Transcriptional silencing by the Polycomb Group of genes maintains the position-specific repression of homeotic genes throughout Drosophila development. The Polycomb Group of genes characterized to date encode chromatin-associated proteins that have been suggested to form heterochromatin-like structures. By studying the expression of reporter genes, we have identified a 725 bp fragment, called MCP725, in the homeotic gene Abdominal-B, that accurately maintains position-specific silencing during proliferation of imaginal cells. Silencing by MCP725 requires the Polycomb and the Polycomblike genes, indicating that it contains a Polycomb response element To investigate the mechanisms of transcriptional silencing by MCP725, we have studied its temporal requirements by removing MCP725 from the transgene at various times during development. We have discovered that excision of MCP725 during larval stages leads to loss of silencing. Our findings indicate that the silencer is required for the maintenance of the repressed state throughout cell proliferation. They also suggest that propagation of the silenced state does not occur merely by templating of a heterochromatin structure by virtue of protein-protein interactions. Rather, they suggest that silencers play an active role in the maintenance of the position-specific repression throughout development.
REFERENCES
REFERENCES
Akam
M. E.
(1987
) The molecular basis for metameric pattern in the Drosophila embryo.
Development
101
, 1
–22
Appel
B.
, Sakonju
S.
(1993
) Cell-type-specific mechanisms of transcriptional repression by the homeotic gene products Ubx and abd-A in Drosophila embryos.
EMBO J
12
, 1099
–1109
Bienz
M.
(1992
) Molecular mechanisms of determination in Drosophila.
Curr. Opin. Cell Biol
4
, 955
–961
Bienz
M.
, Muller
J.
(1995
) Transciptional silencing of homeotic genes in Drosophila.
BioEssays
17
, 775
–784
Brand
A. H.
, Breeden
L.
, Abraham
J.
, Sternglanz
R.
, Nasmyth
K.
(1985
) Characterization of a ‘silencer’ in yeast: A DNA sequence with properties opposite to those of a transcriptional enhancer.
Cell
41
, 41
–48
Brown
C.
, Willard
H.
(1994
) The human X-inactivation center is not required for maintenance of X-chromosome inactivation.
Nature
368
, 154
–156
Bunker
C.
, Kingston
R.
(1994
) Transcriptional repression by Drosophila and mammalian Polycomb group proteins in transfected mmammalian cells.
Mol. Cell Biol
14
, 1721
–1723
Busturia
A.
, Bienz
M.
(1993
) Silencers in Abdominal-B, a homeotic Drosophila gene.
EMBO J
12
, 1415
–1425
Casares
F.
, Sánchez-Herrero
E.
(1995
) Regulation of the infraabdominal regions of the bithorax complex of Drosophila by gap genes.
Development
121
, 1855
–1866
Castelli-Gair
J.
, Muller
J.
, Bienz
M.
(1992
) Function of an Ultrabithorax minigene in imaginal cells.
Development
114
, 877
–886
Celniker
S. E.
, Sharma
S.
, Keelan
D. J.
, Lewis
E. B.
(1990
) The molecular genetics of the Bithorax complex of Drosophila: cis-regulation in the Abdominal-B domain.
EMBO J
9
, 4277
–4286
Chan
C.-S.
, Rastelli
L.
, Pirrotta
V.
(1994
) A Polycomb response element in the Ubx gene that determines an epigenetically inherited state of repression.
EMBO J
13
, 2553
–2564
Christen
B.
, Bienz
M.
(1994
) Imaginal disc silencers from Ultrabithorax: evidence for Polycomb response elements.
Mech. Dev
48
, 255
–266
Dernburg.
A.F.
, Broman
K. W.
, Fung
J.C.
, Marshall
W.F.
, Philips
J.
, Agard
D.A.
, Sedat
J.W.
(1996
) Perturbation of nuclear architecture by long-distance chromosome interactions.
Cell
85
, 745
–759
Duncan
I.
(1982
) Polycomblike: A gene that appears to be required for the normal expression of the bithorax and Antennapedia gene complexes of Drosophila melanogaster.
Genetics
102
, 49
–70
Eissenberg
J.C.
, James
T.C.
, Foster-Hartnett
D.M.
, Martnett
T.
, Ngan
V.
, Elgin
S.
(1990
) Mutation in a heterochromatin-specific chromosomal protein is associated with suppression of position effect variegation in Drosophila melanogaster.
Proc. Natl. Acad. Sci.USA
87
, 9923
–9927
Gaul
U.
, Jäckle
H.
(1989
) Analysis of maternal effect mutant combinations elucidates regulation and function of the overlap of hunchback and Kruppel gene expression in the Drosophila blastoderm embryo.
