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Bauer DuMont VL, White SL, Zinshteyn D, Aquadro CF. Molecular population genetics of Sex-lethal ( Sxl) in the Drosophila melanogaster species group: a locus that genetically interacts with Wolbachia pipientis in Drosophila melanogaster. G3 GENES|GENOMES|GENETICS 2021; 11:6296609. [PMID: 34849818 PMCID: PMC8496275 DOI: 10.1093/g3journal/jkab197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 06/01/2021] [Indexed: 11/13/2022]
Abstract
Abstract
Sex-lethal (Sxl) is the sex determination switch in Drosophila, and also plays a critical role in germ-line stem cell daughter differentiation in Drosophila melanogaster. Three female-sterile alleles at Sxl in D. melanogaster were previously shown to genetically interact to varying degrees with the maternally inherited endosymbiont Wolbachia pipientis. Given this genetic interaction and W. pipientis’ ability to manipulate reproduction in Drosophila, we carried out a careful study of both the population genetics (within four Drosophila species) and molecular evolutionary analysis (across 20 Drosophila species) of Sxl. Consistent with earlier studies, we find that selective constraint has played a prominent role in Sxl’s molecular evolution within Drosophila, but we also observe patterns that suggest both episodic bursts of protein evolution and recent positive selection at Sxl. The episodic nature of Sxl’s protein evolution is discussed in light of its genetic interaction with W. pipientis.
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Affiliation(s)
| | - Simone L White
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Daniel Zinshteyn
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Charles F Aquadro
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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2
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Abstract
Sexual size dimorphism (SSD), a sex difference in body size, is widespread throughout the animal kingdom, raising the question of how sex influences existing growth regulatory pathways to bring about SSD. In insects, somatic sexual differentiation has long been considered to be controlled strictly cell-autonomously. Here, we discuss our surprising finding that in Drosophila larvae, the sex determination gene Sex-lethal (Sxl) functions in neurons to non-autonomously specify SSD. We found that Sxl is required in specific neuronal subsets to upregulate female body growth, including in the neurosecretory insulin producing cells, even though insulin-like peptides themselves appear not to be involved. SSD regulation by neuronal Sxl is also independent of its known splicing targets, transformer and msl-2, suggesting that it involves a new molecular mechanism. Interestingly, SSD control by neuronal Sxl is selective for larval, not imaginal tissue types, and operates in addition to cell-autonomous effects of Sxl and Tra, which are present in both larval and imaginal tissues. Overall, our findings add to a small but growing number of studies reporting non-autonomous, likely hormonal, control of sex differences in Drosophila, and suggest that the principles of sexual differentiation in insects and mammals may be more similar than previously thought.
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Affiliation(s)
- Annick Sawala
- a Physiology & Metabolism Laboratory , The Francis Crick Institute , London , UK
| | - Alex P Gould
- a Physiology & Metabolism Laboratory , The Francis Crick Institute , London , UK
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3
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López-Cuadros I, García-Gasca A, Gomez-Anduro G, Escobedo-Fregoso C, Llera-Herrera RA, Ibarra AM. Isolation of the sex-determining gene Sex-lethal (Sxl) in Penaeus (Litopenaeus) vannamei (Boone, 1931) and characterization of its embryogenic, gametogenic, and tissue-specific expression. Gene 2018; 668:33-47. [PMID: 29758296 DOI: 10.1016/j.gene.2018.05.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 05/03/2018] [Accepted: 05/07/2018] [Indexed: 12/11/2022]
Abstract
The Pacific white shrimp Penaeus vannamei is the most cultured shrimp species around the world. Because females grow larger than males, the culture of 'only females' is of great interest, but knowledge on sex determination and differentiation is required for producing only females. In an effort to obtain information associated with reproduction in P. vannamei, transcriptomic data from female gonads was generated, and partial sequences of a transcript were identified as Sex-lethal (Sxl). Its characterization indicated that, differently from other penaeids in which this gene has been isolated, there are six isoforms of the Sxl transcript in P. vannamei (PvanSxl 1-6). These isoforms result from alternative splicing at three splice sites (SS1, SS2, SS3). The first splice-site is unique to P. vannamei, as it has not been reported for other Arthropod species; the second splice-site (SS2) is common among crustaceans, and the third splice-site (SS3) is also unique to P. vannamei and when spliced-out, it is always together with SS2. All isoforms are expressed during embryogenesis as well as gametogenesis of both genders. The two shorter isoforms, PvanSxl-5 and PvanSxl-6, which result from the splicing of SS2 and SS3, were found mostly expressed in adult testis, but PvanSxl-6 was also expressed in oocytes during gametogenesis. During oogenesis, the second largest isoform, PvanSxl-2, which splices-out only SS1, and PvanSxl-4 that splices-out SS1 and SS2 were highly expressed. These two isoforms were also highly expressed during embryonic development. In situ hybridization allowed pinpointing more specifically the cells where the PvanSxl transcripts were expressed. During embryogenesis, hybridization was observed from the one-cell stage embryo to late gastrula. In the female gonad in previtellogenesis, hybridization occurred in the nucleus of oocytes, whereas in secondary vitellogenesis the transcript also hybridized cytoplasmic granules and cortical crypts. Finally, in situ hybridization corroborated the expression of PvanSxl also in the male gonad during spermatogenesis, mostly occurring in the cytoplasm from spermatogonia and spermatocytes.
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Affiliation(s)
- Itzia López-Cuadros
- Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). Programa de Acuacultura, Av. Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur C.P. 23096, Mexico
| | - Alejandra García-Gasca
- Centro de Investigación en Alimentación y Desarrollo A.C., (CIAD) Unidad Mazatlán, Av. Sábalo-Cerritos S/N. Col. Estero del Yugo, C.P. 82000 Mazatlán, Sinaloa, Mexico
| | - Gracia Gomez-Anduro
- Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). Programa de Acuacultura, Av. Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur C.P. 23096, Mexico
| | - Cristina Escobedo-Fregoso
- Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). Programa de Acuacultura, Av. Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur C.P. 23096, Mexico; CONACYT, Consejo Nacional de Ciencia y Tecnología, Av. Insurgentes Sur 1582, Ciudad de México 03940, Mexico
| | - Raúl A Llera-Herrera
- Centro de Investigación en Alimentación y Desarrollo A.C., (CIAD) Unidad Mazatlán, Av. Sábalo-Cerritos S/N. Col. Estero del Yugo, C.P. 82000 Mazatlán, Sinaloa, Mexico; CONACYT, Consejo Nacional de Ciencia y Tecnología, Av. Insurgentes Sur 1582, Ciudad de México 03940, Mexico
| | - Ana M Ibarra
- Centro de Investigaciones Biológicas del Noroeste, S.C. (CIBNOR). Programa de Acuacultura, Av. Instituto Politécnico Nacional No. 195, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur C.P. 23096, Mexico.
