Nuclear Cell Biology - CNRS URA2582  

DONNADIEU Françoise / DOUALOT Harry/ DULIEU Isabelle/ Dr. FEUERBACH Frank / Dr. GALY Vincent

  Annual Report

We are studying nuclear structure / function relationships and are mainly focusing on characterizing the regulatory function and molecular determinants of gene positioning within the nuclear space. We are developing biological and informatic tools allowing the accurate measurement of single and multiple gene loci positions in living yeast cells under inactive and active conditions. We also started to study nuclear architecture-linked gene regulation during differentiation and developmental processes in nematodes.

1. Role of transcription and export machineries in spatial positioning of transcribed genes

In several cellular systems, transcriptional states may be linked to specific sub-nuclear compartments. While, in S. cerevisiae, domains close to the nuclear periphery are implicated in transcriptional silencing, it has been proposed that distinct gene loci move to the nuclear envelope (NE) during gene expression. Genetic and physical links exist between the SAGA transcription initiation complex and the mRNA export machinery at the nuclear pore complex (NPC). We therefore analyzed spatial positioning of the GAL genes that are activated by the SAGA complex in response to nutritional change. We developed in collaboration with the Quantitative Image Analyses laboratory (LAIQ) an application for automatic detection and localization of single fluorescently tagged loci in 3D+time and observed that, upon induction, the GAL locus is confined close to the NE. By simultaneous detection of GAL transcripts we showed that transcription occurs preferentially while genes motility is being confined close to the NE. Finally we demonstrated that peripheral positioning is affected in SAGA, export machinery and NPC mutants.

2. Role of the nucleolus on nuclear organization

In order to analyse how genes that need to be co-regulated for ribosome biogenesis are positioned within the nuclear volume, we - in collaboration with LAIQ - extended the gene localization method by introducing a second nuclear landmark different from the NE. Labelling the nucleolus allowed both to analyse gene position with respect to this major sub-nuclear compartment and to orient the imaged nuclei. Since, gene position information of aligned nuclei can be merged, we have for the first time access to statistical robust high precision localization probability maps.

3. Structural and functional nuclear organization in metazoan

In parallel of our analysis in yeast, we analyzed the structure/function relationships in metazoans using human cells in culture as well as C. elegans and D. melanogaster embryos. We started the analysis of several NE components, including the orthologs of the Mlp proteins in these organisms and are currently analyzing their function in the cell as well as at the organism level.

Keywords: functional organization, nuclear envelope, nuclear pore, genetic/epigenetic regulation, gene loci dynamics, genome stability



Berger AB, Decourty L, Badis G, Nehrbass U, Jacquier A, Gadal O. 2007. Hmo1 is required for TOR-dependent regulation of ribosomal protein gene transcription. Mol Cell Biol. 27:8015.

Zuccolo M, Alves A, Galy V, Bolhy S, Formstecher E, Racine V, Sibarita JB, Fukagawa T, Shiekhattar R, Yen T, Doye V. 2007. The human Nup107-160 nuclear pore subcomplex contributes to proper kinetochore functions. EMBO J. 26:1853.

Cabal G, Enninga J. and Mhlanga M.M. 2007. Single molecule tracking of mRNA and proteins. in 'Imaging Cellular and Molecular Biological Function' pp 235-261. S. Shorte & F. Frischknecht Eds., Springer.

Kwon YJ, Genovesio A, Youl Kim N, Hi Chul Kim, Jung S, David-Watine B, Nehrbass U, Emans N. 2007. High-content classification of nucleocytoplasmic import or export inhibitors. J Biomol Screen. 12:621.

Cabal, G. G., A. Genovesio, S. Rodriguez-Navarro, C. Zimmer, O. Gadal, A. Lesne, H. Buc,F. Feuerbach-Fournier, J. C. Olivo-Marin, E. C. Hurt, and U. Nehrbass. 2006. SAGA interacting factors confine sub-diffusion of transcribed genes to the nuclear envelope. Nature 441:770-3.

Galy, V., P. Askjaer, C. Franz, C. Lopez-Iglesias, and I. W. Mattaj. 2006. MEL-28, a novel nuclear-envelope and kinetochore protein essential for zygotic nuclear-envelope assembly in C. elegans. Curr Biol 16:1748-56.

Munter, S., J. Enninga, R. Vazquez-Martinez, E. Delbarre, B. David-Watine, U. Nehrbass, and S. L. Shorte. 2006. Actin polymerisation at the cytoplasmic face of eukaryotic nuclei. BMC Cell Biol 7:23.

Activity Reports 2007 - Institut Pasteur
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