Development
107
, 651
–662
Gehring
W. J.
, Qian
Y. Q.
, Billeter
M.
, Furukubo-Tokunaga
K.
, Schier
A. F.
, Resendez-Perez
D.
, Affolter
M.
, Otting
G.
, Wuthrich
K.
(1994
) Homeodomain-DNA recognition.
Cell
78
, 211
–223
Golic
K.
, Lindquist
S. L.
(1989
) The FLP recombinase of yeast catalyzes site-specific recombination in the Drosophila genome.
Cell
59
, 499
–509
Golic
M. M.
, Golic
K. G.
(1996
) A quantitative measure of the mitotic pairing of alleles in Drosophila melanogaster and the influence of structural heterozygosity.
Genetics
143
, 385
–400
Gould
A.P.
, Lai
R.Y.K.
, Green
M.J.
, White
R.A.H.
(1990
) Blocking cell division does not remove the requirement for Polycomb function in Drosophila embryogenesis.
Development
110
, 1319
–1325
Hama
C.
, Ali
Z.
, Kornberg
T.
(1990
) Region specific recombination and expression are directed by portions of the Drosophila engrailed promoter.
Genes Dev
4
, 1079
–1093
Harding
K.
, Levine
M.
(1988
) Gap genes define the limits of Antennapedia and Bithorax gene expression during early development in Drosophila.
EMBO J
7
, 205
–214
Hargstrom
K.
, Muller
M.
, Schedl
P.
(1996
) Fab-7 functions as a chromatin domain boundary to ensure proper segment specification by the Drosophila bithorax complex.
Genes Dev
10
, 3202
–3215
Holmes
S. G.
, Broach
J. R.
(1996
) Silencers are required for inheritance of the repressed state in yeast.
Genes Dev
10
, 1021
–1032
Jones
R. S.
, Gelbart
W. M.
(1993
) Genetics analysis of the Enhancer of zeste and its role in gene regulation in Drosophila melanogaster.
Genetics
126
, 185
–199
Jurgens
G.
(1985
) A group of genes controlling the spatial expression of the bithorax complex in Drosophila.
Nature
316
, 153
–155
Karch
F.
, Galloni
M.
, Spios
L.
, Gausz
J.
, Gyurkovics
H.
, Schedl
P.
(1994
) Mcp and Fab −7: molecular analyssis of putative boundaries of cis -regulatory domains in the bithorax complex of Drosophila melanogaster.
Nucl. Acids Res
22
, 3138
–3146
Karch
F.
, Weiffenbach
B.
, Peifer
M.
, Bender
W.
, Duncan
I.
, Celniker
S.
, Crosby
M.
, Lewis
E. B.
(1985
) The abdominal region of the Bithorax complex.
Cell
43
, 81
–96
Krasnow
M. A.
, Saffman
E. E.
, Kornfeld
K.
, Hogness
D. S.
(1989
) Transcriptional activation and repression by Ultrabithorax proteins in cultured Drosophila cells.
Cell
57
, 1031
–1043
Laurenson
P.
, Rine
J.
(1992
) Silencers, silencing and heritable transcriptional states.
Microbiol. Rev
56
, 543
–563
Locke
J.
, Kotarski
M.
, Tartof
K.
(1988
) Dosage-dependent modifiers of position effect variegation in Drosophila and a mass action model that explains their effect.
Genetics
120
, 181
–198
Lonie
A.
, D'Andrea
R.
, Paro
R.
, Saint
R.
(1994
) Molecular characterization of the Polycomblike gene of Drosophila melanogaster, a trans-acting negative regulator of homeotic gene expression.
Development
120
, 2629
–2636
Loo
S.
, Rine
J.
(1995
) Silencing and heritable domains of gene expression.
Ann. Rev. Cell Biol
11
, 519
–48
McCall
K.
, Bender
W.
(1996
) Probes for chromatin accessibility in the Drosophila bithorax complex respond differently to Polycomb mediated repression.
EMBO J.,
15
, 569
–580
Moehrle
A.
, Paro
R.
(1994
) Spreading the silence: epigenetic transcriptional regulation during Drosophila development.
Dev. Genet
15
, 478
–484
Muller
J.
, Bienz
M.
(1991
) Long range repression conferring boundaries of Ultrabithorax expression in the Drosophila embryo.
EMBO J
10
, 1415
–1425
Orenic
T.
, Slusarski
D.
, Kroll
K.
, Holmgren
R.
(1990
) Cloning and characterization of the segment polarity gene cubitus interruptus Dominant of Drosophila.
Genes Dev
4
, 1053
–1067
Orlando
V.