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4
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Pancsa R, Macossay-Castillo M, Kosol S, Tompa P. Computational analysis of translational readthrough proteins in Drosophila and yeast reveals parallels to alternative splicing. Sci Rep 2016; 6:32142. [PMID: 27561673 PMCID: PMC4999894 DOI: 10.1038/srep32142] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 07/21/2016] [Indexed: 01/21/2023] Open
Abstract
In translational readthrough (TR) the ribosome continues extending the nascent protein beyond the first in-frame termination codon. Due to the lack of dedicated analyses of eukaryotic TR cases, the associated functional-evolutionary advantages are still unclear. Here, based on a variety of computational methods, we describe the structural and functional properties of previously proposed D. melanogaster and S. cerevisiae TR proteins and extensions. We found that in D. melanogaster TR affects long proteins in mainly regulatory roles. Their TR-extensions are structurally disordered and rich in binding motifs, which, together with their cell-type- and developmental stage-dependent inclusion, suggest that similarly to alternatively spliced exons they rewire cellular interaction networks in a temporally and spatially controlled manner. In contrast, yeast TR proteins are rather short and fulfil mainly housekeeping functions, like translation. Yeast extensions usually lack disorder and linear motifs, which precludes elucidating their functional relevance with sufficient confidence. Therefore we propose that by being much more restricted and by lacking clear functional hallmarks in yeast as opposed to fruit fly, TR shows remarkable parallels with alternative splicing. Additionally, the lack of conservation of TR extensions among orthologous TR proteins suggests that TR-mediated functions may be generally specific to lower taxonomic levels.
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Affiliation(s)
- Rita Pancsa
- Flanders Institute for Biotechnology (VIB), Structural Biology Research Center, Vrije Universiteit Brussel, 1050 Pleinlaan 2, Brussels, Belgium
| | - Mauricio Macossay-Castillo
- Flanders Institute for Biotechnology (VIB), Structural Biology Research Center, Vrije Universiteit Brussel, 1050 Pleinlaan 2, Brussels, Belgium
| | - Simone Kosol
- Flanders Institute for Biotechnology (VIB), Structural Biology Research Center, Vrije Universiteit Brussel, 1050 Pleinlaan 2, Brussels, Belgium
| | - Peter Tompa
- Flanders Institute for Biotechnology (VIB), Structural Biology Research Center, Vrije Universiteit Brussel, 1050 Pleinlaan 2, Brussels, Belgium.,Institute of Enzymology, Research Centre for Natural Sciences of the Hungarian Academy of Sciences, 1117 Budapest, Hungary
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5
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Abstract
Translational readthrough (TR) has come into renewed focus because systems biology approaches have identified the first human genes undergoing functional translational readthrough (FTR). FTR creates functional extensions to proteins by continuing translation of the mRNA downstream of the stop codon. Here we review recent developments in TR research with a focus on the identification of FTR in humans and the systems biology methods that have spurred these discoveries.
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Affiliation(s)
- Fabian Schueren
- University Medical Center, Department of Child and Adolescent Health, University of Göttingen, Göttingen, Germany
| | - Sven Thoms
- University Medical Center, Department of Child and Adolescent Health, University of Göttingen, Göttingen, Germany
- * E-mail:
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Katz MJ, Gándara L, De Lella Ezcurra AL, Wappner P. Hydroxylation and translational adaptation to stress: some answers lie beyond the STOP codon. Cell Mol Life Sci 2016; 73:1881-93. [PMID: 26874685 PMCID: PMC11108485 DOI: 10.1007/s00018-016-2160-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 02/03/2016] [Accepted: 02/04/2016] [Indexed: 01/08/2023]
Abstract
Regulation of protein synthesis contributes to maintenance of homeostasis and adaptation to environmental changes. mRNA translation is controlled at various levels including initiation, elongation and termination, through post-transcriptional/translational modifications of components of the protein synthesis machinery. Recently, protein and RNA hydroxylation have emerged as important enzymatic modifications of tRNAs, elongation and termination factors, as well as ribosomal proteins. These modifications enable a correct STOP codon recognition, ensuring translational fidelity. Recent studies are starting to show that STOP codon read-through is related to the ability of the cell to cope with different types of stress, such as oxidative and chemical insults, while correlations between defects in hydroxylation of protein synthesis components and STOP codon read-through are beginning to emerge. In this review we will discuss our current knowledge of protein synthesis regulation through hydroxylation of components of the translation machinery, with special focus on STOP codon recognition. We speculate on the possibility that programmed STOP codon read-through, modulated by hydroxylation of components of the protein synthesis machinery, is part of a concerted cellular response to stress.
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Affiliation(s)
- M J Katz
- Instituto Leloir, Buenos Aires, Argentina
| | - L Gándara
- Instituto Leloir, Buenos Aires, Argentina
| | | | - P Wappner
- Instituto Leloir, Buenos Aires, Argentina.
- Departamento de Fisiología, Biología Molecular, y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
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7
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Duan J, Xu H, Guo H, O'Brochta DA, Wang F, Ma S, Zhang L, Zha X, Zhao P, Xia Q. New insights into the genomic organization and splicing of the doublesex gene, a terminal regulator of sexual differentiation in the silkworm Bombyx mori. PLoS One 2013; 8:e79703. [PMID: 24244545 PMCID: PMC3820697 DOI: 10.1371/journal.pone.0079703] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 09/24/2013] [Indexed: 11/18/2022] Open
Abstract
Sex-determination mechanisms differ among organisms. The primary mechanism is diverse, whereas the terminal regulator is relatively-conserved. We analyzed the transcripts of the Bombyx mori doublesex gene (Bmdsx), and reported novel results concerning the genomic organization and expression of Bmdsx. Bmdsx consists of nine exons and eight introns, of which two exons are novel and have not been reported previously. Bmdsx transcripts are spliced to generate seventeen alternatively-spliced forms and eleven putative trans-spliced variants. Thirteen of the alternatively-spliced forms and five of the putative trans-spliced forms are reported here for the first time. Sequence analysis predicts that ten female-specific, six male-specific splice forms and one splice form found in males and females will result in four female-specific, two male-specific Dsx proteins and one Dsx protein common to males and females. The Dsx proteins are expected to be functional and regulate downstream target genes. Some of the predicted Dsx proteins are described here for the first time. Therefore the expression of the dsx gene in B. mori results in a variety of cis- and trans-spliced transcripts and multiple Dsx proteins. These findings show that in B. mori there is a complicated pattern of dsx splicing, and that the regulation of splicing and sex-specific functions of lepidopteran dsx have evolved complexity.
