Biology Reference
In-Depth Information
A
BX-C
(
Drosophila melanogaster
)
Abd-B
abd-A
Ubx
B
max
0
max
0
Abd-B
abd-A
Ubx
50 kb
Fab-7
Viewpoint
C
abd-A
abd-A
a.
Fab-8
b.
Fab-7
d
Abd-B
Activation
d
b
a
c.
Mcp
c
c
b
a
e
e
d.
Bxd
Abd-B
f
Abd-B
f
e.
Bx
Ubx
Ubx
f.
Abx
Figure 4.6 3D organization of the Drosophila BX-C. (A) Schematic representation of
BX-C with genes indicated as arrows and well-characterized PREs as arrowheads. The
thick grey line indicates the approximate extent of the H3K27me3 coated domain.
(B) Unprocessed 4C signal in the inactive part of BX-C, from third-instar larval brain
and anterior discs. The Fab-7 PRE, regulating Abd-B and located between Abd-B and
abd-A, was used as viewpoint (indicated below). For comparison, the distribution of
the H3K27me3 marks in 4- to 12-h-old embryos is depicted below. (C) Schematic 2D
representation of the BX-C 3D organization. On the left is the 3D organization when
all genes are inactive and on the right is the organization when the Abd-B gene is active.
Grey area represents the H3K27me3 marked 3D compartment. Panel (B) 4C data
from
Bantignies et al. (2011)
and ChIP-on-chip data from
Schuettengruber et al. (2009)
.
Panel (C) based on 3C data from
Lanzuolo, Roure, Dekker, Bantignies, and Orlando (2007)
.
physically separated from the surrounding chromatin. Within this 3D com-
partment, the repressive Polycomb machinery is present at elevated amount,
which may strengthen and/or stabilize repression. Physical interactions
within this chromatin compartment are also dependent on the Polycomb
complex, as its depletion strongly reduces the frequency of these interactions
(
Lanzuolo et al., 2007
).
When the
Abd-B
gene is active, BX-C adopts a different 3D organiza-
tion. In S3 cells, the frequency of interactions between the
Fab-7
PRE and
the active
Abd-B
promoter is strongly decreased, when compared to the
