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Publications de l’équipe
Compartimentation et dynamique des fonctions nucléaires
Année de publication : 2010
Hani Ebrahimi, E Douglas Robertson, Angela Taddei, Susan M Gasser, Anne D Donaldson, Shinichiro Hiraga (2010 Mar 4)
Early initiation of a replication origin tethered at the nuclear periphery.
Journal of cell science : 1015-9 : DOI : 10.1242/jcs.060392
Résumé
Peripheral nuclear localization of chromosomal loci correlates with late replication in yeast
and metazoan cells. To test whether peripheral positioning can impose late replication, we
examined whether artificial tethering of an early-initiating replication origin to the nuclear
periphery delays its replication in budding yeast. We tested the effects of three different
peripheral tethering constructs on the time of replication of the early replication origin
ARS607. Using the dense-isotope transfer method to assess replication time, we found that
ARS607 still replicates early when tethered to the nuclear periphery using the Yif1 protein or
a fragment of Sir4, whereas tethering using a Yku80 construct produces only a very slight
replication delay. Single-cell microscopic analysis revealed no correlation between peripheral
positioning of ARS607 in individual cells and delayed replication. Overall, our results
demonstrate that a replication origin can initiate replication early in S phase, even if
artificially relocated to the nuclear periphery.
Année de publication : 2009
Angela Taddei, Griet Van Houwe, Shigeki Nagai, Ionas Erb, Erik van Nimwegen, Susan M Gasser
(2009 Jan 31)
The functional importance of telomere clustering: global changes in gene
expression result from SIR factor dispersion.
Genome research : 611-25 : DOI : 10.1101/gr.083881.108
Résumé
Budding yeast telomeres and cryptic mating-type loci are enriched at the nuclear envelope,
forming foci that sequester silent information regulators (SIR factors), much as
heterochromatic chromocenters in higher eukaryotes sequester HP1. Here we examine the
impact of such subcompartments for regulating transcription genome-wide. We show that
the efficiency of subtelomeric reporter gene repression depends not only on the strength of
SIR factor recruitment by cis-acting elements, but also on the accumulation of SIRs in such
perinuclear foci. To monitor the effects of disrupting this subnuclear compartment, we
performed microarray analyses under conditions that eliminate telomere anchoring, while
preserving SIR complex integrity. We found 60 genes reproducibly misregulated. Among
those with increased expression, 22% were within 20 kb of a telomere, confirming that the
nuclear envelope (NE) association of telomeres helps repress natural subtelomeric genes. In
contrast, loci that were down-regulated were distributed over all chromosomes. Half of this
ectopic repression was SIR complex dependent. We conclude that released SIR factors can
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 1
Publications de l’équipe
Compartimentation et dynamique des fonctions nucléaires
promiscuously repress transcription at nontelomeric genes despite the presence of « antisilencing » mechanisms. Bioinformatic analysis revealed that promoters bearing the PAC
(RNA Polymerase A and C promoters) or Abf1 binding consenses are consistently downregulated by mislocalization of SIR factors. Thus, the normal telomeric sequestration of SIRs
both favors subtelomeric repression and prevents promiscuous effects at a distinct subset of
promoters. This demonstrates that patterns of gene expression can be regulated by
changing the spatial distribution of repetitive DNA sequences that bind repressive factors.
Année de publication : 2008
Myriam Ruault, Marion Dubarry, Angela Taddei (2008 Sep 30)
Re-positioning genes to the nuclear envelope in mammalian cells: impact on
transcription.
Trends in genetics : TIG : 574-81 : DOI : 10.1016/j.tig.2008.08.008
Résumé
The spatial organization of the genome within the nucleus is thought to contribute to
genome functions. A key component of the nuclear architecture is the nuclear envelope,
which is often associated with inactive chromatin. Studies in budding yeast indicate that
nuclear position can directly affect gene function. However, the causal relationship between
gene position and gene activity in mammalian cells has been more elusive. Several groups
recently addressed this issue by tethering genes to the inner nuclear membrane. Their
studies show that the nuclear periphery is not refractory to gene transcription, but can
modulate the activity of certain genes. The 3D organization of the genome might, thus,
provide an additional level of regulation necessary for fine-tuning gene expression.
Année de publication : 2007
Angela Taddei (2007 May 1)
Active genes at the nuclear pore complex.
Current opinion in cell biology : 305-10
Résumé
The nucleus is spatially and functionally organized and its architecture is now seen as a key
contributor to genome functions. A central component of this architecture is the nuclear
envelope, which is studded with nuclear pore complexes that serve as gateways for
communication between the nucleoplasm and cytoplasm. Although the nuclear periphery
has traditionally been described as a repressive compartment and repository for gene-poor
chromosome regions, several recent studies in yeast have demonstrated that repressive and
activating domains can both be positioned at the periphery of the nucleus. Moreover,
association with the nuclear envelope favors the expression of particular genes,
demonstrating that nuclear organization can play an active role in gene regulation.
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 2
Publications de l’équipe
Compartimentation et dynamique des fonctions nucléaires
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 3