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Affiliation(s)
- Jianping Duan
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
- Henan Provincial Key Laboratory of Funiu Mountain Insect Biology, Nanyang Normal University, Nanyang, PR China
| | - Hanfu Xu
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
| | - Huizhen Guo
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
| | - David A. O'Brochta
- Department of Entomology, University of Maryland, College Park, United States of America
| | - Feng Wang
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
| | - Sanyuan Ma
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
| | - Liying Zhang
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
| | - Xingfu Zha
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
| | - Ping Zhao
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
| | - Qingyou Xia
- State Key Laboratory of Silkworm Genome Biology (Southwest University), Chongqing, PR China
- * E-mail:
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8
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Vargas DY, Shah K, Batish M, Levandoski M, Sinha S, Marras SAE, Schedl P, Tyagi S. Single-molecule imaging of transcriptionally coupled and uncoupled splicing. Cell 2012; 147:1054-65. [PMID: 22118462 DOI: 10.1016/j.cell.2011.10.024] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2010] [Revised: 06/28/2011] [Accepted: 10/24/2011] [Indexed: 12/18/2022]
Abstract
Introns are removed from pre-mRNAs during transcription while the pre-mRNA is still tethered to the gene locus via RNA polymerase. However, during alternative splicing, it is important that splicing be deferred until all of the exons and introns involved in the choice have been synthesized. We have developed an in situ RNA imaging method with single-molecule sensitivity to define the intracellular sites of splicing. Using this approach, we found that the normally tight coupling between transcription and splicing is broken in situations where the intron's polypyrimidine tract is sequestered within strong secondary structures. We also found that in two cases of alternative splicing, in which certain exons are skipped due to the activity of the RNA-binding proteins Sxl and PTB, splicing is uncoupled from transcription. This uncoupling occurs only on the perturbed introns, whereas the preceding and succeeding introns are removed cotranscriptionally. PAPERCLIP:
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Affiliation(s)
- Diana Y Vargas
- Public Health Research Institute, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103, USA
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9
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The translation initiation factor eIF4E regulates the sex-specific expression of the master switch gene Sxl in Drosophila melanogaster. PLoS Genet 2011; 7:e1002185. [PMID: 21829374 PMCID: PMC3145617 DOI: 10.1371/journal.pgen.1002185] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2010] [Accepted: 05/20/2011] [Indexed: 11/27/2022] Open
Abstract
In female fruit flies, Sex-lethal (Sxl) turns off the X chromosome dosage compensation system by a mechanism involving a combination of alternative splicing and translational repression of the male specific lethal-2 (msl-2) mRNA. A genetic screen identified the translation initiation factor eif4e as a gene that acts together with Sxl to repress expression of the Msl-2 protein. However, eif4e is not required for Sxl mediated repression of msl-2 mRNA translation. Instead, eif4e functions as a co-factor in Sxl-dependent female-specific alternative splicing of msl-2 and also Sxl pre-mRNAs. Like other factors required for Sxl regulation of splicing, eif4e shows maternal-effect female-lethal interactions with Sxl. This female lethality can be enhanced by mutations in other co-factors that promote female-specific splicing and is caused by a failure to properly activate the Sxl-positive autoregulatory feedback loop in early embryos. In this feedback loop Sxl proteins promote their own synthesis by directing the female-specific alternative splicing of Sxl-Pm pre-mRNAs. Analysis of pre-mRNA splicing when eif4e activity is compromised demonstrates that Sxl-dependent female-specific splicing of both Sxl-Pm and msl-2 pre-mRNAs requires eif4e activity. Consistent with a direct involvement in Sxl-dependent alternative splicing, eIF4E is associated with unspliced Sxl-Pm pre-mRNAs and is found in complexes that contain early acting splicing factors—the U1/U2 snRNP protein Sans-fils (Snf), the U1 snRNP protein U1-70k, U2AF38, U2AF50, and the Wilms' Tumor 1 Associated Protein Fl(2)d—that have been directly implicated in Sxl splicing regulation. Gene expression in eukaryotes is a complex process that occurs in several discrete steps. Some of those steps are separated into different sub-cellular compartments and thus might be expected to occur independently of one another and involve entirely distinct factors. For example pre-mRNA splicing takes place in the nucleus where it is coupled with transcription, while mRNA translation requires export to the cytoplasm and ribosome loading. We describe studies on the fruit fly Drosophila which indicate that a cytoplasmic translation initiation factor, the cap binding protein eIF4E, plays a key role in alternative splicing in the nucleus. When eIF4E activity is compromised, we observe defects in sex-specific splicing of pre-mRNAs that are regulated by the sex determination master switch gene Sex-lethal. Our data argue that eIF4E likely plays a direct role in the regulation of alternative splicing by Sex-lethal.
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10
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Kearse MG, Chen AS, Ware VC. Expression of ribosomal protein L22e family members in Drosophila melanogaster: rpL22-like is differentially expressed and alternatively spliced. Nucleic Acids Res 2010; 39:2701-16. [PMID: 21138957 PMCID: PMC3074143 DOI: 10.1093/nar/gkq1218] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Several ribosomal protein families contain paralogues whose roles may be equivalent or specialized to include extra-ribosomal functions. RpL22e family members rpL22 and rpL22-like are differentially expressed in Drosophila melanogaster: rpL22-like mRNA is gonad specific whereas rpL22 is expressed ubiquitously, suggesting distinctive paralogue functions. To determine if RpL22-like has a divergent role in gonads, rpL22-like expression was analysed by qRT-PCR and western blots, respectively, showing enrichment of rpL22-like mRNA and a 34 kDa (predicted) protein in testis, but not in ovary. Immunohistochemistry of the reproductive tract corroborated testis-specific expression. RpL22-like detection in 80S/polysome fractions from males establishes a role for this tissue-specific paralogue as a ribosomal component. Unpredictably, expression profiles revealed a low abundant, alternative mRNA variant (designated 'rpL22-like short') that would encode a novel protein lacking the C-terminal ribosomal protein signature but retaining part of the N-terminal domain. This variant results from splicing of a retained intron (defined by non-canonical splice sites) within rpL22-like mRNA. Polysome association and detection of a low abundant 13.5 kDa (predicted) protein in testis extracts suggests variant mRNA translation. Collectively, our data show that alternative splicing of rpL22-like generates structurally distinct protein products: ribosomal component RpL22-like and a novel protein with a role distinct from RpL22-like.
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Affiliation(s)
| | | | - Vassie C. Ware
- *To whom correspondence should be addressed. Tel: +610 758 3690; Fax: +610 758 4004;
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11
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Wang Z, Lin H. Sex-lethal is a target of Bruno-mediated translational repression in promoting the differentiation of stem cell progeny during Drosophila oogenesis. Dev Biol 2006; 302:160-8. [PMID: 17067567 PMCID: PMC1904479 DOI: 10.1016/j.ydbio.2006.09.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 08/27/2006] [Accepted: 09/07/2006] [Indexed: 10/24/2022]
Abstract
The RNA Recognition Motif (RRM) type RNA binding protein Bruno is required for the differentiation of cystoblasts, the committed daughters of germline stem cells in the Drosophila ovary. To understand how Bruno controls cystoblast differentiation, we used a bioinformatics approach to identify potential mRNA targets of Bruno. One such target is the Sex-lethal (Sxl) transcript MS11, which contains four Bruno Response Elements (BREs) in its 3' untranslated region. Electrophoresis mobility shift assays demonstrated that Bruno specifically binds to the BREs of Sxl MS11 mRNA. Tagged transgenic Sxl MS11 cDNA constructs were used to show that Bruno represses the translation of the Sxl MS11 mRNA via the BRE-containing region in the 3'UTR. The lack of either Bruno or the BRE-containing region leads to overexpression of SXL, which in turn causes defects in cystoblast differentiation similar to the Bruno mutant phenotype. Therefore, Sxl MS11 represents a novel target of Bruno-mediated translational repression required for cystoblast differentiation.
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Affiliation(s)
- Zhong Wang
- Department of Cell Biology, Duke University Medical School, Durham, NC 27710, USA
- Current Address: Institute for Genome Science & Policy, Durham, NC 27708, USA
| | - Haifan Lin
- Department of Cell Biology, Duke University Medical School, Durham, NC 27710, USA
- Current Address: Yale Stem Cell Center, Yale University School of Medicine, CT 06510, USA
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Niimi T, Sahara K, Oshima H, Yasukochi Y, Ikeo K, Traut W. Molecular cloning and chromosomal localization of the Bombyx Sex-lethal gene. Genome 2006; 49:263-8. [PMID: 16604109 DOI: 10.1139/g05-108] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We cloned Bm-Sxl, an orthologue of the Drosophila melanogaster Sex-lethal (Sxl) gene from embryos of Bombyx mori. The full-length cDNAs were of 2 sizes, 1528 and 1339 bp, and were named Bm-Sxl-L and Bm-Sxl-S, respectively. Bm-Sxl-L consists of 8 exons and spans more than 20 kb of genomic DNA. The open reading frame (ORF) codes for a protein 336 amino acids in length. Bm-Sxl-S is a splice variant that lacks the second exon. This creates a new translation start 138 nucleotides downstream and an ORF that codes for 46 amino acids fewer at the N-terminus. Linkage analysis using an F2 panel mapped Bm-Sxl to linkage group 16 at 69.8 cM. We isolated 2 BACs that include the Bm-Sxl gene. With BAC-FISH we located Bm-Sxl cytogenetically on the chromosome corresponding to linkage group 16 (LG16) at position >68.8 cM.
