitted (physically associated with the X-chromosome) in mitosis. Loss of roX1 results in reduced expression of the genes on the X-chromosome, while loss of roX2 leads to MSL-independent upregulation of genes with male-biased testis-specific transcription. In roX1 roX2 mutant, gene expression is strongly reduced in a manner that is not related to proximity to high-affinity sites. Our results suggest that high tolerance of mis-expression of the X-chromosome has evolved. We propose that this may be a common property of sex-chromosomes, that dosage compensation is a stochastic process and its precision for each individual gene is regulated by the density of high-affinity sites in the locus.
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Affiliation(s)
- Maria Kim
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | | | - Jan Larsson
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- * E-mail:
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Benhra N, Barrio L, Muzzopappa M, Milán M. Chromosomal Instability Induces Cellular Invasion in Epithelial Tissues. Dev Cell 2018; 47:161-174.e4. [DOI: 10.1016/j.devcel.2018.08.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 06/19/2018] [Accepted: 08/22/2018] [Indexed: 01/08/2023]
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Davis RJ, Belikoff EJ, Scholl EH, Li F, Scott MJ. no blokes Is Essential for Male Viability and X Chromosome Gene Expression in the Australian Sheep Blowfly. Curr Biol 2018; 28:1987-1992.e3. [PMID: 29887311 DOI: 10.1016/j.cub.2018.05.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/19/2018] [Accepted: 05/02/2018] [Indexed: 12/30/2022]
Abstract
It has been hypothesized that the Drosophila 4th chromosome is derived from an ancient X chromosome [1]. In the Australian sheep blowfly, Lucilia cuprina, the heterochromatic X chromosome contains few active genes and orthologs of Drosophila X-linked genes are autosomal. Of 8 X-linked genes identified previously in L. cuprina, 6 were orthologs of Drosophila 4th-chromosome genes [2]. The X-linked genes were expressed equally in males and females. Here we identify an additional 51 X-linked genes and show that most are dosage compensated. Orthologs of 49 of the 59 X-linked genes are on the 4th chromosome in D. melanogaster. Because painting of fourth (Pof) is important for expression of Drosophila 4th-chromosome genes [3], we used Cas9 to make a loss-of-function knockin mutation in an L. cuprina Pof ortholog we call no blokes (nbl). Homozygous nbl males derived from homozygous nbl mothers die at the late pupal stage. Homozygous nbl females are viable, fertile, and live longer than heterozygous nbl females. RNA expression of most X-linked genes was reduced in homozygous nbl male pupae and to a lesser extent in nbl females compared to heterozygous siblings. The results suggest that NBL could be important for X chromosome dosage compensation in L. cuprina. NBL may also facilitate gene expression in the heterochromatic environment of the X chromosome in both sexes. This study supports the hypothesis on the origin of the Drosophila 4th chromosome and that a POF-like protein was required for normal gene expression on the ancient X chromosome.
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Affiliation(s)
- Rebecca J Davis
- Department of Entomology and Plant Pathology, North Carolina State University, Campus Box 7613, Raleigh, NC 27695-7613, USA
| | - Esther J Belikoff
- Department of Entomology and Plant Pathology, North Carolina State University, Campus Box 7613, Raleigh, NC 27695-7613, USA
| | - Elizabeth H Scholl
- Bioinformatics Research Center, North Carolina State University, Campus Box 7566, Raleigh, NC 27695-7566, USA
| | - Fang Li
- Department of Entomology and Plant Pathology, North Carolina State University, Campus Box 7613, Raleigh, NC 27695-7613, USA
| | - Maxwell J Scott
- Department of Entomology and Plant Pathology, North Carolina State University, Campus Box 7613, Raleigh, NC 27695-7613, USA.
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The X-linked 1.688 Satellite in Drosophila melanogaster Promotes Specific Targeting by Painting of Fourth. Genetics 2017; 208:623-632. [PMID: 29242291 PMCID: PMC5788526 DOI: 10.1534/genetics.117.300581] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 12/10/2017] [Indexed: 11/18/2022] Open
Abstract
Repetitive DNA, represented by transposons and satellite DNA, constitutes a large portion of eukaryotic genomes, being the major component of constitutive heterochromatin. There is a growing body of evidence that it regulates several nuclear functions including chromatin state and the proper functioning of centromeres and telomeres. The 1.688 satellite is one of the most abundant repetitive sequences in Drosophila melanogaster, with the longest array being located in the pericentromeric region of the X-chromosome. Short arrays of 1.688 repeats are widespread within the euchromatic part of the X-chromosome, and these arrays were recently suggested to assist in recognition of the X-chromosome by the dosage compensation male-specific lethal complex. We discovered that a short array of 1.688 satellite repeats is essential for recruitment of the protein POF to a previously described site on the X-chromosome (PoX2) and to various transgenic constructs. On an isolated target, i.e., an autosomic transgene consisting of a gene upstream of 1.688 satellite repeats, POF is recruited to the transgene in both males and females. The sequence of the satellite, as well as its length and position within the recruitment element, are the major determinants of targeting. Moreover, the 1.688 array promotes POF targeting to the roX1-proximal PoX1 site in trans Finally, binding of POF to the 1.688-related satellite-enriched sequences is conserved in evolution. We hypothesize that the 1.688 satellite functioned in an ancient dosage compensation system involving POF targeting to the X-chromosome.
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Linger RJ, Belikoff EJ, Scott MJ. Dosage Compensation of X-Linked Muller Element F Genes but Not X-Linked Transgenes in the Australian Sheep Blowfly. PLoS One 2015; 10:e0141544. [PMID: 26506426 PMCID: PMC4624761 DOI: 10.1371/journal.pone.0141544] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/10/2015] [Indexed: 11/25/2022] Open
Abstract
In most animals that have X and Y sex chromosomes, chromosome-wide mechanisms are used to balance X-linked gene expression in males and females. In the fly Drosophila melanogaster, the dosage compensation mechanism also generally extends to X-linked transgenes. Over 70 transgenic lines of the Australian sheep blowfly Lucilia cuprina have been made as part of an effort to develop male-only strains for a genetic control program of this major pest of sheep. All lines carry a constitutively expressed fluorescent protein marker gene. In all 12 X-linked lines, female larvae show brighter fluorescence than male larvae, suggesting the marker gene is not dosage compensated. This has been confirmed by quantitative RT-PCR for selected lines. To determine if endogenous X-linked genes are dosage compensated, we isolated 8 genes that are orthologs of genes that are on the fourth chromosome in D. melanogaster. Recent evidence suggests that the D. melanogaster fourth chromosome, or Muller element F, is the ancestral X chromosome in Diptera that has reverted to an autosome in Drosophila species. We show by quantitative PCR of male and female DNA that 6 of the 8 linkage group F genes reside on the X chromosome in L. cuprina. The other two Muller element F genes were found to be autosomal in L. cuprina, whereas two Muller element B genes were found on the same region of the X chromosome as the L. cuprina orthologs of the D. melanogaster Ephrin and gawky genes. We find that the L. cuprina X chromosome genes are equally expressed in males and females (i.e., fully dosage compensated). Thus, unlike in Drosophila, it appears that the Lucilia dosage compensation system is specific for genes endogenous to the X chromosome and cannot be co-opted by recently arrived transgenes.
