Ten different Polycomb group genes are required for spatial control of the abdA and AbdB homeotic products

Mutations in genes of the Polycomb (Pc) group cause abnormal segmental development due to ectopic expression of the homeotic products of the Antennapedia and bithorax complexes. Here the requirements for Pc group genes in controlling the abdA and AbdB products of the bithorax complex are described. Embryos containing mutations in the genes Polycomb (Pc), extra sex combs (esc), Enhancer of zeste [E(z)], polyhomeotic (ph), Sex comb on midleg (Scm), Polycomb-like (Pcl), Sex comb extra (Sce), Additional sex combs (Asx), Posterior sex combs (Psc) and pleiohomeotic (pho) were examined. In every case, both abdA and AbdB are expressed outside of their normal domains along the anterior-posterior (A-P) axis, consistent with these Pc group products acting in a single pathway or molecular complex. The earliest detectable ectopic expression is highest in the parasegments immediately adjacent to the normal expression boundary. Surprisingly, in the most severe Pc group mutants, the earliest ectopic AbdB is distributed in a pair-rule pattern. At all stages, ectopic abdA in the epidermis is highest along the anterior edges of the parasegments, in a pattern that mimics the normal abdA cell-specific pattern. These examples of highly patterned mis-expression show that Pc group mutations do not cause indiscriminate activation of homeotic products. We suggest that the ectopic expression patterns result from factors that normally activate abdA and AbdB only in certain parasegments, but that in Pc group mutants these factors gain access to regulatory DNA in all parasegments.

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Maintenance of the engrailed expression pattern by Polycomb group genes in Drosophila

Development ◽

10.1242/dev.116.3.805 ◽

1992 ◽

Vol 116 (3) ◽

pp. 805-810 ◽

Cited By ~ 7

Author(s):

D. Moazed ◽

P.H. O'Farrell

Keyword(s):

Expression Pattern ◽

Expression Patterns ◽

Ectopic Expression ◽

Polycomb Group ◽

Homeotic Genes ◽

Polycomb Group Genes ◽

Sex Combs ◽

Segment Polarity ◽

Selector Genes ◽

Stable Maintenance

The stable maintenance of expression patterns of homeotic genes depends on the function of a number of negative trans-regulators, termed the Polycomb (Pc) group of genes. We have examined the pattern of expression of the Drosophila segment polarity gene, engrailed (en), in embryos mutant for several different members of the Pc group. Here we report that embryos mutant for two or more Pc group genes show strong ectopic en expression, while only weak derepression of en occurs in embryos mutant for a single Pc group gene. This derepression is independent of two known activators of en expression: en itself and wingless. Additionally, in contrast to the strong ectopic expression of homeotic genes observed in extra sex combs- (esc-) mutant embryos, the en expression pattern is nearly normal in esc- embryos. This suggests that the esc gene product functions in a pathway independent of the other genes in the group. The data indicate that the same group of genes is required for stable restriction of en expression to a striped pattern and for the restriction of expression of homeotic genes along the anterior-posterior axis, and support a global role for the Pc group genes in stable repression of activity of developmental selector genes.

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Needs and Targets for the multi sex combs Gene Product in Drosophila melanogaster

Genetics ◽

10.1093/genetics/149.4.1823 ◽

1998 ◽

Vol 149 (4) ◽

pp. 1823-1838 ◽

Cited By ~ 1

Author(s):

Olivier Saget ◽

Françoise Forquignon ◽

Pedro Santamaria ◽

Neel B Randsholt

Keyword(s):