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Affiliation(s)
- Teruyuki Niimi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
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13
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Traut W, Niimi T, Ikeo K, Sahara K. Phylogeny of the sex-determining gene Sex-lethal in insects. Genome 2006; 49:254-62. [PMID: 16604108 DOI: 10.1139/g05-107] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Sex-lethal (SXL) protein belongs to the family of RNA-binding proteins and is involved in the regulation of pre-mRNA splicing. SXL has undergone an obvious change of function during the evolution of the insect clade. The gene has acquired a pivotal role in the sex-determining pathway of Drosophila, although it does not act as a sex determiner in non-drosophilids. We collected SXL sequences of insect species ranging from the pea aphid (Acyrtho siphom pisum) to Drosophila melanogaster by searching published articles, sequencing cDNAs, and exploiting homology searches in public EST and whole-genome databases. The SXL protein has moderately conserved N- and C-terminal regions and a well-conserved central region including 2 RNA recognition motifs. Our phylogenetic analysis shows that a single orthologue of the Drosophila Sex-lethal (Sxl) gene is present in the genomes of the malaria mosquito Anopheles gambiae, the honeybee Apis mellifera, the silkworm Bombyx mori, and the red flour beetle Tribolium castaneum. The D. melanogaster, D. erecta, and D. pseudoobscura genomes, however, contain 2 paralogous genes, Sxl and CG3056, which are orthologous to the Anopheles, Apis, Bombyx, and Tribolium Sxl. Hence, a duplication in the fly clade generated Sxl and CG3056. Our hypothesis maintains that one of the genes, Sxl, adopted the new function of sex determiner in Drosophila, whereas the other, CG3056, continued to serve some or all of the yet-unknown ancestral functions.
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Affiliation(s)
- Walther Traut
- Institut für Biologie, Universität zu Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany.
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Gawande B, Robida MD, Rahn A, Singh R. Drosophila Sex-lethal protein mediates polyadenylation switching in the female germline. EMBO J 2006; 25:1263-72. [PMID: 16511567 PMCID: PMC1422161 DOI: 10.1038/sj.emboj.7601022] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2005] [Accepted: 02/02/2006] [Indexed: 01/16/2023] Open
Abstract
The Drosophila master sex-switch protein Sex-lethal (SXL) regulates the splicing and/or translation of three known targets to mediate somatic sexual differentiation. Genetic studies suggest that additional target(s) of SXL exist, particularly in the female germline. Surprisingly, our detailed molecular characterization of a new potential target of SXL, enhancer of rudimentary (e(r)), reveals that SXL regulates e(r) by a novel mechanism--polyadenylation switching--specifically in the female germline. SXL binds to multiple SXL-binding sites, which include the GU-rich poly(A) enhancer, and competes for the binding of CstF64 in vitro. The SXL-binding sites are able to confer sex-specific poly(A) switching onto an otherwise nonresponsive polyadenylation signal in vivo. The sex-specific poly(A) switching of e(r) provides a means for translational regulation in germ cells. We present a model for the SXL-dependent poly(A) site choice in the female germline.
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Affiliation(s)
- Bharat Gawande
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
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15
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Louis M, Holm L, Sánchez L, Kaufman M. A Theoretical Model for the Regulation of Sex-lethal, a Gene That Controls Sex Determination and Dosage Compensation in Drosophila melanogaster. Genetics 2003; 165:1355-84. [PMID: 14668388 PMCID: PMC1462829 DOI: 10.1093/genetics/165.3.1355] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Cell fate commitment relies upon making a choice between different developmental pathways and subsequently remembering that choice. Experimental studies have thoroughly investigated this central theme in biology for sex determination. In the somatic cells of Drosophila melanogaster, Sex-lethal (Sxl) is the master regulatory gene that specifies sexual identity. We have developed a theoretical model for the initial sex-specific regulation of Sxl expression. The model is based on the well-documented molecular details of the system and uses a stochastic formulation of transcription. Numerical simulations allow quantitative assessment of the role of different regulatory mechanisms in achieving a robust switch. We establish on a formal basis that the autoregulatory loop involved in the alternative splicing of Sxl primary transcripts generates an all-or-none bistable behavior and constitutes an efficient stabilization and memorization device. The model indicates that production of a small amount of early Sxl proteins leaves the autoregulatory loop in its off state. Numerical simulations of mutant genotypes enable us to reproduce and explain the phenotypic effects of perturbations induced in the dosage of genes whose products participate in the early Sxl promoter activation.
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Affiliation(s)
- Matthieu Louis
- The European Bioinformatics Institute, EMBL Outstation, Cambridge CB10 1SD, United Kingdom.
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16
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Förch P, Valcárcel J. Splicing regulation in Drosophila sex determination. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2003; 31:127-51. [PMID: 12494765 DOI: 10.1007/978-3-662-09728-1_5] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- P Förch
- Gene Expression Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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17
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Sievert V, Kuhn S, Paululat A, Traut W. Sequence conservation and expression of the sex-lethal homologue in the fly Megaselia scalaris. Genome 2000; 43:382-90. [PMID: 10791828 DOI: 10.1139/g99-132] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sex-lethal (Sxl) is Drosophila melanogaster's key regulating gene in the sex-determining cascade. Its homologue in Megaselia scalaris, the chromosome 3 gene Megsxl, codes for a protein with an overall similarity of 77% with the corresponding D. melanogaster sequence. Expression in M. scalaris, however, is very unlike that in D. melanogaster. Megsxl transcripts with a long ORF occur in both sexes. Differential splicing is conserved but not sex-specific. There are several splice variants, among them one is common to gonads and somatic tissues of all developmental stages investigated, one is specific for ovaries and embryos, and a third one is not found in ovaries. In the ovary, Megsxl is heavily transcribed in nurse cells and transported into eggs. These results suggest a non-sex-determining function during early embryogenesis; the presence of Megsxl RNA in testes and somatic tissues calls for other (or more) functions.
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Affiliation(s)
- V Sievert
- Institut für Biologie, Medizinische Universität Lübeck, Germany
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18
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Bhattacharya A, Sudha S, Chandra HS, Steward R. flex, an X-linked female-lethal mutation in Drosophila melanogaster controls the expression of Sex-lethal. Development 1999; 126:5485-93. [PMID: 10556072 DOI: 10.1242/dev.126.23.5485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Sex-lethal (Sxl) gene is required in Drosophila females for sexual differentiation of the soma, for gem cell differentiation and dosage compensation. We have isolated three new alleles of female-lethal-on-X (flex), an X-linked female-lethal mutation and have characterized its function in sex determination. SXL protein is missing in flex/flex embryos, however transcription from both Sxl(Pe), the early Sxl promoter and Sxl(Pm), the late maintenance promoter, is normal in flex homozygotes. In flex/flex embryos, Sxl mRNA is spliced in the male mode. Analysis of flex germline clones shows that it also functions in oogenesis, but in contrast to Sxl mutants that show an early arrest tumorous phenotype, flex mutant egg chambers develop to stage 10. In flex ovarian clones, Sxl RNA is also spliced in the male form. Hence, flex is a sex-specific regulator of Sxl functioning in both the soma and the germline. Genetic interaction studies show that flex does not enhance female lethality of Sxl loss-of-function alleles but it rescues the male-specific lethality of both of the gain-of-function Sxl mutations, Sxl(M1)and Sxl(M4.) In contrast to mutations in splicing regulators of Sxl, the female lethality of flex is not rescued by either Sxl(M1)or Sxl(M4). Based on these observations, we propose that flex regulates Sxl at a post-splicing stage and regulates either its translation or the stability of the SXL protein.