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Affiliation(s)
- Rebecca J. Linger
- Department of Entomology, North Carolina State University, Campus Box 7613, Raleigh, NC, 27695–7613, United States of America
| | - Esther J. Belikoff
- Department of Entomology, North Carolina State University, Campus Box 7613, Raleigh, NC, 27695–7613, United States of America
| | - Maxwell J. Scott
- Department of Entomology, North Carolina State University, Campus Box 7613, Raleigh, NC, 27695–7613, United States of America
- * E-mail:
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X Chromosome and Autosome Dosage Responses in Drosophila melanogaster Heads. G3-GENES GENOMES GENETICS 2015; 5:1057-63. [PMID: 25850426 PMCID: PMC4478536 DOI: 10.1534/g3.115.017632] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
X chromosome dosage compensation is required for male viability in Drosophila. Dosage compensation relative to autosomes is two-fold, but this is likely to be due to a combination of homeostatic gene-by-gene regulation and chromosome-wide regulation. We have baseline values for gene-by-gene dosage compensation on autosomes, but not for the X chromosome. Given the evolutionary history of sex chromosomes, these baseline values could differ. We used a series of deficiencies on the X and autosomes, along with mutations in the sex-determination gene transformer-2, to carefully measure the sex-independent X-chromosome response to gene dosage in adult heads by RNA sequencing. We observed modest and indistinguishable dosage compensation for both X chromosome and autosome genes, suggesting that the X chromosome is neither inherently more robust nor sensitive to dosage change.
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Proximity ligation assays of protein and RNA interactions in the male-specific lethal complex on Drosophila melanogaster polytene chromosomes. Chromosoma 2015; 124:385-95. [PMID: 25694028 PMCID: PMC4548014 DOI: 10.1007/s00412-015-0509-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 01/16/2015] [Accepted: 02/05/2015] [Indexed: 01/18/2023]
Abstract
In Drosophila, the male-specific lethal (MSL) complex specifically targets the male X chromosome and participates in a twofold increase in expression output leading to functional dosage compensation. The complex includes five proteins and two non-coding RNAs (ncRNAs). A number of additional associated factors have also been identified. However, the components’ roles and interactions have not been fully elucidated. The in situ proximity ligation assay (PLA) provides a sensitive means to determine whether proteins and other factors have bound to chromosomes in close proximity to each other, and thus may interact. Thus, we modified, tested, and applied the assay to probe interactions of MSL complex components on polytene chromosomes. We show that in situ PLA can detect and map both protein-protein and protein-ncRNA interactions on polytene chromosomes at high resolution. We further show that all five protein components of the MSL complex are in close proximity to each other, and the ncRNAs roX1 and roX2 bind the complex in close proximity to MLE. Our results also indicate that JIL1, a histone H3 Ser10 kinase enriched on the male X chromosome, interacts with MSL1 and MSL2, but not MSL3 of the MSL complex. In addition, we corroborate proposed interactions of the MSL complex with both CLAMP and TopoII.
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Figueiredo MLA, Kim M, Philip P, Allgardsson A, Stenberg P, Larsson J. Non-coding roX RNAs prevent the binding of the MSL-complex to heterochromatic regions. PLoS Genet 2014; 10:e1004865. [PMID: 25501352 PMCID: PMC4263465 DOI: 10.1371/journal.pgen.1004865] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 10/30/2014] [Indexed: 12/29/2022] Open
Abstract
Long non-coding RNAs contribute to dosage compensation in both mammals and Drosophila by inducing changes in the chromatin structure of the X-chromosome. In Drosophila melanogaster, roX1 and roX2 are long non-coding RNAs that together with proteins form the male-specific lethal (MSL) complex, which coats the entire male X-chromosome and mediates dosage compensation by increasing its transcriptional output. Studies on polytene chromosomes have demonstrated that when both roX1 and roX2 are absent, the MSL-complex becomes less abundant on the male X-chromosome and is relocated to the chromocenter and the 4th chromosome. Here we address the role of roX RNAs in MSL-complex targeting and the evolution of dosage compensation in Drosophila. We performed ChIP-seq experiments which showed that MSL-complex recruitment to high affinity sites (HAS) on the X-chromosome is independent of roX and that the HAS sequence motif is conserved in D. simulans. Additionally, a complete and enzymatically active MSL-complex is recruited to six specific genes on the 4th chromosome. Interestingly, our sequence analysis showed that in the absence of roX RNAs, the MSL-complex has an affinity for regions enriched in Hoppel transposable elements and repeats in general. We hypothesize that roX mutants reveal the ancient targeting of the MSL-complex and propose that the role of roX RNAs is to prevent the binding of the MSL-complex to heterochromatin. In both fruit flies and humans, males and females have different sets of sex chromosomes. This generates differences in gene dosage that must be compensated for by adjusting the transcriptional output of most genes located on the X-chromosome. The specific recognition and targeting of the X-chromosome is essential for such dosage compensation. In fruit flies, dosage compensation is mediated by the male-specific lethal (MSL) complex, which upregulates gene transcription on the male X-chromosome. The MSL-complex consists of five proteins and two non-coding RNAs, roX1 and roX2. While non-coding RNAs are known to be critical for dosage compensation in both flies and mammals, their precise functions remain elusive. Here we present a study on the targeting and function of the MSL-complex in the absence of roX RNAs. The results obtained suggest that the dosage compensating MSL-complex has an intrinsic tendency to target repeat-rich regions and that the function of roX RNAs is to prevent its binding to such targets. Our findings reveal an ancient targeting and regulatory function of the MSL-complex that has been adapted for use in dosage compensation and modified by the rapidly evolving noncoding roX RNAs.
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Affiliation(s)
| | - Maria Kim
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Philge Philip
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Computational Life Science Cluster (CLiC), Umeå University, Umeå, Sweden
| | | | - Per Stenberg
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Computational Life Science Cluster (CLiC), Umeå University, Umeå, Sweden
| | - Jan Larsson
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- * E-mail:
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24
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Johansson AM, Larsson J. Genome-wide mapping of Painting of fourth on Drosophila melanogaster salivary gland polytene chromosomes. GENOMICS DATA 2014; 2:63-5. [PMID: 26484072 PMCID: PMC4536025 DOI: 10.1016/j.gdata.2014.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 04/17/2014] [Indexed: 11/16/2022]
Abstract
The protein Painting of fourth (POF) in Drosophila melanogaster specifically targets and stimulates expression output from the heterochromatic 4th chromosome, thereby representing an autosome specific protein [[1], [2]]. Despite the high specificity for chromosome 4 genes, POF is occasionally observed binding to the cytological region 2L:31 in males and females [3] and two loci on the X-chromosome, PoX1 and PoX2 only in females [4]. Here we provide a detailed description of the experimental design and analysis of the tiling array data presented by Lundberg and colleagues in G3: Genes, Genomes, Genetics 2013 [4], where the female specific POF binding to PoX1 and PoX2 loci on the X chromosome was reported. We show the genome-wide high resolution binding profile of the POF protein where these different POF binding sites are detected. The complete data set is available at http://www.ncbi.nlm.nih.gov/geo/ (accession: GSE45402)
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Lee H, McManus CJ, Cho DY, Eaton M, Renda F, Somma MP, Cherbas L, May G, Powell S, Zhang D, Zhan L, Resch A, Andrews J, Celniker SE, Cherbas P, Przytycka TM, Gatti M, Oliver B, Graveley B, MacAlpine D. DNA copy number evolution in Drosophila cell lines. Genome Biol 2014; 15:R70. [PMID: 25262759 PMCID: PMC4289277 DOI: 10.1186/gb-2014-15-8-r70] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 07/01/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Structural rearrangements of the genome resulting in genic imbalance due to copy number change are often deleterious at the organismal level, but are common in immortalized cell lines and tumors, where they may be an advantage to cells. In order to explore the biological consequences of copy number changes in the Drosophila genome, we resequenced the genomes of 19 tissue-culture cell lines and generated RNA-Seq profiles. RESULTS Our work revealed dramatic duplications and deletions in all cell lines. We found three lines of evidence indicating that copy number changes were due to selection during tissue culture. First, we found that copy numbers correlated to maintain stoichiometric balance in protein complexes and biochemical pathways, consistent with the gene balance hypothesis. Second, while most copy number changes were cell line-specific, we identified some copy number changes shared by many of the independent cell lines. These included dramatic recurrence of increased copy number of the PDGF/VEGF receptor, which is also over-expressed in many cancer cells, and of bantam, an anti-apoptosis miRNA. Third, even when copy number changes seemed distinct between lines, there was strong evidence that they supported a common phenotypic outcome. For example, we found that proto-oncogenes were over-represented in one cell line (S2-DRSC), whereas tumor suppressor genes were under-represented in another (Kc167). CONCLUSION Our study illustrates how genome structure changes may contribute to selection of cell lines in vitro. This has implications for other cell-level natural selection progressions, including tumorigenesis.