, Paro
R.
(1993
) Mapping Polycomb-repressed domains in the bithorax complex using in vivo formaldehyde cross-linked chromatin.
Cell
75
, 1187
–1198
Orlando
V.
, Paro
R.
(1995
) Chromatin multiprotein complexes involved in the maintenance of transcription patterns.
Curr. Opin. Genet. Dev
5
, 174
–179
Paro
R.
, Hogness
D.
(1991
) The Polycomb protein shares a homologous domain with heterochromatin-associated protein in Drosophila.
Proc. Natl. Acad. Sci. USA
88
, 263
–267
Pirrotta
V.
(1997
) PcG complexes and chromatin silencing.
Curr. Opin. Genet. Dev
7
, 249
–258
Pirrotta
V.
, Rastelli
L.
(1994
) white gene expression, repressive chromatin domains and homeotic gene silencing in Drosophila.
BioEssays
16
, 549
–555
Raff
J. W.
, Kellum
R.
, Alberts
B.
(1994
) The Drosophila GAGA transcription factor is associated with specific regions of heterochromatin throughout cell cycle.
EMBO J
13
, 5977
–5983
Sánchez-Herrero
E.
(1991
) Control of the expression of the bithorax complex genes abdominal-A and Abdominal-B by cis -regulatory regions in Drosophila embryos.
Development
111
, 437
–449
Sánchez-Herrero
E.
, Akam
M.
(1989
) Spatially ordered transcription of regulatory DNA in the bithorax complex of Drosophila.
Development
107
, 321
–329
Sánchez-Herrero
E.
, Vernos
I.
, Marco
R.
, Morata
G.
(1985
) Genetic organization of Drosophila bithorax complex.
Nature
313
, 108
–113
Simon
J.
(1995
) Locking in stable states of gene expression: transcriptional control during Drosophila development.
Curr. Opin. Cell Biol
7
, 376
–385
Simon
J.
, Chiang
A.
, Bender
W.
(1992
) Ten different Polycomb group genes are required for spatial control of the abd-A and Abd-B homeotic products.
Development
114
, 493
–505
Simon
J.
, Chiang
A.
, Bender
W.
, Shimell
M. J.
, O'Connor
M.
(1993
) Elements of the Drosophila Bithorax complex that mediate repression by Polycomb group products.
Dev. Biol
158
, 131
–144
Soto
M.
, Chou
T.
, Bender
W.
(1995
) Comparison of germline mosaics of genes in the Polycomb Group of Drosophila melanogaster.
Genetics
140
, 231
–243
Struhl
G.
, Akam
M.
(1985
) Altered distributions of Ultrabithorax transcripts in extra sex combs mutant embryos of Drosophila.
EMBO J
4
, 3259
–3264
Strutt
H.
, Cavalli
G.
, Paro
R.
(1997
) Co-localization of Polycomb protein and GAGA factor on regulatory elements responsible for the maintenance of homeotic gene expression.
EMBO J
16
, 3621
–3623
Tautz
D.
(1988
) Regulation of the Drosophila segmentation gene hunchback by two maternal morphogenetic centres.
Nature
332
, 281
–284
Winslow
G. M.
, Hayashi
S.
, Krasnow
M.
, Hogness
D. S.
, Scott
M. P.
(1989
) Transcriptional activation by the Antennapedia and fushi tarazu proteins in cultured Drosophila cells.
Cell
57
, 1017
–1030
Xu
T.
, Rubin
G.
(1993
) Analysis of genetic mosaics in developing and adult Drosophila tissues.
Development
117
, 1223
–1237
Zavortink
M.
, Sakonju
S.
(1989
) The morphogenetic and regulatory functions of the Drosophila Abdominal-B gene are encoded in overlapping RNAs transcribed from separate promoters.
Genes Dev
3
, 1969
–1981
Zhang
C.
, Bienz
M.
(1992
) Segmental determination in Drosophila conferred by hunchback (hb), a repressor of the homeotic gene Ultrabithorax.
Proc. Natl. Acad. Sci. USA
89
, 7511
–7515
Zhang
C.
, Muller
J.
, Hoch
M.
, Jackle
H.
, Bienz
M.
(1991
) Target sequences for hunchback in a control region conferring Ultabithorax expression boundaries.
Development
113
, 1171
–1179
Zhou
J.
, Barolo
S.
, Szymanski
P.
, Levine
M.
(1996
) The Fab-7 element of the bithorax complex attenuates enhancer-promoter interactions in the Drosophila embryo.
Genes Dev
10
, 3195
–3201
This content is only available via PDF.
© 1997 by Company of Biologists
1997