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Affiliation(s)
- A Bhattacharya
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560 012, India
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19
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Sahara S, Aoto M, Eguchi Y, Imamoto N, Yoneda Y, Tsujimoto Y. Acinus is a caspase-3-activated protein required for apoptotic chromatin condensation. Nature 1999; 401:168-73. [PMID: 10490026 DOI: 10.1038/43678] [Citation(s) in RCA: 315] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Apoptosis is defined by several unique morphological nuclear changes, such as chromatin condensation and nuclear fragmentation. These changes are triggered by the activation of a family of cysteine proteases called caspases, and caspase-activated DNase (CAD/DFF40) and lamin protease (caspase-6) have been implicated in some of these changes. CAD/DFF40 induces chromatin condensation in purified nuclei, but distinct caspase-activated factor(s) may be responsible for chromatin condensation. Here we use an in vitro system to identify a new nuclear factor, designated Acinus, which induces apoptotic chromatin condensation after cleavage by caspase-3 without inducing DNA fragmentation. Immunodepletion experiments showed that Acinus is essential for apoptotic chromatin condensation in vitro, and an antisense study revealed that Acinus is also important in the induction of apoptotic chromatin condensation in cells.
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Affiliation(s)
- S Sahara
- Department of Medical Genetics, Biomedical Research Center, Osaka University Medical School, Suita, Japan
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20
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Deshpande G, Calhoun G, Schedl PD. The N-terminal domain of Sxl protein disrupts Sxl autoregulation in females and promotes female-specific splicing of tra in males. Development 1999; 126:2841-53. [PMID: 10357929 DOI: 10.1242/dev.126.13.2841] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sex determination in Drosophila depends upon the post-transcriptional regulatory activities of the Sex-lethal (Sxl) gene. Sxl maintains the female determined state and activates female differentiation pathways by directing the female-specific splicing of Sxl and tra pre-mRNAs. While there is compelling evidence that Sxl proteins regulate splicing by directly binding to target RNAs, previous studies indicate that the two Sxl RNA-binding domains are not in themselves sufficient for biological activity and that an intact N-terminal domain is also critical for splicing function. To further investigate the functions of the Sxl N terminus, we ectopically expressed a chimeric protein consisting of the N-terminal 99 amino acids fused to ss-galactosidase. The Nss-gal fusion protein behaves like a dominant negative, interfering with the Sxl autoregulatory feedback loop and killing females. This dominant negative activity can be attributed to the recruitment of the fusion protein into the large Sxl:Snf splicing complexes that are found in vivo and the consequent disruption of these complexes. In addition to the dominant negative activity, the Nss-gal fusion protein has a novel gain-of-function activity in males: it promotes the female-specific processing of tra pre-mRNAs. This novel activity is discussed in light of the blockage model for the tra splicing regulation.
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Affiliation(s)
- G Deshpande
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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21
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Saccone G, Peluso I, Artiaco D, Giordano E, Bopp D, Polito LC. The Ceratitis capitata homologue of the Drosophila sex-determining gene sex-lethal is structurally conserved, but not sex-specifically regulated. Development 1998; 125:1495-500. [PMID: 9502730 DOI: 10.1242/dev.125.8.1495] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Drosophila, Sxl functions as a binary switch in sex determination. Under the control of the primary sex-determining signal, it produces functional protein only in XX animals to implement female development. Here we report that, in contrast to Drosophila, the Sxl homologue in the Medfly, Ceratitis capitata, expresses the same mRNAs and protein isoforms in both XX and XY animals irrespective of the primary sex-determining signal. Also, experiments with two inducible transgenes demonstrate that the corresponding Ceratitis SXL product has no significant sex-transforming effects when expressed in Drosophila. Similar results have been obtained for the Sxl homologue of Musca domestica (Meise, M., Hilfiker-Kleiner, D., Brunner, C., DLbendorfer, A., N?thiger, R. and Bopp, D. (1998) Development 125, 1487–1494). Our findings suggest that Sxl acquired its master regulatory role in sex determination during evolution of the Acalyptratae group, most probably after phylogenetic divergence of the genus Drosophila from other genera of this group.
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Affiliation(s)
- G Saccone
- Dipartimento di Genetica, Biologia generale e Moleculare, Universitá degli Studi di Napoli 'Federico II', Napoli, Italy.
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22
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Meise M, Hilfiker-Kleiner D, Dübendorfer A, Brunner C, Nöthiger R, Bopp D. Sex-lethal, the master sex-determining gene in Drosophila, is not sex-specifically regulated in Musca domestica. Development 1998; 125:1487-94. [PMID: 9502729 DOI: 10.1242/dev.125.8.1487] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sex-lethal (Sxl) is the master switch gene for somatic sex determination in Drosophila melanogaster. In XX animals, Sxl becomes activated and imposes female development; in X(Y) animals, Sxl remains inactive and male development ensues. A switch gene for sex determination, called F, has also been identified in the housefly, Musca domestica. An active F dictates female development, while male development ensues when F is inactive. To test if the switch functions of Sxl and F are founded on a common molecular basis, we isolated the homologous Sxl gene in the housefly. Though highly conserved in sequence, Musca-Sxl is not sex-specifically regulated: the same transcripts and protein isoforms are expressed in both male and female animals throughout development. Musca-Sxl is apparently not controlled by the primary sex-determining signal and, thus, is unlikely to correspond to the F gene. Ectopic expression of Musca-SXL protein in Drosophila does not exert any noticeable effects on the known target genes of endogenous Sxl. Instead, forced overexpression of the transgene eventually results in lethality of both XY and XX animals and in developmental abnormalities in some escaper XY animals. Similar results were obtained with the Sxl homologue of Ceratitis capitata (Saccone, G., Peluso, I., Artiaco, D., Giodano, E., Bopp, D. and Polito, L. C. (1998) Development 125, 1495–1500) suggesting that, in these non-drosophilid species, Sxl performs a function different from that in sex determination.
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Affiliation(s)
- M Meise
- Zoological Institute, University of Zürich-Irchel, Zürich, Switzerland
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23
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Wang J, Dong Z, Bell LR. Sex-lethal interactions with protein and RNA. Roles of glycine-rich and RNA binding domains. J Biol Chem 1997; 272:22227-35. [PMID: 9268369 DOI: 10.1074/jbc.272.35.22227] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Sex-lethal (Sxl) is an RNA-binding protein, containing two conserved RNA binding domains (RBDs) and a glycine-rich region, which functions as a regulator of alternative splicing in Drosophila sex determination. Previous work demonstrated that Sxl monomers interact cooperatively upon binding to target RNAs and that the cooperativity depends on the glycine-rich N terminus. Here we use band shift experiments to show that RNA binding patterns are altered when Sxl is combined with other proteins having similar glycine-rich domains, including mammalian heterogeneous nuclear (hn) RNP L and Drosophila Hrb87F (an hnRNP A/B homolog). Direct involvement of the Sxl glycine-rich region in protein interactions was verified by Far-Western analysis. Two interaction domains, the Sxl N terminus and the Sxl first RNA binding domain, were suggested by the yeast two-hybrid assay. In a systematic examination of the RNA binding properties of Sxl domains, it was found that the Sxl termini as well as the RBDs influence RNA binding specificity. Finally, selection of the Sxl optimal binding site (SELEX) confirms the importance of U-runs in the Sxl binding site and suggests a second type of non-U-run target that may be associated with RNA secondary structure.