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Affiliation(s)
- Hangnoh Lee
- />National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, 50 South Drive, Bethesda, MD 20892 USA
| | - C Joel McManus
- />Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06030 USA
- />Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213 USA
| | - Dong-Yeon Cho
- />Computational Biology Branch, National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, 8600 Rockville Pike, Bethesda, MD 20892 USA
| | - Matthew Eaton
- />Department of Pharmacology and Cancer Biology, Duke University Medical Center, Levine Science Research Center, 308 Research Drive, Durham, NC 27708 USA
| | - Fioranna Renda
- />Istituto di Biologia e Patologia Molecolari (IBPM) del CNR and Dipartimento di Biologia e Biotecnologie, Sapienza, Università di Roma, 5 Aldo Moro Piazzale, Rome, 00185 Italy
| | - Maria Patrizia Somma
- />Istituto di Biologia e Patologia Molecolari (IBPM) del CNR and Dipartimento di Biologia e Biotecnologie, Sapienza, Università di Roma, 5 Aldo Moro Piazzale, Rome, 00185 Italy
| | - Lucy Cherbas
- />Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405 USA
| | - Gemma May
- />Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06030 USA
- />Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213 USA
| | - Sara Powell
- />Department of Pharmacology and Cancer Biology, Duke University Medical Center, Levine Science Research Center, 308 Research Drive, Durham, NC 27708 USA
| | - Dayu Zhang
- />Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405 USA
- />School of Agricultural and Food Science, Zhejiang A&F University, 88 Huan Cheng Bei Road, Lin’an, Zhejiang 311300 China
| | - Lijun Zhan
- />Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06030 USA
| | - Alissa Resch
- />Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06030 USA
| | - Justen Andrews
- />Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405 USA
| | - Susan E Celniker
- />Department of Genome Dynamics, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 USA
| | - Peter Cherbas
- />Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405 USA
| | - Teresa M Przytycka
- />Computational Biology Branch, National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, 8600 Rockville Pike, Bethesda, MD 20892 USA
| | - Maurizio Gatti
- />Istituto di Biologia e Patologia Molecolari (IBPM) del CNR and Dipartimento di Biologia e Biotecnologie, Sapienza, Università di Roma, 5 Aldo Moro Piazzale, Rome, 00185 Italy
| | - Brian Oliver
- />National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, 50 South Drive, Bethesda, MD 20892 USA
| | - Brenton Graveley
- />Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06030 USA
| | - David MacAlpine
- />Department of Pharmacology and Cancer Biology, Duke University Medical Center, Levine Science Research Center, 308 Research Drive, Durham, NC 27708 USA
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Basquin D, Spierer A, Begeot F, Koryakov DE, Todeschini AL, Ronsseray S, Vieira C, Spierer P, Delattre M. The Drosophila Su(var)3-7 gene is required for oogenesis and female fertility, genetically interacts with piwi and aubergine, but impacts only weakly transposon silencing. PLoS One 2014; 9:e96802. [PMID: 24820312 PMCID: PMC4018442 DOI: 10.1371/journal.pone.0096802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 04/11/2014] [Indexed: 11/19/2022] Open
Abstract
Heterochromatin is made of repetitive sequences, mainly transposable elements (TEs), the regulation of which is critical for genome stability. We have analyzed the role of the heterochromatin-associated Su(var)3-7 protein in Drosophila ovaries. We present evidences that Su(var)3-7 is required for correct oogenesis and female fertility. It accumulates in heterochromatic domains of ovarian germline and somatic cells nuclei, where it co-localizes with HP1. Homozygous mutant females display ovaries with frequent degenerating egg-chambers. Absence of Su(var)3-7 in embryos leads to defects in meiosis and first mitotic divisions due to chromatin fragmentation or chromosome loss, showing that Su(var)3-7 is required for genome integrity. Females homozygous for Su(var)3-7 mutations strongly impair repression of P-transposable element induced gonadal dysgenesis but have minor effects on other TEs. Su(var)3-7 mutations reduce piRNA cluster transcription and slightly impact ovarian piRNA production. However, this modest piRNA reduction does not correlate with transposon de-silencing, suggesting that the moderate effect of Su(var)3-7 on some TE repression is not linked to piRNA production. Strikingly, Su(var)3-7 genetically interacts with the piwi and aubergine genes, key components of the piRNA pathway, by strongly impacting female fertility without impairing transposon silencing. These results lead us to propose that the interaction between Su(var)3-7 and piwi or aubergine controls important developmental processes independently of transposon silencing.
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Affiliation(s)
- Denis Basquin
- Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland
| | - Anne Spierer
- Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland
| | - Flora Begeot
- Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland
| | | | - Anne-Laure Todeschini
- Laboratoire Biologie du Développement, UMR7622, CNRS-Université Pierre et Marie Curie, Paris, France
| | - Stéphane Ronsseray
- Laboratoire Biologie du Développement, UMR7622, CNRS-Université Pierre et Marie Curie, Paris, France
| | - Cristina Vieira
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université Lyon1, Villeurbanne, France
- Institut Universitaire de France, Paris, France
| | - Pierre Spierer
- Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland
| | - Marion Delattre
- Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland
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Milán M, Clemente-Ruiz M, Dekanty A, Muzzopappa M. Aneuploidy and tumorigenesis in Drosophila. Semin Cell Dev Biol 2014; 28:110-5. [DOI: 10.1016/j.semcdb.2014.03.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/03/2014] [Accepted: 03/10/2014] [Indexed: 12/15/2022]
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Donnelly N, Storchová Z. Dynamic karyotype, dynamic proteome: buffering the effects of aneuploidy. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:473-81. [DOI: 10.1016/j.bbamcr.2013.11.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 11/21/2013] [Accepted: 11/22/2013] [Indexed: 12/18/2022]
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Targeting of Painting of fourth to roX1 and roX2 proximal sites suggests evolutionary links between dosage compensation and the regulation of the fourth chromosome in Drosophila melanogaster. G3-GENES GENOMES GENETICS 2013; 3:1325-34. [PMID: 23733888 PMCID: PMC3737172 DOI: 10.1534/g3.113.006866] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In Drosophila melanogaster, two chromosome-specific targeting and regulatory systems have been described. The male-specific lethal (MSL) complex supports dosage compensation by stimulating gene expression from the male X-chromosome, and the protein Painting of fourth (POF) specifically targets and stimulates expression from the heterochromatic 4(th) chromosome. The targeting sites of both systems are well characterized, but the principles underlying the targeting mechanisms have remained elusive. Here we present an original observation, namely that POF specifically targets two loci on the X-chromosome, PoX1 and PoX2 (POF-on-X). PoX1 and PoX2 are located close to the roX1 and roX2 genes, which encode noncoding RNAs important for the correct targeting and spreading of the MSL-complex. We also found that the targeting of POF to PoX1 and PoX2 is largely dependent on roX expression and identified a high-affinity target region that ectopically recruits POF. The results presented support a model linking the MSL-complex to POF and dosage compensation to regulation of heterochromatin.
