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Suppressor of zeste 12, a Polycomb group gene in Drosophila melanogaster; one piece in the epigenetic puzzle
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In multicellular organisms all cells in one individual have an identical genotype, and yet their bodies consist of many and very different tissues and thus many different cell types. Somehow there must be a difference in how genes are interpreted. So, there must be signals that tell the genes when and where to be active and inactive, respectively. In some instances a specific an expression pattern (active or inactive) is epigenetic; it is established and maintained throughout multiple rounds of cell divisions. In the developing Drosophila embryo, the proper expression pattern of e.g. the homeotic genes Abd-B and Ubx is to be kept active in the posterior part and silenced in the anterior. Properly silenced homeotic genes are crucial for the correct segmentation pattern of the fly and the Polycomb group (Pc-G) proteins are vital for maintaining this type of stable repression.

As part of this thesis, Suppressor of zeste 12 (Su(z)12) is characterized as a Drosophila Pc-G gene. Mutations in the gene cause widespread misexpression of several homeotic genes in embryos and larvae. Results show that the silencing of the homeotic genes Abd-B and Ubx, probably is mediated via physical binding of SU(Z)12 to Polycomb Response Elements in the BX-C. Su(z)12 mutations are strong suppressors of position-effect-variegation and the SU(Z)12 protein binds weakly to the heterochromatic centromeric region. These results indicate that SU(Z)12 has a function in heterochromatin-mediated repression, which is an unusual feature for a Pc-G protein. The structure of the Su(z)12 gene was determined and the deduced protein contains a C2-H2 zinc finger domain, several nuclear localization signals, and a region, the VEFS box, with high homology to mammalian and plant homologues. Su(z)12 was originally isolated in a screen for modifiers of the zeste-white interaction and I present results that suggests that this effect is mediated through an interaction between Su(z)12 and zeste. I also show that Su(z)12 interact genetically with other Pc-G mutants and that the SU(Z)12 protein binds more than 100 euchromatic bands on polytene chromosomes. I also present results showing that SU(Z)12 is a subunit of two different E(Z)/ESC embryonic silencing complexes, one 1MDa and one 600 kDa complex, where the larger complex also contains PCL and RPD3.

In conclusion, results presented in this thesis show that the recently identified Pc-G gene, Su(z)12, is of vital importance for correct maintenance of silencing of the developmentally important homeotic genes.

Place, publisher, year, edition, pages
2003. , p. 52
Keywords [en]
Genetics, Drosophila melanogaster, epigenetic, homeotic genes, Polycomb group, PRE, heterochromatin, Suppressor of zeste 12, chromatin silencing
Keywords [sv]
Genetik
National Category
Medical Genetics
Research subject
Genetics
Identifiers
URN: urn:nbn:se:umu:diva-98ISBN: 91-7305-437-2 (print)OAI: oai:DiVA.org:umu-98DiVA, id: diva2:145272
Public defence
2003-05-30, Major Groove, Molekylärbilogi, Byggnad 6L, Umeå, 10:00
Opponent
Supervisors
Available from: 2003-09-10 Created: 2003-09-10 Last updated: 2019-01-24Bibliographically approved
List of papers
1. Su(z)12, a novel Drosophila Polycomb group gene that is conserved in vertebrates and plants.
Open this publication in new window or tab >>Su(z)12, a novel Drosophila Polycomb group gene that is conserved in vertebrates and plants.
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2001 (English)In: Development, ISSN 0950-1991, Vol. 128, no 17, p. 3371-9Article in journal (Other academic) Published
Abstract [en]

In both Drosophila and vertebrates, spatially restricted expression of HOX genes is controlled by the Polycomb group (PcG) repressors. Here we characterize a novel Drosophila PcG gene, Suppressor of zeste 12 (Su(z)12). Su(z)12 mutants exhibit very strong homeotic transformations and Su(z)12 function is required throughout development to maintain the repressed state of HOX genes. Unlike most other PcG mutations, Su(z)12 mutations are strong suppressors of position-effect variegation (PEV), suggesting that Su(z)12 also functions in heterochromatin-mediated repression. Furthermore, Su(z)12 function is required for germ cell development. The Su(z)12 protein is highly conserved in vertebrates and is related to the Arabidopsis proteins EMF2, FIS2 and VRN2. Notably, EMF2 is a repressor of floral homeotic genes. These results suggest that at least some of the regulatory machinery that controls homeotic gene expression is conserved between animals and plants.