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Affiliation(s)
- J Wang
- Molecular Biology Program, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-1340, USA
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24
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Penalva LO, Sakamoto H, Navarro-Sabaté A, Sakashita E, Granadino B, Segarra C, Sánchez L. Regulation of the gene Sex-lethal: a comparative analysis of Drosophila melanogaster and Drosophila subobscura. Genetics 1996; 144:1653-64. [PMID: 8978052 PMCID: PMC1207716 DOI: 10.1093/genetics/144.4.1653] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The Drosophila gene Sex-lethal (Sxl) controls the processes of sex determination and dosage compensation. A Drosophila subobscura genomic fragment containing all the exons and the late and early promotors in the Sxl gene of D. melanogaster was isolated. Early Sxl expression in D. subobscura seems to be controlled at the transcriptional level, possibly by the X:A signal. In the region upstream of the early Sxl transcription initiation site are two conserved regions suggested to be involved in the early activation of Sxl. Late Sxl expression in D. subobscura produces four transcripts in adult females and males. In males, the transcripts have an additional exon which contains three translational stop codons so that a truncated, presumably nonfunctional Sxl protein is produced. The Sxl pre-mRNA of D. subobscura lacks the poly-U sequence presented at the polypirimidine tract of the 3' splice site of the male-specific exon present in D. melanogaster. Introns 2 and 3 contain the Sxl-binding poly-U stretches, whose localization in intron 2 varies but in intron 3 is conserved. The Sxl protein is fully conserved at the amino acid level in both species.
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Affiliation(s)
- L O Penalva
- Centro de Investigaciones Biológicas (C.S.I.C.), Madrid, Spain
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25
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Müller-Holtkamp F. The Sex-lethal gene homologue in Chrysomya rufifacies is highly conserved in sequence and exon-intron organization. J Mol Evol 1995; 41:467-77. [PMID: 7563134 DOI: 10.1007/bf00160318] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A great variety of sex determination mechanisms exists in insect species. In Drosophila melanogaster sex is determined by the ratio between X chromosomes and autosomes, while in the blowfly Chrysomya rufifacies it is maternally determined. A cascade of genes which are involved in sex determination has been identified in D. melanogaster with the Sex-lethal gene (Sxl) as the key gene. We screened genomic libraries of C. rufifacies with a probe of the Sxl gene from D. melanogaster and isolated a genomic region that included most of the homologous gene. DNA- and protein-sequence comparison showed a high percent identity between the Chrysomya and the Drosophila gene. Up to 90% identity of the amino acid sequences was found in the region that contained the RNA-binding domains. The degree of identity is much lower outside of this functionally important region (18% identity). cDNA analysis showed a highly conserved exon-intron structure between the two species, although sex-specific splicing as used in D. melanogaster for the regulation of Sxl activity, could not be detected in C. rufifacies.
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26
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Kelley RL, Solovyeva I, Lyman LM, Richman R, Solovyev V, Kuroda MI. Expression of msl-2 causes assembly of dosage compensation regulators on the X chromosomes and female lethality in Drosophila. Cell 1995; 81:867-77. [PMID: 7781064 DOI: 10.1016/0092-8674(95)90007-1] [Citation(s) in RCA: 254] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Male-specific lethal-2 (msl-2) is a RING finger protein that is required for X chromosome dosage compensation in Drosophila males. Consistent with the formation of a dosage compensation protein complex, msl-2 colocalizes with the other MSL proteins on the male X chromosome and coimmunoprecipitates with msl-1 from male larval extracts. Ectopic expression of msl-2 in females results in the appearance of the other MSL dosage compensation regulators on the female X chromosomes and decreased female viability. We suggest that msl-2 RNA is the primary target of SxI regulation in the dosage compensation pathway and present a speculative model for the regulation of two distinct modes of dosage compensation by SxI.
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Affiliation(s)
- R L Kelley
- Howard Hughes Medical Institute, Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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27
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Bernstein M, Lersch RA, Subrahmanyan L, Cline TW. Transposon insertions causing constitutive Sex-lethal activity in Drosophila melanogaster affect Sxl sex-specific transcript splicing. Genetics 1995; 139:631-48. [PMID: 7713421 PMCID: PMC1206370 DOI: 10.1093/genetics/139.2.631] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Sex-lethal (Sxl) gene products induce female development in Drosophila melanogaster and suppress the transcriptional hyperactivation of X-linked genes responsible for male X-chromosome dosage compensation. Control of Sxl functioning by the dose of X-chromosomes normally ensures that the female-specific functions of this developmental switch gene are only expressed in diplo-X individuals. Although the immediate effect of X-chromosome dose is on Sxl transcription, during most of the life cycle "on" vs. "off" reflects alternative Sxl RNA splicing, with the female (productive) splicing mode maintained by a positive feedback activity of SXL protein on Sxl pre-mRNA splicing. "Male-lethal" (SxlM) gain-of-function alleles subvert Sxl control by X-chromosome dose, allowing female Sxl functions to be expressed independent of the positive regulators upstream of Sxl. As a consequence, SxlM haplo-X animals (chromosomal males) die because of improper dosage compensation, and SxlM chromosomal females survive the otherwise lethal effects of mutations in upstream positive regulators. Five independent spontaneous SxlM alleles were shown previously to be transposon insertions into what was subsequently found to be the region of regulated sex-specific Sxl RNA splicing. We show that these five alleles represent three different mutant types: SxlM1, SxlM3, and SxlM4. SxlM1 is an insertion of a roo element 674 bp downstream of the translation-terminating male-specific exon. SxlM3 is an insertion of a hobo transposon (not 297 as previously reported) into the 3' splice site of the male exon, and SxlM4 is an insertion of a novel transposon into the male-specific exon itself. We show that these three gain-of-function mutants differ considerably in their ability to bypass the sex determination signal, with SxlM4 being the strongest and SxlM1 the weakest. This difference is also reflected in effects of these mutations on sex-specific RNA splicing and on the rate of appearance of SXL protein in male embryos. Transcript analysis of double-mutant male-viable SxlM derivatives in which the SxlM insertion is cis to loss-of-function mutations, combined with other results reported here, indicates that the constitutive character of these SxlM alleles is a consequence of an alteration of the structure of the pre-mRNA that allows some level of female splicing to occur even in the absence of functional SXL protein. Surprisingly, however, most of the constitutive character of SxlM alleles appears to depend on the mutant alleles' responsiveness, perhaps greater than wild-type, to the autoregulatory splicing activity of the wild-type SXL proteins they produce.