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Elgin SCR, Reuter G. Position-effect variegation, heterochromatin formation, and gene silencing in Drosophila. Cold Spring Harb Perspect Biol 2013; 5:a017780. [PMID: 23906716 DOI: 10.1101/cshperspect.a017780] [Citation(s) in RCA: 321] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Position-effect variegation (PEV) results when a gene normally in euchromatin is juxtaposed with heterochromatin by rearrangement or transposition. When heterochromatin packaging spreads across the heterochromatin/euchromatin border, it causes transcriptional silencing in a stochastic pattern. PEV is intensely studied in Drosophila using the white gene. Screens for dominant mutations that suppress or enhance white variegation have identified many conserved epigenetic factors, including the histone H3 lysine 9 methyltransferase SU(VAR)3-9. Heterochromatin protein HP1a binds H3K9me2/3 and interacts with SU(VAR)3-9, creating a core memory system. Genetic, molecular, and biochemical analysis of PEV in Drosophila has contributed many key findings concerning establishment and maintenance of heterochromatin with concomitant gene silencing.
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Affiliation(s)
- Sarah C R Elgin
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
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31
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Lundberg LE, Stenberg P, Larsson J. HP1a, Su(var)3-9, SETDB1 and POF stimulate or repress gene expression depending on genomic position, gene length and expression pattern in Drosophila melanogaster. Nucleic Acids Res 2013; 41:4481-94. [PMID: 23476027 PMCID: PMC3632140 DOI: 10.1093/nar/gkt158] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Heterochromatin protein 1a (HP1a) is a chromatin-associated protein important for the formation and maintenance of heterochromatin. In Drosophila, the two histone methyltransferases SETDB1 and Su(var)3-9 mediate H3K9 methylation marks that initiates the establishment and spreading of HP1a-enriched chromatin. Although HP1a is generally regarded as a factor that represses gene transcription, several reports have linked HP1a binding to active genes, and in some cases, it has been shown to stimulate transcriptional activity. To clarify the function of HP1a in transcription regulation and its association with Su(var)3-9, SETDB1 and the chromosome 4-specific protein POF, we conducted genome-wide expression studies and combined the results with available binding data in Drosophila melanogaster. The results suggest that HP1a, SETDB1 and Su(var)3-9 repress genes on chromosome 4, where non-ubiquitously expressed genes are preferentially targeted, and stimulate genes in pericentromeric regions. Further, we showed that on chromosome 4, Su(var)3-9, SETDB1 and HP1a target the same genes. In addition, we found that transposons are repressed by HP1a and Su(var)3-9 and that the binding level and expression effects of HP1a are affected by gene length. Our results indicate that genes have adapted to be properly expressed in their local chromatin environment.
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Affiliation(s)
- Lina E Lundberg
- Department of Molecular Biology, Umeå University, SE-90187 Umeå, Sweden
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32
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Li J, Hobman TC, Simmonds AJ. Gawky (GW) is the Drosophila melanogaster GW182 homologue. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 768:127-45. [PMID: 23224968 DOI: 10.1007/978-1-4614-5107-5_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Jing Li
- Department of Cell Biology, University of Alberta, Edmonton, Canada.
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33
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Figueiredo MLA, Philip P, Stenberg P, Larsson J. HP1a recruitment to promoters is independent of H3K9 methylation in Drosophila melanogaster. PLoS Genet 2012; 8:e1003061. [PMID: 23166515 PMCID: PMC3499360 DOI: 10.1371/journal.pgen.1003061] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 09/19/2012] [Indexed: 11/19/2022] Open
Abstract
Heterochromatin protein 1 (HP1) proteins, recognized readers of the heterochromatin mark methylation of histone H3 lysine 9 (H3K9me), are important regulators of heterochromatin-mediated gene silencing and chromosome structure. In Drosophila melanogaster three histone lysine methyl transferases (HKMTs) are associated with the methylation of H3K9: Su(var)3-9, Setdb1, and G9a. To probe the dependence of HP1a binding on H3K9me, its dependence on these three HKMTs, and the division of labor between the HKMTs, we have examined correlations between HP1a binding and H3K9me patterns in wild type and null mutants of these HKMTs. We show here that Su(var)3-9 controls H3K9me-dependent binding of HP1a in pericentromeric regions, while Setdb1 controls it in cytological region 2L:31 and (together with POF) in chromosome 4. HP1a binds to the promoters and within bodies of active genes in these three regions. More importantly, however, HP1a binding at promoters of active genes is independent of H3K9me and POF. Rather, it is associated with heterochromatin protein 2 (HP2) and open chromatin. Our results support a hypothesis in which HP1a nucleates with high affinity independently of H3K9me in promoters of active genes and then spreads via H3K9 methylation and transient looping contacts with those H3K9me target sites. HP1 is a key protein in heterochromatin and epigenetic silencing, a phenomenon involving chromatin condensation. It is generally accepted that HP1 forms a dimer that links two adjacent nucleosomes through interactions with histone 3 methylated at lysine 9 (H3K9me). Since HP1 also interacts with the histone lysine methyltransferases (HKMTs) generating this modification, histone H3 becomes methylated and HP1 spreading is propagated. Here, we show that HP1a in Drosophila binds to promoters of active genes on chromosome 4 and pericentromeric regions. In contrast to current dogma, this binding is independent of H3K9me. In the presence of the HKMTs and H3K9me, HP1a is also enriched within the bodies of the bound genes. These findings shed new light on the role of HP1a and the epigenetic nature of this chromatin mark. We propose that HP1a interacts independently of H3K9me with the nucleosome with high affinity, probably via the H3 histone-fold. This interaction is followed by a more transient interaction between HP1a and H3K9me, which results in spreading of the HP1a enrichment into gene bodies. Overall, the presented results and hypothesized model provide an explanation for this epigenetic mark and possibly more general insights into the relationships between chromo-domain proteins and methylated histones.