Drosophila Melanogaster ◽

Ectopic Expression ◽

Polycomb Group ◽

Homeotic Genes ◽

Maternal Control ◽

Gap Gene ◽

Sex Combs ◽

Normal Expression ◽

Selector Genes ◽

Mutant Phenotypes

Abstract We have analyzed the requirements for the multi sex combs (mxc) gene during development to gain further insight into the mechanisms and developmental processes that depend on the important trans-regulators forming the Polycomb group (PcG) in Drosophila melanogaster. mxc is allelic with the tumor suppressor locus lethal (1) malignant blood neoplasm (l(1)mbn). We show that the mxc product is dramatically needed in most tissues because its loss leads to cell death after a few divisions. mxc has also a strong maternal effect. We find that hypomorphic mxc mutations enhance other PcG gene mutant phenotypes and cause ectopic expression of homeotic genes, confirming that PcG products are cooperatively involved in repression of selector genes outside their normal expression domains. We also demonstrate that the mxc product is needed for imaginal head specification, through regulation of the ANT-C gene Deformed. Our analysis reveals that mxc is involved in the maternal control of early zygotic gap gene expression previously reported for some PcG genes and suggests that the mechanism of this early PcG function could be different from the PcG-mediated regulation of homeotic selector genes later in development. We discuss these data in view of the numerous functions of PcG genes during development.

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DSP1, an HMG-like Protein, Is Involved in the Regulation of Homeotic Genes

Genetics ◽

10.1093/genetics/157.1.237 ◽

2001 ◽

Vol 157 (1) ◽

pp. 237-244

Author(s):

M Decoville ◽

E Giacomello ◽

M Leng ◽

D Locker

Keyword(s):

Null Allele ◽

Genetic Interaction ◽

Polycomb Group ◽

Homeotic Genes ◽

Loss Of Function ◽

Sex Combs Reduced ◽

Trithorax Group ◽

Sex Combs ◽

Normal Expression ◽

Sex Comb

Abstract The Drosophila dsp1 gene, which encodes an HMG-like protein, was originally identified in a screen for corepressors of Dorsal. Here we report that loss of dsp1 function causes homeotic transformations resembling those associated with loss of function in the homeotic genes Sex combs reduced (Scr), Ultrabithorax (Ubx), and Abdominal-B. The expression pattern of Scr is altered in dsp1 mutant imaginal discs, indicating that dsp1 is required for normal expression of this gene. Genetic interaction studies reveal that a null allele of dsp1 enhances trithorax-group gene (trx-G) mutations and partially suppresses Polycomb-group gene (Pc-G) mutations. On the contrary, overexpression of dsp1 induces an enhancement of the transformation of wings into halteres and of the extra sex comb phenotype of Pc. In addition, dsp1 male mutants exhibit a mild transformation of A4 into A5. Comparison of the chromatin structure at the Mcp locus in wild-type and dsp1 mutant embryos reveals that the 300-bp DNase I hypersensitive region is absent in a dsp1 mutant context. We propose that DSP1 protein is a chromatin remodeling factor, acting as a trx-G or a Pc-G protein depending on the considered function.

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A role for mel-18, a Polycomb group-related vertebrate gene, during theanteroposterior specification of the axial skeleton

Development ◽

10.1242/dev.122.5.1513 ◽

1996 ◽

Vol 122 (5) ◽

pp. 1513-1522 ◽

Cited By ~ 9

Author(s):

T. Akasaka ◽

M. Kanno ◽

R. Balling ◽

M.A. Mieza ◽

M. Taniguchi ◽

...

Keyword(s):