Keywords
Amino Acid Sequence, Animals, Arabidopsis/genetics, Conserved Sequence, Drosophila Proteins, Drosophila melanogaster/embryology/*genetics, Female, Gene Expression, Genes; Homeobox, Genes; Insect, Humans, Insect Proteins/*genetics/physiology, Male, Molecular Sequence Data, Mutagenesis, Sequence Homology; Amino Acid, Vertebrates/genetics
Identifiers
urn:nbn:se:umu:diva-17039 (URN)11546753 (PubMedID)
Available from: 2007-10-26 Created: 2007-10-26 Last updated: 2018-06-09Bibliographically approved
2. A 1 MDa ESC/E(Z) complex from Drosophila that contains Polycomblike and RPD3
Open this publication in new window or tab >>A 1 MDa ESC/E(Z) complex from Drosophila that contains Polycomblike and RPD3
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2003 (English)In: Molecular and Cellular Biology, ISSN 0270-7306, E-ISSN 1098-5549, Vol. 23, no 9, p. 3352-3362Article in journal (Refereed) Published
Abstract [en]

Polycomb group (PcG) proteins are required to maintain stable repression of the homeotic genes and others throughout development. The PcG proteins ESC and E(Z) are present in a prominent 600-kDa complex as well as in a number of higher-molecular-mass complexes. Here we identify and characterize a 1-MDa ESC/E(Z) complex that is distinguished from the 600-kDa complex by the presence of the PcG protein Polycomblike (PCL) and the histone deacetylase RPD3. In addition, the 1-MDa complex shares with the 600-kDa complex the histone binding protein p55 and the PcG protein SU(Z)12. Coimmunoprecipitation assays performed on embryo extracts and gel filtration column fractions indicate that, during embryogenesis E(Z), SU(Z)12, and p55 are present in all ESC complexes, while PCL and RPD3 are associated with ESC, E(Z), SU(Z)12, and p55 only in the 1-MDa complex. Glutathione transferase pulldown assays demonstrate that RPD3 binds directly to PCL via the conserved PHD fingers of PCL and the N terminus of RPD3. PCL and E(Z) colocalize virtually completely on polytene chromosomes and are associated with a subset of RPD3 sites. As previously shown for E(Z) and RPD3, PCL and SU(Z)12 are also recruited to the insertion site of a minimal Ubx Polycomb response element transgene in vivo. Consistent with these biochemical and cytological results, Rpd3 mutations enhance the phenotypes of Pcl mutants, further indicating that RPD3 is required for PcG silencing and possibly for PCL function. These results suggest that there may be multiple ESC/E(Z) complexes with distinct functions in vivo.

Place, publisher, year, edition, pages
American Society for microbiology, 2003
National Category
Cell and Molecular Biology Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-5674 (URN)10.1128/MCB.23.9.3352-3362.2003 (DOI)000182325500028 ()12697833 (PubMedID)
Available from: 2003-09-10 Created: 2003-09-10 Last updated: 2018-12-05Bibliographically approved
3. Suppressor of zeste12 mediates silencing through PREs, interacts genetically with other PcG genes and and has a unique binding pattern on polytene chromosomes.
Open this publication in new window or tab >>Suppressor of zeste12 mediates silencing through PREs, interacts genetically with other PcG genes and and has a unique binding pattern on polytene chromosomes.
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-5675 (URN)
Available from: 2003-09-10 Created: 2003-09-10 Last updated: 2019-01-24Bibliographically approved
4. Expression pattern of the Drosophila polycomb group gene Suppressor of zeste 12
Open this publication in new window or tab >>Expression pattern of the Drosophila polycomb group gene Suppressor of zeste 12
(English)Manuscript (Other academic)
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-5676 (URN)
Available from: 2003-09-10 Created: 2003-09-10 Last updated: 2019-01-22Bibliographically approved

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