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Affiliation(s)
| | - Philge Philip
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Computational Life Science Cluster (CLiC), Umeå University, Umeå, Sweden
| | - Per Stenberg
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Computational Life Science Cluster (CLiC), Umeå University, Umeå, Sweden
| | - Jan Larsson
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- * E-mail:
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34
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Meisel RP, Malone JH, Clark AG. Faster-X evolution of gene expression in Drosophila. PLoS Genet 2012; 8:e1003013. [PMID: 23071459 PMCID: PMC3469423 DOI: 10.1371/journal.pgen.1003013] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 08/22/2012] [Indexed: 01/01/2023] Open
Abstract
DNA sequences on X chromosomes often have a faster rate of evolution when compared to similar loci on the autosomes, and well articulated models provide reasons why the X-linked mode of inheritance may be responsible for the faster evolution of X-linked genes. We analyzed microarray and RNA-seq data collected from females and males of six Drosophila species and found that the expression levels of X-linked genes also diverge faster than autosomal gene expression, similar to the "faster-X" effect often observed in DNA sequence evolution. Faster-X evolution of gene expression was recently described in mammals, but it was limited to the evolutionary lineages shortly following the creation of the therian X chromosome. In contrast, we detect a faster-X effect along both deep lineages and those on the tips of the Drosophila phylogeny. In Drosophila males, the dosage compensation complex (DCC) binds the X chromosome, creating a unique chromatin environment that promotes the hyper-expression of X-linked genes. We find that DCC binding, chromatin environment, and breadth of expression are all predictive of the rate of gene expression evolution. In addition, estimates of the intraspecific genetic polymorphism underlying gene expression variation suggest that X-linked expression levels are not under relaxed selective constraints. We therefore hypothesize that the faster-X evolution of gene expression is the result of the adaptive fixation of beneficial mutations at X-linked loci that change expression level in cis. This adaptive faster-X evolution of gene expression is limited to genes that are narrowly expressed in a single tissue, suggesting that relaxed pleiotropic constraints permit a faster response to selection. Finally, we present a conceptional framework to explain faster-X expression evolution, and we use this framework to examine differences in the faster-X effect between Drosophila and mammals.
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Affiliation(s)
- Richard P Meisel
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA.
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35
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Enrichment of HP1a on Drosophila chromosome 4 genes creates an alternate chromatin structure critical for regulation in this heterochromatic domain. PLoS Genet 2012; 8:e1002954. [PMID: 23028361 PMCID: PMC3447959 DOI: 10.1371/journal.pgen.1002954] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 07/31/2012] [Indexed: 02/06/2023] Open
Abstract
Chromatin environments differ greatly within a eukaryotic genome, depending on expression state, chromosomal location, and nuclear position. In genomic regions characterized by high repeat content and high gene density, chromatin structure must silence transposable elements but permit expression of embedded genes. We have investigated one such region, chromosome 4 of Drosophila melanogaster. Using chromatin-immunoprecipitation followed by microarray (ChIP-chip) analysis, we examined enrichment patterns of 20 histone modifications and 25 chromosomal proteins in S2 and BG3 cells, as well as the changes in several marks resulting from mutations in key proteins. Active genes on chromosome 4 are distinct from those in euchromatin or pericentric heterochromatin: while there is a depletion of silencing marks at the transcription start sites (TSSs), HP1a and H3K9me3, but not H3K9me2, are enriched strongly over gene bodies. Intriguingly, genes on chromosome 4 are less frequently associated with paused polymerase. However, when the chromatin is altered by depleting HP1a or POF, the RNA pol II enrichment patterns of many chromosome 4 genes shift, showing a significant decrease over gene bodies but not at TSSs, accompanied by lower expression of those genes. Chromosome 4 genes have a low incidence of TRL/GAGA factor binding sites and a low T(m) downstream of the TSS, characteristics that could contribute to a low incidence of RNA polymerase pausing. Our data also indicate that EGG and POF jointly regulate H3K9 methylation and promote HP1a binding over gene bodies, while HP1a targeting and H3K9 methylation are maintained at the repeats by an independent mechanism. The HP1a-enriched, POF-associated chromatin structure over the gene bodies may represent one type of adaptation for genes embedded in repetitive DNA.
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36
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POF regulates the expression of genes on the fourth chromosome in Drosophila melanogaster by binding to nascent RNA. Mol Cell Biol 2012; 32:2121-34. [PMID: 22473994 DOI: 10.1128/mcb.06622-11] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In Drosophila, two chromosome-wide compensatory systems have been characterized: the dosage compensation system that acts on the male X chromosome and the chromosome-specific regulation of genes located on the heterochromatic fourth chromosome. Dosage compensation in Drosophila is accomplished by hypertranscription of the single male X chromosome mediated by the male-specific lethal (MSL) complex. The mechanism of this compensation is suggested to involve enhanced transcriptional elongation mediated by the MSL complex, while the mechanism of compensation mediated by the painting of fourth (POF) protein on the fourth chromosome has remained elusive. Here, we show that POF binds to nascent RNA, and this binding is associated with increased transcription output from chromosome 4. We also show that genes located in heterochromatic regions spend less time in transition from the site of transcription to the nuclear envelope. These results provide useful insights into the means by which genes in heterochromatic regions can overcome the repressive influence of their hostile environment.
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37
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Lundberg LE, Figueiredo MLA, Stenberg P, Larsson J. Buffering and proteolysis are induced by segmental monosomy in Drosophila melanogaster. Nucleic Acids Res 2012; 40:5926-37. [PMID: 22434883 PMCID: PMC3401434 DOI: 10.1093/nar/gks245] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Variation in the number of individual chromosomes (chromosomal aneuploidy) or chromosome segments (segmental aneuploidy) is associated with developmental abnormalities and reduced fitness in all species examined; it is the leading cause of miscarriages and mental retardation and a hallmark of cancer. However, despite their documented importance in disease, the effects of aneuploidies on the transcriptome remain largely unknown. We have examined the expression effects of seven heterozygous chromosomal deficiencies, both singly and in all pairwise combinations, in Drosophila melanogaster. The results show that genes in one copy are buffered, i.e. expressed more strongly than the expected 50% of wild-type level, the buffering is general and not influenced by other monosomic regions. Furthermore, long genes are significantly more highly buffered than short genes and gene length appears to be the primary determinant of the buffering degree. For short genes the degree of buffering depends on expression level and expression pattern. Furthermore, the results show that in deficiency heterozygotes the expression of genes involved in proteolysis is enhanced and negatively correlates with the degree of buffering. Thus, enhanced proteolysis appears to be a general response to aneuploidy.
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Affiliation(s)
- Lina E Lundberg
- Department of Molecular Biology, Umeå University, SE-90187 Umeå, Sweden
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38
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Stenberg P, Larsson J. Buffering and the evolution of chromosome-wide gene regulation. Chromosoma 2011; 120:213-25. [PMID: 21505791 PMCID: PMC3098985 DOI: 10.1007/s00412-011-0319-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 03/15/2011] [Accepted: 03/31/2011] [Indexed: 11/30/2022]
Abstract
Copy number variation (CNV) in terms of aneuploidies of both entire chromosomes and chromosomal segments is an important evolutionary driving force, but it is inevitably accompanied by potentially problematic variations in gene doses and genomic instability. Thus, a delicate balance must be maintained between mechanisms that compensate for variations in gene doses (and thus allow such genomic variability) and selection against destabilizing CNVs. In Drosophila, three known compensatory mechanisms have evolved: a general segmental aneuploidy-buffering system and two chromosome-specific systems. The two chromosome-specific systems are the male-specific lethal complex, which is important for dosage compensation of the male X chromosome, and Painting of fourth, which stimulates expression of the fourth chromosome. In this review, we discuss the origin and function of buffering and compensation using Drosophila as a model.