Dna Sequences ◽

Transcriptional Repression ◽

Ectopic Expression ◽

Axial Skeleton ◽

Polycomb Group ◽

Paraxial Mesoderm ◽

Gene Products ◽

Polycomb Group Genes ◽

Sex Combs ◽

Polycomb Group Gene

Segment identity in both invertebrates and vertebrates is conferred by spatially restricted distribution of homeotic gene products. In Drosophila, the expression of Homeobox genes during embryogenesis is initially induced by segmentation gene products and then maintained by Polycomb group and Trithorax group gene products. Polycomb group gene homologs are conserved in vertebrates. Murine mel-18 and closely related bmi-1 are homologous to posterior sex combs and suppressor two of zeste. Mel-18 protein mediates a transcriptional repression via direct binding to specific DNA sequences. To gain further insight into the function of Mel-18, we have inactivated the mel-18 locus by homologous recombination. Mice lacking mel-18 survive to birth and die around 4 weeks after birth after exhibiting strong growth retardation. Similar to the Drosophila posterior sex combs mutant, posterior transformations of the axial skeleton were reproducibly observed in mel-18 mutants. The homeotic transformations were correlated with ectopic expression of Homeobox cluster genes along the anteroposterior axis in the developing paraxial mesoderm. Surprisingly, mel-18-deficient phenotypes are reminiscent of bmi-1 mutants. These results indicate that the vertebrate Polycomb group genes mel-18 and bmi-1, like Drosophila Polycomb group gene products, might play a crucial role in maintaining the silent state of Homeobox gene expression during paraxial mesoderm development.

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Genetic interactions and dosage effects of Polycomb group genes in mice

Development ◽

10.1242/dev.125.18.3543 ◽

1998 ◽

Vol 125 (18) ◽

pp. 3543-3551 ◽

Cited By ~ 5

Author(s):

S. Bel ◽

N. Core ◽

M. Djabali ◽

K. Kieboom ◽

N. Van der Lugt ◽

...

Keyword(s):

Hox Genes ◽

Expression Patterns ◽

Axial Skeleton ◽

Polycomb Group ◽

Genetic Interactions ◽

Homeotic Gene ◽

Polycomb Group Genes ◽

Dosage Effects ◽

Somitic Mesoderm ◽

Homeotic Gene Expression

In Drosophila and mouse, Polycomb group genes are involved in the maintenance of homeotic gene expression patterns throughout development. Here we report the skeletal phenotypes of compound mutants for two Polycomb group genes bmi1 and M33. We show that mice deficient for both bmi1 and M33 present stronger homeotic transformations of the axial skeleton as compared to each single Polycomb group mutant, indicating strong dosage interactions between those two genes. These skeletal transformations are accompanied with an enhanced shift of the anterior limit of expression of several Hox genes in the somitic mesoderm. Our results demonstrate that in mice the Polycomb group genes act in synergy to control the nested expression pattern of some Hox genes in somitic mesodermal tissues during development.

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A Drosophila ESC-E(Z) Protein Complex Is Distinct from Other Polycomb Group Complexes and Contains Covalently Modified ESC

Molecular and Cellular Biology ◽

10.1128/mcb.20.9.3069-3078.2000 ◽

2000 ◽

Vol 20 (9) ◽

pp. 3069-3078 ◽

Cited By ~ 103

Author(s):

Joyce Ng ◽

Craig M. Hart ◽

Kelly Morgan ◽

Jeffrey A. Simon

Keyword(s):

Germ Line ◽

Gel Filtration ◽

Developmental Time ◽

Polycomb Group ◽

Sex Combs ◽

Sex Comb ◽

Z Protein ◽

Polycomb Group Complexes

ABSTRACT The extra sex combs (ESC) and Enhancer of zeste [E(Z)] proteins, members of the Polycomb group (PcG) of transcriptional repressors, interact directly and are coassociated in fly embryos. We report that these two proteins are components of a 600-kDa complex in embryos. Using gel filtration and affinity chromatography, we show that this complex is biochemically distinct from previously described complexes containing the PcG proteins Polyhomeotic, Polycomb, and Sex comb on midleg. In addition, we present evidence that ESC is phosphorylated in vivo and that this modified ESC is preferentially associated in the complex with E(Z). Modified ESC accumulates between 2 and 6 h of embryogenesis, which is the developmental time whenesc function is first required. We find that mutations inE(z) reduce the ratio of modified to unmodified ESC in vivo. We have also generated germ line transformants that express ESC proteins bearing site-directed mutations that disrupt ESC-E(Z) binding in vitro. These mutant ESC proteins fail to provideesc function, show reduced levels of modification in vivo, and are still assembled into complexes. Taken together, these results suggest that ESC phosphorylation normally occurs after assembly into ESC-E(Z) complexes and that it contributes to the function or regulation of these complexes. We discuss how biochemically separable ESC-E(Z) and PC-PH complexes might work together to provide PcG repression.