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Affiliation(s)
- M Bernstein
- Department of Biology, Princeton University, New Jersey 08544, USA
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28
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Brady JP, Kantorow M, Sax CM, Donovan DM, Piatigorsky J. Murine transcription factor alpha A-crystallin binding protein I. Complete sequence, gene structure, expression, and functional inhibition via antisense RNA. J Biol Chem 1995; 270:1221-9. [PMID: 7836383 DOI: 10.1074/jbc.270.3.1221] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
alpha A-crystallin binding protein I (alpha A-CRYBP1) is a ubiquitously expressed DNA binding protein that was previously identified by its ability to interact with a functionally important sequence in the mouse alpha A-crystallin gene promoter. Here, we have cloned a single copy gene with 10 exons spanning greater than 70 kb of genomic DNA that encodes alpha A-CRYBP1. The mouse alpha A-CRYBP1 gene specifies a 2,688-amino acid protein with 72% amino acid identity to its human homologue, PRDII-BF1. Both the human and the mouse proteins contain two sets of consensus C2H2 zinc fingers at each end as well a central nonconsensus zinc finger. The alpha A-CRYBP1 gene produces a 9.5-kb transcript in 11 different tissues as well as a testis-specific, 7.7-kb transcript. alpha A-CRYBP1 cDNA clones were isolated from adult mouse brain and testis as well as from cell lines derived from mouse lens (alpha TN4-1) and muscle (C2C12). A single clone isolated from the muscle C2C12 library contains an additional exon near the 5'-end that would prevent production of a functional protein if the normal translation start site were utilized; however, there is another potential initiation codon located downstream that is in frame with the rest of the coding region. In addition, we identified multiple cDNAs from the testis in which the final intron is still present. Finally, we used an antisense expression construct derived from an alpha A-CRYBP1 cDNA clone to provide the first functional evidence that alpha A-CRYBP1 regulates gene expression. When introduced into the alpha TN4-1 mouse lens cell line, the antisense construct significantly inhibited expression from a heterologous promoter that utilized the alpha A-CRYBP1 binding site as an enhancer.
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Affiliation(s)
- J P Brady
- Laboratory of Molecular and Developmental Biology, NEI, National Institutes of Health, Bethesda, Maryland 20892
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29
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Abstract
Certain female-sterile mutations in Drosophila result in the uncontrolled proliferation of X/X germ cells. It has been proposed that this ovarian tumor phenotype results from the sexual transformation of X/X germ cells to a male identity. We present findings inconsistent with this model. We demonstrate that the tumorous cells produced by mutations in the ovarian tumor (otu), Sex-lethal (Sxl) and sans fille (snf) genes are capable of female-specific transcription and RNA processing. This indicates that these ovarian tumor cells still retain some female identity. Therefore, we propose that mutations in these genes do not cause a male transformation of the X/X germ line but instead either cause an ambiguous sexual identity or block specific stages of oogenesis. Our findings indicate that while Sxl is the master sex determination gene in somatic cells, it appears to play a more subsidiary role in the germ line. Finally, we demonstrate that the germ line function of Sxl depends on the activity of a specific OTU isoform.
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Affiliation(s)
- E Bae
- Department of Biological Sciences, University of Iowa, Iowa City 52242-1234
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30
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Bernstein M, Cline TW. Differential effects of Sex-lethal mutations on dosage compensation early in Drosophila development. Genetics 1994; 136:1051-61. [PMID: 8005414 PMCID: PMC1205862 DOI: 10.1093/genetics/136.3.1051] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In response to the primary sex determination signal, X chromosome dose, the Sex-lethal gene controls all aspects of somatic sex determination and differentiation, including X chromosome dosage compensation. Two complementary classes of mutations have been identified that differentially affect Sxl somatic functions: (1) those impairing the "early" function used to set developmental pathway choice in response to the sex determination signal and (2) those impairing "late" functions involved in maintaining the pathway choice independent of the initiating signal and/or in directing differentiation. This "early vs. late" distinction correlates with a switch in promoter utilization from SxlPe to SxlPm at the blastoderm stage and a corresponding switch from transcriptional to RNA splicing control. Here we characterize five partial-loss-of-function Sxl alleles to explore a distinction between "early vs. late" functioning of Sxl in dosage compensation. Assaying for dosage compensation during the blastoderm stage, we find that the earliest phase of the dosage compensation process is controlled by products of the early Sxl promoter, SxlPe. Hence, in addition to triggering the sexual pathway decision of cells, products derived from SxlPe also control early dosage compensation, the first manifestation of sexually dimorphic differentiation. The effects of mutant Sxl alleles on early dosage compensation are consistent with their previous categorization as early vs. late defective with respect to their effects on pathway initiation. Results reported here suggest that the dosage compensation regulatory genes currently known to function downstream of Sxl, genes known as the "male-specific lethals," do not control all aspects of dosage compensation either at the blastoderm stage or later in development. In the course of this study, we also discovered that the canonical early defective allele, Sxlf9, which is impaired in its ability to establish the female developmental pathway commitment, is likely to be defective in the stability and/or functioning of products derived from SxlPe, rather than in the ability of SxlPe to respond to the chromosomal sex determination signal.
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Affiliation(s)
- M Bernstein
- Department of Biology, Princeton University, New Jersey 08544
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31
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Hodges D, Bernstein SI. Genetic and biochemical analysis of alternative RNA splicing. ADVANCES IN GENETICS 1994; 31:207-81. [PMID: 8036995 DOI: 10.1016/s0065-2660(08)60399-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- D Hodges
- Biology Department, San Diego State University, California 92182-0057
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McElreavey K, Vilain E, Cotinot C, Payen E, Fellous M. Control of sex determination in animals. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 218:769-83. [PMID: 8281929 DOI: 10.1111/j.1432-1033.1993.tb18432.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- K McElreavey
- Institut Nationale de la Santé et de la Recherche Médicale (INSERM) U276, Université Paris VII, Institut Pasteur, France
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Pauli D, Oliver B, Mahowald AP. The role of the ovarian tumor locus in Drosophila melanogaster germ line sex determination. Development 1993; 119:123-34. [PMID: 8275850 DOI: 10.1242/dev.119.1.123] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The locus ovarian tumor (otu) is involved in several aspects of oogenesis in Drosophila melanogaster. The possible role of otu in the determination of the sexual identity of germ cells has not been extensively explored. Some otu alleles produce a phenotype known as ovarian tumors: ovarioles are filled with numerous poorly differentiated germ cells. We show that these mutant germ cells have a morphology similar to primary spermatocytes and that they express male germ line-specific reporter genes. This indicates that they are engaged along the male pathway of germ line differentiation. Consistent with this conclusion, we found that the splicing of Sex-lethal (Sxl) pre-mRNAs occurs in the male-specific mode in otu-transformed germ cells. The position of the otu locus in the regulatory cascade of germ line sex determination has been studied by using mutations that constitutively express the feminizing activity of the Sxl gene. The sexual transformation of the germ cells observed with several combinations of otu alleles can be reversed by constitutive expression of Sxl. This shows that otu acts upstream of Sxl in the process of germ line sex determination. Other phenotypes of otu mutations were not rescued by constitutive expression of Sxl, suggesting that several functions of otu are likely to be independent of sex determination. Finally, we show that the gene dosage of otu modifies the phenotype of ovaries heterozygous for the dominant alleles of ovo, another gene involved in germ line sex determination. One dose of otu+ enhances the ovoD ovarian phenotypes, while three doses partially suppress these phenotypes. Synergistic interaction between ovoD1 and otu alleles leads to the occasional transformation of chromosomally female germ cells into early spermatocytes. These interactions are similar to those observed between ovoD and one allele of the sans fille (snf) locus. Altogether, our results imply that the otu locus acts, along with ovo, snf, and Sxl, in a pathway (or parallel pathways) required for proper sex determination of the female germ line.