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Affiliation(s)
- Per Stenberg
- Department of Molecular Biology, Umeå University, Sweden
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39
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Kwon SH, Workman JL. The changing faces of HP1: From heterochromatin formation and gene silencing to euchromatic gene expression: HP1 acts as a positive regulator of transcription. Bioessays 2011; 33:280-9. [PMID: 21271610 DOI: 10.1002/bies.201000138] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Heterochromatin protein 1 (HP1) is a positive regulator of active transcription in euchromatin. HP1 was first identified in Drosophila melanogaster as a major component of heterochromatin. Most eukaryotes have at least three isoforms of HP1, which are conserved in overall structure but localize differentially to heterochromatin and euchromatin. Although initial studies revealed a key role for HP1 in heterochromatin formation and gene silencing, recent progress has shed light on additional roles for HP1 in processes such as euchromatic gene expression. Recent studies have highlighted the importance of HP1-mediated gene regulation in euchromatin. Here, we focus on recent advances in understanding the role of HP1 in active transcription in euchromatin and how modification and localization of HP1 can regulate distinct functions for this protein in different contexts.
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Affiliation(s)
- So Hee Kwon
- Stowers Institute for Medical Research, Kansas City, MO, USA
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40
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Riddle NC, Minoda A, Kharchenko PV, Alekseyenko AA, Schwartz YB, Tolstorukov MY, Gorchakov AA, Jaffe JD, Kennedy C, Linder-Basso D, Peach SE, Shanower G, Zheng H, Kuroda MI, Pirrotta V, Park PJ, Elgin SC, Karpen GH. Plasticity in patterns of histone modifications and chromosomal proteins in Drosophila heterochromatin. Genome Res 2011; 21:147-63. [PMID: 21177972 PMCID: PMC3032919 DOI: 10.1101/gr.110098.110] [Citation(s) in RCA: 214] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2010] [Accepted: 12/08/2010] [Indexed: 12/18/2022]
Abstract
Eukaryotic genomes are packaged in two basic forms, euchromatin and heterochromatin. We have examined the composition and organization of Drosophila melanogaster heterochromatin in different cell types using ChIP-array analysis of histone modifications and chromosomal proteins. As anticipated, the pericentric heterochromatin and chromosome 4 are on average enriched for the "silencing" marks H3K9me2, H3K9me3, HP1a, and SU(VAR)3-9, and are generally depleted for marks associated with active transcription. The locations of the euchromatin-heterochromatin borders identified by these marks are similar in animal tissues and most cell lines, although the amount of heterochromatin is variable in some cell lines. Combinatorial analysis of chromatin patterns reveals distinct profiles for euchromatin, pericentric heterochromatin, and the 4th chromosome. Both silent and active protein-coding genes in heterochromatin display complex patterns of chromosomal proteins and histone modifications; a majority of the active genes exhibit both "activation" marks (e.g., H3K4me3 and H3K36me3) and "silencing" marks (e.g., H3K9me2 and HP1a). The hallmark of active genes in heterochromatic domains appears to be a loss of H3K9 methylation at the transcription start site. We also observe complex epigenomic profiles of intergenic regions, repeated transposable element (TE) sequences, and genes in the heterochromatic extensions. An unexpectedly large fraction of sequences in the euchromatic chromosome arms exhibits a heterochromatic chromatin signature, which differs in size, position, and impact on gene expression among cell types. We conclude that patterns of heterochromatin/euchromatin packaging show greater complexity and plasticity than anticipated. This comprehensive analysis provides a foundation for future studies of gene activity and chromosomal functions that are influenced by or dependent upon heterochromatin.
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Affiliation(s)
- Nicole C. Riddle
- Department of Biology, Washington University St. Louis, Missouri 63130, USA
| | - Aki Minoda
- Department of Molecular and Cell Biology, University of California at Berkeley and Department of Genome Dynamics, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Peter V. Kharchenko
- Center for Biomedical Informatics, Harvard Medical School and Informatics Program, Children's Hospital, Boston, Massachusetts 02115, USA
| | - Artyom A. Alekseyenko
- Division of Genetics, Department of Medicine, Brigham & Women's Hospital, and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Yuri B. Schwartz
- Department of Molecular Biology & Biochemistry, Rutgers University, Piscataway, New Jersey 08901, USA
- Department of Molecular Biology, Umea University, 90187 Umea, Sweden
| | - Michael Y. Tolstorukov
- Center for Biomedical Informatics, Harvard Medical School and Informatics Program, Children's Hospital, Boston, Massachusetts 02115, USA
| | - Andrey A. Gorchakov
- Division of Genetics, Department of Medicine, Brigham & Women's Hospital, and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Jacob D. Jaffe
- Proteomics Group, The Broad Institute, Cambridge, Massachusetts 02139, USA
| | - Cameron Kennedy
- Department of Molecular and Cell Biology, University of California at Berkeley and Department of Genome Dynamics, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Daniela Linder-Basso
- Department of Molecular Biology & Biochemistry, Rutgers University, Piscataway, New Jersey 08901, USA
| | - Sally E. Peach
- Proteomics Group, The Broad Institute, Cambridge, Massachusetts 02139, USA
| | - Gregory Shanower
- Department of Molecular Biology & Biochemistry, Rutgers University, Piscataway, New Jersey 08901, USA
| | - Haiyan Zheng
- Biological Mass Spectrometry Resource, Center for Advanced Biotechnology and Medicine, University of Dentistry and Medicine of New Jersey, Piscataway, New Jersey 08854, USA
| | - Mitzi I. Kuroda
- Division of Genetics, Department of Medicine, Brigham & Women's Hospital, and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Vincenzo Pirrotta
- Department of Molecular Biology & Biochemistry, Rutgers University, Piscataway, New Jersey 08901, USA
| | - Peter J. Park
- Center for Biomedical Informatics, Harvard Medical School and Informatics Program, Children's Hospital, Boston, Massachusetts 02115, USA
| | - Sarah C.R. Elgin
- Department of Biology, Washington University St. Louis, Missouri 63130, USA
| | - Gary H. Karpen
- Department of Molecular and Cell Biology, University of California at Berkeley and Department of Genome Dynamics, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
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41
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Dyer KA, White BE, Bray MJ, Piqué DG, Betancourt AJ. Molecular evolution of a Y chromosome to autosome gene duplication in Drosophila. Mol Biol Evol 2010; 28:1293-306. [PMID: 21172827 DOI: 10.1093/molbev/msq334] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In contrast to the rest of the genome, the Y chromosome is restricted to males and lacks recombination. As a result, Y chromosomes are unable to respond efficiently to selection, and newly formed Y chromosomes degenerate until few genes remain. The rapid loss of genes from newly formed Y chromosomes has been well studied, but gene loss from highly degenerate Y chromosomes has only recently received attention. Here, we identify and characterize a Y to autosome duplication of the male fertility gene kl-5 that occurred during the evolution of the testacea group species of Drosophila. The duplication was likely DNA based, as other Y-linked genes remain on the Y chromosome, the locations of introns are conserved, and expression analyses suggest that regulatory elements remain linked. Genetic mapping reveals that the autosomal copy of kl-5 resides on the dot chromosome, a tiny autosome with strongly suppressed recombination. Molecular evolutionary analyses show that autosomal copies of kl-5 have reduced polymorphism and little recombination. Importantly, the rate of protein evolution of kl-5 has increased significantly in lineages where it is on the dot versus Y linked. Further analyses suggest this pattern is a consequence of relaxed purifying selection, rather than adaptive evolution. Thus, although the initial fixation of the kl-5 duplication may have been advantageous, slightly deleterious mutations have accumulated in the dot-linked copies of kl-5 faster than in the Y-linked copies. Because the dot chromosome contains seven times more genes than the Y and is exposed to selection in both males and females, these results suggest that the dot suffers the deleterious effects of genetic linkage to more selective targets compared with the Y chromosome. Thus, a highly degenerate Y chromosome may not be the worst environment in the genome, as is generally thought, but may in fact be protected from the accumulation of deleterious mutations relative to other nonrecombining regions that contain more genes.
