Project description:Nuclear pore complexes (NPCs) mediate transport across the nuclear envelope. In yeast, they have also been proposed to interact with active genes, attracting or retaining them at the nuclear periphery. However, some NPC components (nucleoporins) in higher eukaryotes are also found in the nucleoplasm, with so far unknown function. Therefore, we have functionally distinguished between nucleoporin-chromatin interactions at the NPC and within the nucleoplasm in Drosophila. For this we analyzed genomic interactions of full-length nucleoporins Nup98, Nup50 and Nup62 and nucleoplasmic and NPC-tethered forms of Nup98. We found that nucleoporins predominantly interacted with transcriptionally active genes inside the nucleoplasm. A smaller set of non-active genes interacted with the NPC. We identified a direct role for nucleoplasmic Nup98 in stimulating gene expression, as genes downregulated upon Nup98 depletion were activated upon nucleoplasmic Nup98 overexpression and showed strong nucleoplasmic Nup98 interaction. Thus, nucleoporins stimulate gene expression away from the NPC by interacting with genes inside the nucleoplasm.
Project description:Nucleus is a highly structured organelle and contains many functional compartments. While the structural basis for this complex spatial organization of compartments is unknown, a major component of this organization is likely to be the non-chromatin scaffolding called nuclear matrix (NuMat). Experimental evidence over the past decades indicates that most of the nuclear functions are at least transiently associated with the NuMat although the components of NuMat itself are poorly known. Here, we report NuMat proteome analysis from Drosophila melanogaster embryos and discuss its links with nuclear architecture and functions. In the NuMat proteome, we find structural proteins, chaperones related, DNA/RNA binding, chromatin remodeling and transcription factors. This complexity of NuMat proteome is an indicator of its structural and functional significance. Comparison of the 2D profile of NuMat proteome from different developmental stages of Drosophila embryos shows that less than half of the NuMat proteome is constant and rest of the proteins are stage specific dynamic components. This NuMat dynamics suggests a possible functional link between NuMat and the embryonic development. Finally, we also show that a subset of NuMat proteins remain associated with the mitotic chromosomes implicating their role in mitosis and possibly the epigenetic cellular memory. NuMat proteome analysis provides tools and opens up ways to understand nuclear organization and function.