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Affiliation(s)
- D Pauli
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106
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Bopp D, Horabin JI, Lersch RA, Cline TW, Schedl P. Expression of the Sex-lethal gene is controlled at multiple levels during Drosophila oogenesis. Development 1993; 118:797-812. [PMID: 8076518 DOI: 10.1242/dev.118.3.797] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In addition to controlling somatic sexual development in Drosophila melanogaster, the Sex-lethal (Sxl) gene is required for proper differentiation of female germ cells. To investigate its role in germ-line development, we have examined the expression of Sxl in wild-type ovaries and ovaries that are defective in early steps of germ cell differentiation. As in the soma, the basic mechanism for on/off regulation of Sxl relies on sex-specific processing of its transcripts in germ cells. One class of female-sterile mutations, which includes fs(1)1621 and the tumorous-ovary-producing allele of the ovarian tumor gene, otu1, is defective in the splicing process. These mutants have germ lines with high amounts of Sxl RNA spliced in the male mode and a severe reduction of protein levels in the germ cells. Another class of female-sterile mutations produces a phenotype similar to that seen in fs(1)1621 and otu1 but appears to express normal levels of Sxl protein in the germ cells. However, this second class does not show the changes in protein distribution normally observed in wild-type germ cells. In the wild-type germarium, the non-differentiated germ cells show a strong cytoplasmic accumulation of Sxl protein followed, as the germ cells differentiate, by a dramatic reduction and redistribution of the protein into nuclear foci. Interestingly, two female-sterile alleles of Sxl, Sxlf4 and Sxlf5 belong to the second class, which shows persistent cytoplasmic accumulation of Sxl protein. These Sxl female-sterile mutants encode an altered protein indicating that Sxl regulates processes that eventually lead to the changes in Sxl protein distribution. Lastly, we demonstrate that during the final stages of oogenesis several mechanisms must operate to prevent the progeny from inheriting Sxl protein. Conceivably, this regulation safeguards the inadvertent activation of the Sxl autoregulatory feedback loop in the male zygote.
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Affiliation(s)
- D Bopp
- Department of Molecular Biology, Moffett laboratory, Princeton University, NJ 08544
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Capel B, Swain A, Nicolis S, Hacker A, Walter M, Koopman P, Goodfellow P, Lovell-Badge R. Circular transcripts of the testis-determining gene Sry in adult mouse testis. Cell 1993; 73:1019-30. [PMID: 7684656 DOI: 10.1016/0092-8674(93)90279-y] [Citation(s) in RCA: 845] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Sry is expressed at higher levels in the adult testis, where no function has been determined, than in the genital ridge, its critical site of action. cDNA and 5' RACE clones isolated from testis or from Sry-transfected cell lines have an unusual structure, with 3' sequences located in a 5' position. RNAase protection assays and reverse transcription polymerase chain reactions confirmed that these unusual RNA molecules represent the most abundant transcript in testis. Furthermore, oligonucleotide hybridization and RNAase H digestion proved that these Sry RNA molecules are circular. Similar transcripts were detected in the testes of mice with Mus musculus musculus, Mus musculus domesticus, and Mus spretus Sry genes. The circular RNA is found in the cytoplasm but is not substantially bound to polysomes. We suggest that the circles arise from normal splicing processes as a consequence of the unusual genomic structure surrounding the Sry locus in the mouse.
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Affiliation(s)
- B Capel
- Laboratory of Eukaryotic Molecular Genetics, Medical Research Council, National Institute for Medical Research, London, England
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Yao KM, Samson ML, Reeves R, White K. Gene elav of Drosophila melanogaster: a prototype for neuronal-specific RNA binding protein gene family that is conserved in flies and humans. JOURNAL OF NEUROBIOLOGY 1993; 24:723-39. [PMID: 8331337 DOI: 10.1002/neu.480240604] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Regulated gene activity is crucial to the formation and function of the nervous system. It is well known that gene regulation can occur at the transcriptional, post-transcriptional, translational, and post-translational levels. In this review our focus has been on the post-transcriptional regulation in neurons and on neural-specific RNA binding proteins that may be involved in post-transcriptional modulation of gene activity. We have taken advantage of this opportunity to review our work on the elav gene of Drosophila melanogaster which encodes a neural-specific RNA binding protein and relate it to other members of this elav-like gene family. We report new data that suggests that elav is post-transcriptionally regulated and we demonstrate that below-threshold levels of ELAV protein severely affects neuronal differentiation.
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Affiliation(s)
- K M Yao
- Department of Biology, Brandeis University, Waltham, Massachusetts 02254
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Abstract
Sex differentiation in Drosophila is controlled by a regulatory cascade with at least three regulated alternative RNA-processing events. The results of recent work have verified much of the earlier molecular and genetic work in this field and have provided a demonstration that both positive and negative regulatory mechanisms are involved.
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Affiliation(s)
- M McKeown
- Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92186
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Keyes LN, Cline TW, Schedl P. The primary sex determination signal of Drosophila acts at the level of transcription. Cell 1992; 68:933-43. [PMID: 1547493 DOI: 10.1016/0092-8674(92)90036-c] [Citation(s) in RCA: 170] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
For Drosophila, the choice between male and female development is made by the switch gene, Sxl, in response to the X:A ratio. Once Sxl is turned on in females, it actively maintains the determined state, independent of the X:A signal, by a positive autoregulatory feedback loop in which Sxl proteins direct the female-specific splicing of Sxl transcripts. In this paper we have investigated the mechanism controlling pathway initiation. Our results suggest a two-step model for the initial activation of Sxl in females. In the first step, a special class of Sxl mRNAs is expressed in female embryos from an early promoter that responds to the genes signaling the X:A ratio. The proteins produced from these early mRNAs then initiate the autoregulatory loop by directing the female-specific processing of transcripts from the late Sxl promoter.
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Affiliation(s)
- L N Keyes
- Department of Biology, Princeton University, New Jersey 08544
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Salz HK. The genetic analysis of snf: a Drosophila sex determination gene required for activation of Sex-lethal in both the germline and the soma. Genetics 1992; 130:547-54. [PMID: 1551576 PMCID: PMC1204872 DOI: 10.1093/genetics/130.3.547] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Our analysis demonstrates that snf is a positive regulator of Sex-lethal in both the germline and the soma. In the germline, unregulated expression of Sex-lethal can bypass the requirement for snf+ gene function, implying that snf is required for Sex-lethal activity in the germline. This conclusion is supported by the finding that the Sex-lethal transcription pattern is abnormal in a snf mutant background. In the soma, activation of Sex-lethal appears to be sensitive to snf gene dosage only when the probability of Sex-lethal activation has been otherwise reduced. We also show that the activity of one of the constitutive Sex-lethal alleles (SxlM1) is sensitive to snf gene dosage, demonstrating that, in spite of its constitutive behavior in some assays, SxlM1 is still subject to some regulation. In spite of snf's role in the somatic activation of Sex-lethal, no lethal alleles of snf were isolated in a screen of approximately 25,000 chromosomes. The observation that the existing snf mutations present a lethal phenotype only in certain genetic backgrounds suggests that snf is required, but is not essential, for the activation of Sex-lethal in the soma. In contrast, snf does appear to be essential for activation of Sex-lethal in the germline, as evidenced by its female-sterile phenotype.
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Affiliation(s)
- H K Salz
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio 44106
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