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Affiliation(s)
- Kelly A Dyer
- Department of Genetics, University of Georgia, GA, USA.
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42
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Yan H, Venkatesan K, Beaver JE, Klitgord N, Yildirim MA, Hao T, Hill DE, Cusick ME, Perrimon N, Roth FP, Vidal M. A genome-wide gene function prediction resource for Drosophila melanogaster. PLoS One 2010; 5:e12139. [PMID: 20711346 PMCID: PMC2920829 DOI: 10.1371/journal.pone.0012139] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 07/14/2010] [Indexed: 11/19/2022] Open
Abstract
Predicting gene functions by integrating large-scale biological data remains a challenge for systems biology. Here we present a resource for Drosophila melanogaster gene function predictions. We trained function-specific classifiers to optimize the influence of different biological datasets for each functional category. Our model predicted GO terms and KEGG pathway memberships for Drosophila melanogaster genes with high accuracy, as affirmed by cross-validation, supporting literature evidence, and large-scale RNAi screens. The resulting resource of prioritized associations between Drosophila genes and their potential functions offers a guide for experimental investigations.
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Affiliation(s)
- Han Yan
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Kavitha Venkatesan
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - John E. Beaver
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Niels Klitgord
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Muhammed A. Yildirim
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Applied Physics Program, Division of Engineering and Applied Sciences, Graduate School of Arts and Sciences, Harvard University, Cambridge, Massachusetts, United States of America
| | - Tong Hao
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - David E. Hill
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael E. Cusick
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Norbert Perrimon
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Frederick P. Roth
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (FPR); (MV)
| | - Marc Vidal
- Department of Cancer Biology, Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (FPR); (MV)
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43
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Larracuente AM, Noor MAF, Clark AG. Translocation of Y-linked genes to the dot chromosome in Drosophila pseudoobscura. Mol Biol Evol 2010; 27:1612-20. [PMID: 20147437 DOI: 10.1093/molbev/msq045] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
One of the most striking cases of sex chromosome reorganization in Drosophila occurred in the lineage ancestral to Drosophila pseudoobscura, where there was a translocation of Y-linked genes to an autosome. These genes went from being present only in males, never recombining, and having an effective population size of 0.5N to a state of autosomal linkage, where they are passed through both sexes, may recombine, and their effective population size has quadrupled. These genes appear to be functional, and they underwent a drastic reduction in intron size after the translocation. A Y-autosome translocation may pose problems in meiosis if the rDNA locus responsible for X-Y pairing had also moved to an autosome. In this study, we demonstrate that the Y-autosome translocation moved Y-linked genes onto the dot chromosome, a small, mainly heterochromatic autosome with some sex chromosome-like properties. The rDNA repeats occur exclusively on the X chromosome in D. pseudoobscura, but we found that the new Y chromosome of this species harbors four clusters bearing only the intergenic spacer region (IGS) of the rDNA repeats. This arrangement appears analogous to the situation in Drosophila simulans, where X-rDNA to Y-IGS pairing could be responsible for X-Y chromosome pairing. We postulate that the nascent D. pseudoobscura Y chromosome acquired and amplified copies of the IGS, suggesting a potential mechanism for X-Y pairing in D. pseudoobscura.
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Affiliation(s)
- Amanda M Larracuente
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA.
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Koch CM, Honemann-Capito M, Egger-Adam D, Wodarz A. Windei, the Drosophila homolog of mAM/MCAF1, is an essential cofactor of the H3K9 methyl transferase dSETDB1/Eggless in germ line development. PLoS Genet 2009; 5:e1000644. [PMID: 19750210 PMCID: PMC2730569 DOI: 10.1371/journal.pgen.1000644] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Accepted: 08/13/2009] [Indexed: 01/26/2023] Open
Abstract
The epigenetic regulation of gene expression by the covalent modification of histones is a fundamental mechanism required for the proper differentiation of germ line cells during development. Trimethylation of histone 3 lysine 9 (H3K9me3) leads to chromatin silencing and the formation of heterochromatin by recruitment of heterochromatin protein 1 (HP1). dSETDB1/Eggless (Egg), the ortholog of the human methyltransferase SETDB1, is the only essential H3K9 methyltransferase in Drosophila and is required for H3K9 trimethylation in the female germ line. Here we show that Windei (Wde), the Drosophila homolog of mouse mAM and human MCAF1, is an essential cofactor of Egg required for its nuclear localization and function in female germ line cells. By deletion analysis combined with coimmunoprecipitation, we have identified the protein regions in Wde and Egg that are necessary and sufficient for the interaction between the two proteins. We furthermore identified a region of Egg that gets covalently modified by SUMOylation, which may facilitate the formation of higher order chromatin-modifying complexes. Together with Egg, Wde localizes to euchromatin, is enriched on chromosome 4, and binds to the Painting of fourth (POF) protein. Our data provide the first genetic and phenotypic analysis of a mAM/MCAF1 homolog in a model organism and demonstrate its essential function in the survival of germ line cells.
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Affiliation(s)
- Carmen M. Koch
- Abteilung Stammzellbiologie, DFG Research Center for Molecular Physiology of the Brain (CMPB), Georg-August-Universität Göttingen, Göttingen, Germany
| | - Mona Honemann-Capito
- Abteilung Stammzellbiologie, DFG Research Center for Molecular Physiology of the Brain (CMPB), Georg-August-Universität Göttingen, Göttingen, Germany
| | - Diane Egger-Adam
- Abteilung Stammzellbiologie, DFG Research Center for Molecular Physiology of the Brain (CMPB), Georg-August-Universität Göttingen, Göttingen, Germany
- Fakultät für Biologie, Universität Konstanz, Konstanz, Germany
| | - Andreas Wodarz
- Abteilung Stammzellbiologie, DFG Research Center for Molecular Physiology of the Brain (CMPB), Georg-August-Universität Göttingen, Göttingen, Germany
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Removal of the bloom syndrome DNA helicase extends the utility of imprecise transposon excision for making null mutations in Drosophila. Genetics 2009; 183:1187-93. [PMID: 19687136 DOI: 10.1534/genetics.109.108472] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transposable elements are frequently used in Drosophila melanogaster for imprecise excision screens to delete genes of interest. However, these screens are highly variable in the number and size of deletions that are recovered. Here, we show that conducting excision screens in mus309 mutant flies that lack DmBlm, the Drosophila ortholog of the Bloom syndrome protein, increases the percentage and overall size of flanking deletions recovered after excision of either P or Minos elements.