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Characterization of Interactions between the Mammalian Polycomb-Group Proteins Enx1/EZH2 and EED Suggests the Existence of Different Mammalian Polycomb-Group Protein Complexes

Molecular and Cellular Biology ◽

10.1128/mcb.18.6.3586 ◽

1998 ◽

Vol 18 (6) ◽

pp. 3586-3595 ◽

Cited By ~ 159

Author(s):

Richard G. A. B. Sewalt ◽

Johan van der Vlag ◽

Marco J. Gunster ◽

Karien M. Hamer ◽

Jan L. den Blaauwen ◽

...

Keyword(s):

Gene Expression ◽

Protein Complexes ◽

Expression Patterns ◽

Polycomb Group ◽

Polycomb Group Protein ◽

Sex Combs ◽

Group Protein ◽

Nuclear Domains ◽

Z Protein

ABSTRACT In Drosophila melanogaster, thePolycomb-group (PcG) andtrithorax-group (trxG) genes have been identified as repressors and activators, respectively, of gene expression. Both groups of genes are required for the stable transmission of gene expression patterns to progeny cells throughout development. Several lines of evidence suggest a functional interaction between the PcG and trxG proteins. For example, genetic evidence indicates that the enhancer of zeste [E(z)] gene can be considered both a PcG and a trxGgene. To better understand the molecular interactions in which the E(z) protein is involved, we performed a two-hybrid screen with Enx1/EZH2, a mammalian homolog of E(z), as the target. We report the identification of the human EED protein, which interacts with Enx1/EZH2. EED is the human homolog ofeed, a murine PcG gene which has extensive homology with the Drosophila PcG gene extra sex combs(esc). Enx1/EZH2 and EED coimmunoprecipitate, indicating that they also interact in vivo. However, Enx1/EZH2 and EED do not coimmunoprecipitate with other human PcG proteins, such as HPC2 and BMI1. Furthermore, unlike HPC2 and BMI1, which colocalize in nuclear domains of U-2 OS osteosarcoma cells, Enx1/EZH2 and EED do not colocalize with HPC2 or BMI1. Our findings indicate that Enx1/EZH2 and EED are members of a class of PcG proteins that is distinct from previously described human PcG proteins.

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Genetic analysis of the enhancer of zeste locus and its role in gene regulation in Drosophila melanogaster.

Genetics ◽

10.1093/genetics/126.1.185 ◽

1990 ◽

Vol 126 (1) ◽

pp. 185-199 ◽

Cited By ~ 9

Author(s):

R S Jones ◽

W M Gelbart

Keyword(s):

Gene Regulation ◽

Drosophila Melanogaster ◽

Ectopic Expression ◽

Polycomb Group ◽

Temperature Sensitive ◽

Loss Of Function ◽

Eye Color ◽

Polycomb Group Genes ◽

Enhancer Of Zeste ◽

Gene Complexes

Abstract The Enhancer of zeste [E(z)] locus of Drosophila melanogaster is implicated in multiple examples of gene regulation during development. First identified as dominant gain-of-function modifiers of the zeste1-white (z-w) interaction, mutant E(z) alleles also produce homeotic transformations. Reduction of E(z)+ activity leads to both suppression of the z-w interaction and ectopic expression of segment identity genes of the Antennapedia and bithorax gene complexes. This latter effect defines E(z) as a member of the Polycomb-group of genes. Analysis of E(z)S2, a temperature-sensitive E(z) allele, reveals that both maternally and zygotically produced E(z)+ activity is required to correctly regulate the segment identity genes during embryonic and imaginal development. As has been shown for other Polycomb-group genes, E(z)+ is required not to initiate the pattern of these genes, but rather to maintain their repressed state. We propose that the E(z) loss-of-function eye color and homeotic phenotypes may both be due to gene derepression, and that the E(z)+ product may be a general repressing factor required for both examples of negative gene regulation.

