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Team Publications
Epigenetic plasticity and polarity of the embryo
Year of publication 2009
Benjamin Klapholz, Bruce H Dietrich, Catherine Schaffner, Fabiana Hérédia, Jean-Pierre Quivy,
Geneviève Almouzni, Nathalie Dostatni (2009 May 1)
CAF-1 is required for efficient replication of euchromatic DNA in Drosophila
larval endocycling cells.
Chromosoma : 235-48 : DOI : 10.1007/s00412-008-0192-2
Summary
The endocycle constitutes an effective strategy for cell growth during development. In
contrast to the mitotic cycle, it consists of multiple S-phases with no intervening mitosis and
lacks a checkpoint ensuring the replication of the entire genome. Here, we report an
essential requirement of chromatin assembly factor-1 (CAF-1) for Drosophila larval
endocycles. This complex promotes histone H3-H4 deposition onto newly synthesised DNA in
vitro. In metazoans, the depletion of its large subunit leads to the rapid accumulation of cells
in S-phase. However, whether this slower S-phase progression results from the activation of
cell cycle checkpoints or whether it reflects a more direct requirement of CAF-1 for efficient
replication in vivo is still debated. Here, we show that, strikingly, Drosophila larval
endocycling cells depleted for the CAF-1 large subunit exhibit normal dynamics of
progression through endocycles, although accumulating defects, such as perturbation of
nucleosomal organisation, reduction of the replication efficiency of euchromatic DNA and
accumulation of DNA damage. Given that the endocycle lacks a checkpoint ensuring the
replication of the entire genome, the biological context of Drosophila larval development
offered a unique opportunity to highlight the requirement of CAF-1 for chromatin
organisation and efficient replication processes in vivo, independently of checkpoint
activation.
Year of publication 2008
Katerina R Katsani, Roger E Karess, Nathalie Dostatni, Valérie Doye (2008 Jun 20)
In vivo dynamics of Drosophila nuclear envelope components.
Molecular biology of the cell : 3652-66 : DOI : 10.1091/mbc.E07-11-1162
Summary
Nuclear pore complexes (NPCs) are multisubunit protein entities embedded into the nuclear
envelope (NE). Here, we examine the in vivo dynamics of the essential Drosophila
nucleoporin Nup107 and several other NE-associated proteins during NE and NPCs
disassembly and reassembly that take place within each mitosis. During both the rapid
mitosis of syncytial embryos and the more conventional mitosis of larval neuroblasts,
Nup107 is gradually released from the NE, but it remains partially confined to the nuclear
(spindle) region up to late prometaphase, in contrast to nucleoporins detected by wheat
germ agglutinin and lamins. We provide evidence that in all Drosophila cells, a structure
derived from the NE persists throughout metaphase and early anaphase. Finally, we
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 1
Team Publications
Epigenetic plasticity and polarity of the embryo
examined the dynamics of the spindle checkpoint proteins Mad2 and Mad1. During mitotic
exit, Mad2 and Mad1 are actively imported back from the cytoplasm into the nucleus after
the NE and NPCs have reformed, but they reassociate with the NE only later in G1,
concomitantly with the recruitment of the basket nucleoporin Mtor (the Drosophila
orthologue of vertebrate Tpr). Surprisingly, Drosophila Nup107 shows no evidence of
localization to kinetochores, despite the demonstrated importance of this association in
mammalian cells.
Year of publication 2005
Olivier Crauk, Nathalie Dostatni (2005 Nov 8)
Bicoid determines sharp and precise target gene expression in the Drosophila
embryo.
Current biology : CB : 1888-98
Summary
The activity of the Bicoid (Bcd) transcription factor is a useful example of how quantitative
information contained in a smooth morphogen gradient is transformed into discrete and
precise patterns of target gene expression. There are two distinct and important aspects to
this process: the “sharpening” of the posterior borders of the expression domains and the
“precision” of where the target genes are expressed along the length of the embryo as the
syncytial embryo begins to cellularize. Although the sharpening phenomenon was observed
over a decade ago, it is still poorly understood.
Year of publication 2001
F Janody, R Sturny, V Schaeffer, Y Azou, N Dostatni (2001 Aug 9)
Two distinct domains of Bicoid mediate its transcriptional downregulation by
the Torso pathway.
Development (Cambridge, England) : 2281-90
Summary
The transcriptional activity of the Bicoid morphogen is directly downregulated by the Torso
signal transduction cascade at the anterior pole of the Drosophila embryo. This regulation
does not involve the homeodomain or direct phosphorylation of Bicoid. We analyse the
transcriptional regulation of Bicoid in response to the Torso pathway, using Bicoid variants
and fusion proteins between the Bicoid domains and the Gal4 DNA-binding domain. We show
that Bicoid possesses three autonomous activation domains. Two of these domains, the
serine/threonine-rich and the acidic domains, are downregulated by Torso, whereas the third
activation domain, which is rich in glutamine, is not. The alanine-rich domain, previously
described as an activation domain in vitro, has a repressive activity that is independent of
Torso. Thus, Bicoid downregulation by Torso results from a competition between the
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 2
Team Publications
Epigenetic plasticity and polarity of the embryo
glutamine-rich domain that is insensitive to Torso and the serine/threonine-rich and acidic
activation domains downregulated by Torso. The alanine-rich domain contributes to this
process indirectly by reducing the global activity of the protein and in particular the activity
of the glutamine-rich domain that might otherwise prevent downregulation by Torso.
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 3