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Riddle NC, Shaffer CD, Elgin SCR. A lot about a little dot - lessons learned from Drosophila melanogaster chromosome 4. Biochem Cell Biol 2009; 87:229-41. [PMID: 19234537 DOI: 10.1139/o08-119] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The fourth chromosome of Drosophila melanogaster has a number of unique properties that make it a convenient model for the study of chromatin structure. Only 4.2 Mb overall, the 1.2 Mb distal arm of chromosome 4 seen in polytene chromosomes combines characteristics of heterochromatin and euchromatin. This domain has a repeat density of ~35%, comparable to some pericentric chromosome regions, while maintaining a gene density similar to that of the other euchromatic chromosome arms. Studies of position-effect variegation have revealed that heterochromatic and euchromatic domains are interspersed on chromosome 4, and both cytological and biochemical studies have demonstrated that chromosome 4 is associated with heterochromatic marks, such as heterochromatin protein 1 and histone 3 lysine 9 methylation. Chromosome 4 is also marked by POF (painting-of-fourth), a chromosome 4-specific chromosomal protein, and utilizes a dedicated histone methyltransferase, EGG. Studies of chromosome 4 have helped to shape our understanding of heterochromatin domains and their establishment and maintenance. In this review, we provide a synthesis of the work to date and an outlook to the future.
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Affiliation(s)
- Nicole C Riddle
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
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Stenberg P, Lundberg LE, Johansson AM, Rydén P, Svensson MJ, Larsson J. Buffering of segmental and chromosomal aneuploidies in Drosophila melanogaster. PLoS Genet 2009; 5:e1000465. [PMID: 19412336 PMCID: PMC2668767 DOI: 10.1371/journal.pgen.1000465] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Accepted: 03/30/2009] [Indexed: 01/17/2023] Open
Abstract
Chromosomal instability, which involves the deletion and duplication of chromosomes or chromosome parts, is a common feature of cancers, and deficiency screens are commonly used to detect genes involved in various biological pathways. However, despite their importance, the effects of deficiencies, duplications, and chromosome losses on the regulation of whole chromosomes and large chromosome domains are largely unknown. Therefore, to explore these effects, we examined expression patterns of genes in several Drosophila deficiency hemizygotes and a duplication hemizygote using microarrays. The results indicate that genes expressed in deficiency hemizygotes are significantly buffered, and that the buffering effect is general rather than being mainly mediated by feedback regulation of individual genes. In addition, differentially expressed genes in haploid condition appear to be generally more strongly buffered than ubiquitously expressed genes in haploid condition, but, among genes present in triploid condition, ubiquitously expressed genes are generally more strongly buffered than differentially expressed genes. Furthermore, we show that the 4th chromosome is compensated in response to dose differences. Our results suggest general mechanisms have evolved that stimulate or repress gene expression of aneuploid regions as appropriate, and on the 4th chromosome of Drosophila this compensation is mediated by Painting of Fourth (POF). Although deletion heterozygotes and chromosomal aneuploidies have been used in genetic studies for decades, the relationships between chromosome doses and transcript outputs have been difficult to unravel. In other words, the effects of copy changes on the regulation of entire chromosomes or large chromosomal domains are largely unknown. Hence, we studied these relationships in Drosophila using microarrays prepared from flies with a dosage series of chromosomal domains and a dosage series of the 4th chromosome. We observed significant buffering of expressed genes, i.e., on average they were expressed at >50% of wild-type levels when present in single copies instead of two copies (the normal complement of diploids). This buffering was also seen to be much stronger for differentially expressed genes than ubiquitously expressed genes. Our findings therefore support the presence of chromosome-wide buffering mechanisms. In addition, we found evidence of a chromosome-specific protein POF-mediated mechanism in the buffering of the 4th chromosome. Overall, our results suggest that a general buffering system acts on most genes present as single copies due to deletions or chromosome losses. Further work on gene buffering effects should make substantial contributions to our understanding of genome-wide gene regulation.
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Affiliation(s)
- Per Stenberg
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Computational Life Science Cluster (CLiC), Umeå University, Umeå, Sweden
| | | | | | - Patrik Rydén
- Computational Life Science Cluster (CLiC), Umeå University, Umeå, Sweden
- Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden
- Department of Statistics, Umeå University, Umeå, Sweden
| | | | - Jan Larsson
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- * E-mail:
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Blauwkamp TA, Csankovszki G. Two classes of dosage compensation complex binding elements along Caenorhabditis elegans X chromosomes. Mol Cell Biol 2009; 29:2023-31. [PMID: 19188444 PMCID: PMC2663307 DOI: 10.1128/mcb.01448-08] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Revised: 10/21/2008] [Accepted: 01/23/2009] [Indexed: 11/20/2022] Open
Abstract
Dosage compensation equalizes X-linked gene products between the sexes. In Caenorhabditis elegans, the dosage compensation complex (DCC) binds both X chromosomes in XX animals and halves the transcription from each. The DCC is recruited to the X chromosomes by a number of loci, rex sites, and is thought to spread from these sites by an unknown mechanism to cover the rest of the chromosome. Here we describe a novel class of DCC-binding elements that we propose serve as "way stations" for DCC binding and spreading. Both rex sites and way stations comprise strong foci of DCC binding on the native X chromosome. However, rex sites maintain their ability to bind large amounts of DCC even on X duplications detached from the native X, while way stations do not. These results suggest that two distinct classes of DCC-binding elements facilitate recruitment and spreading of the DCC along the X chromosome.
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Affiliation(s)
- Timothy A Blauwkamp
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, USA
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Abstract
Dosage compensation modifies the chromatin of X-linked genes to assure equivalent expression in sexes with unequal X chromosome dosage. In Drosophila dosage compensation is achieved by increasing expression from the male X chromosome. The ribonucleoprotein dosage compensation complex (DCC) binds hundreds of sites along the X chromosome and modifies chromatin to facilitate transcription. Loss of roX RNA, an essential component of the DCC, reduces expression from X-linked genes. Surprisingly, loss of roX RNA also reduces expression from genes situated in proximal heterochromatin and on the small, heterochromatic fourth chromosome. Mutation of some, but not all, of the genes encoding DCC proteins produces a similar effect. Reduction of roX function suppresses position effect variegation (PEV), revealing functional alteration in heterochromatin. The effects of roX mutations on heterochromatic gene expression and PEV are limited to males. A sex-limited role for the roX RNAs in autosomal gene expression was unexpected. We propose that this reflects a difference in the heterochromatin of males and females, which serves to accommodate the heterochromatic Y chromosome present in the male nucleus. roX transcripts may thus participate in two distinct regulatory systems that have evolved in response to highly differentiated sex chromosomes: compensation of X-linked gene dosage and modulation of heterochromatin.
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Haddrill PR, Waldron FM, Charlesworth B. Elevated levels of expression associated with regions of the Drosophila genome that lack crossing over. Biol Lett 2009; 4:758-61. [PMID: 18782733 DOI: 10.1098/rsbl.2008.0376] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The recombinational environment influences patterns of molecular evolution through the effects of Hill-Robertson interference. Here, we examine genome-wide patterns of gene expression with respect to recombinational environment in Drosophila melanogaster. We find that regions of the genome lacking crossing over exhibit elevated levels of expression, and this is most pronounced for genes on the entirely non-crossing over fourth chromosome. We find no evidence for differences in the patterns of gene expression between regions of high, intermediate and low crossover frequencies. These results suggest that, in the absence of crossing over, selection to maintain control of expression may be compromised, perhaps due to the accumulation of deleterious mutations in regulatory regions. Alternatively, higher gene expression may be evolving to compensate for defective protein products or reduced translational efficiency.
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Affiliation(s)
- Penelope R Haddrill
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, Edinburgh EH9 3JT, UK.
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