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Alternative ESC and ESC-Like Subunits of a Polycomb Group Histone Methyltransferase Complex Are Differentially Deployed during Drosophila Development

Molecular and Cellular Biology ◽

10.1128/mcb.26.7.2637-2647.2006 ◽

2006 ◽

Vol 26 (7) ◽

pp. 2637-2647 ◽

Cited By ~ 26

Author(s):

Liangjun Wang ◽

Neal Jahren ◽

Marcus L. Vargas ◽

Erica F. Andersen ◽

Judith Benes ◽

...

Keyword(s):

Histone Methyltransferase ◽

Wing Disc ◽

Polycomb Group ◽

Activity Levels ◽

Loss Of Function ◽

Western Blots ◽

Sex Combs ◽

Wing Discs ◽

Peak Abundance ◽

Regulatory Dna

ABSTRACT The Extra sex combs (ESC) protein is a Polycomb group (PcG) repressor that is a key noncatalytic subunit in the ESC-Enhancer of zeste [E(Z)] histone methyltransferase complex. Survival of esc homozygotes to adulthood based solely on maternal product and peak ESC expression during embryonic stages indicate that ESC is most critical during early development. In contrast, two other PcG repressors in the same complex, E(Z) and Suppressor of zeste-12 [SU(Z)12], are required throughout development for viability and Hox gene repression. Here we describe a novel fly PcG repressor, called ESC-Like (ESCL), whose biochemical, molecular, and genetic properties can explain the long-standing paradox of ESC dispensability during postembryonic times. Developmental Western blots show that ESCL, which is 60% identical to ESC, is expressed with peak abundance during postembryonic stages. Recombinant complexes containing ESCL in place of ESC can methylate histone H3 with activity levels, and lysine specificity for K27, similar to that of the ESC-containing complex. Coimmunoprecipitations show that ESCL associates with E(Z) in postembryonic cells and chromatin immunoprecipitations show that ESCL tracks closely with E(Z) on Ubx regulatory DNA in wing discs. Furthermore, reduced escl + dosage enhances esc loss-of-function phenotypes and double RNA interference knockdown of ESC/ESCL in wing disc-derived cells causes Ubx derepression. These results suggest that ESCL and ESC have similar functions in E(Z) methyltransferase complexes but are differentially deployed as development proceeds.

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Normal and ectopic domains of the homeotic gene Sex combs reduced of Drosophila

Development ◽

10.1242/dev.117.3.917 ◽

1993 ◽

Vol 117 (3) ◽

pp. 917-923 ◽

Cited By ~ 1

Author(s):

S. Pelaz ◽

N. Urquia ◽

G. Morata

Keyword(s):

Ectopic Expression ◽

Secondary Wave ◽

Homeotic Gene ◽

Bithorax Complex ◽

Germ Band ◽

Sex Combs Reduced ◽

Normal Functions ◽

Sex Combs ◽

Normal Expression ◽

Thoracic And Abdominal

The normal expression of the homeotic gene Sex combs reduced (Scr) is initially restricted to parasegment 2, later extends to 3, and by germ band retraction extends further to part of parasegment 4 (T1p). We find that in the absence of the bithorax complex (BX-C) genes there is Scr expression in the epidermis of the posterior compartments of the thoracic and abdominal parasegments. This ectopic expression appears at the same time as the normal one in T1p and requires the normal functions of the genes Antennapedia (Antp) and engrailed (en). In particular, en appears to play an important role in the activation of Scr because the expansion of en expression in naked mutants produces a corresponding expansion of the ectopic Scr stripes. We also find that in the epidermis Antp can have opposite effects on Scr expression; moderate levels of Antp product enhance Scr expression, whereas high levels suppress it. We propose the existence of a secondary wave of Scr activation, which takes place during germ band retraction, is triggered by en and requires Antp expression. It is repressed by the BX-C genes in the meso-, metathoracic and the abdominal segments.

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