Project description:This SuperSeries is composed of the following subset Series: GSE10697: Self-Self Hybridisation were used to set confidence 99% intervals GSE10698: The effects of artificial tethering of chromosomes to the nuclear periphery using LacI/lap2b anchorage constructs 1 GSE10699: The effects of artificial tethering of chromosomes to the nuclear periphery using LacI/lap2b anchorage constructs 2 Background: The spatial organisation of the genome in the nucleus has a role in the regulation of gene expression. In mammals, chromosomal regions with low gene-density are located close to the nuclear periphery. Correlations have also been made between the transcriptional state of some genes and their location near the nuclear periphery. However, a crucial issue is whether this level of nuclear organisation directly affects gene function, rather than merely reflecting it. Methodology: To directly investigate whether proximity to the nuclear periphery can influence gene expression in mammalian cells. here we relocate specific human chromosomes to the nuclear periphery by tethering them to a protein of the inner nuclear membrane. Principal findings: We show that this can reversibly suppress the expression of some endogenous human genes located near the tethering sites, and even genes further away. However, the expression of many other genes is not detectably reduced and we show that location at the nuclear periphery is not incompatible with active transcription. The dampening of gene expression around the nuclear periphery is dependent on the activity of histone deacetylases. Significance: Our data show that the radial position within the nucleus can influence the expression of some, but not all, genes. This is compatible with the suggestion that re-localisation of genes to the peripheral zone of the nucleus could be used by metazoans to modulate the expression of selected genes during development and differentiation. Keywords: SuperSeries Refer to individual Series
Project description:Background: The spatial organisation of the genome in the nucleus has a role in the regulation of gene expression. In mammals, chromosomal regions with low gene-density are located close to the nuclear periphery. Correlations have also been made between the transcriptional state of some genes and their location near the nuclear periphery. However, a crucial issue is whether this level of nuclear organisation directly affects gene function, rather than merely reflecting it. Methodology: To directly investigate whether proximity to the nuclear periphery can influence gene expression in mammalian cells. here we relocate specific human chromosomes to the nuclear periphery by tethering them to a protein of the inner nuclear membrane. Principal findings: We show that this can reversibly suppress the expression of some endogenous human genes located near the tethering sites, and even genes further away. However, the expression of many other genes is not detectably reduced and we show that location at the nuclear periphery is not incompatible with active transcription. The dampening of gene expression around the nuclear periphery is dependent on the activity of histone deacetylases. Significance: Our data show that the radial position within the nucleus can influence the expression of some, but not all, genes. This is compatible with the suggestion that re-localisation of genes to the peripheral zone of the nucleus could be used by metazoans to modulate the expression of selected genes during development and differentiation. This SuperSeries is composed of the SubSeries listed below.
Project description:Spatial organization of the mammalian genome influences gene expression and cell identity. While association of genes with the nuclear periphery is commonly linked to transcriptional repression, also active, expressed genes can localize at the nuclear periphery. The transcriptionally active MyoD1 gene, a master regulator of myogenesis, exhibits peripheral localization in proliferating myoblasts, yet the underlying mechanisms remain elusive. Using a newly generated reporter cell line, we demonstrate here that peripheral association of the MyoD1 locus is independent of mechanisms involved in heterochromatin anchoring. We identify a set of nuclear envelope transmembrane proteins, particularly WFS1, that actively tether MyoD1 to the nuclear periphery. WFS1 primarily associates with active distal enhancer elements upstream of MyoD1, and with a subset of enhancers enriched in active histone marks genome-wide, which are linked to expressed myogenic genes. Overall, our data identify a novel mechanism involved in tethering active genes to the nuclear periphery. This research was funded in whole or in part by the Austrian Science Fund (FWF) [P29713-B28, P32512-B and P36503-B] to Roland Foisner and a doctorate program funded by the Austrian Science Fund (FWF) [W1261-B28].
Project description:Nuclear compartmentalization appears to play an important role in regulating metazoan genes. While studies on immunoglobulin (Ig) and other loci have correlated positioning at the nuclear lamina with gene repression, the functional consequences of this compartmentalization remain untested. We devised an approach for inducible tethering of genes to the inner nuclear membrane (INM) and demonstrate with 3D DNA-ImmunoFISH, repositioning of chromosomal regions to the nuclear lamina. Relocalization requires mitotic nuclear envelope breakdown and reformation. Tethering leads to the accumulation of lamin and INM proteins but not to association with pericentromeric heterochromatin or nuclear pore complexes. Recruitment of genes to the INM can result in their transcriptional repression. Using DamID we show that as is the case for our model system, inactive Ig loci at the nuclear periphery are contacted by INM and lamina components. We propose that such molecular interactions are used to compartmentalize and limit the accessibility of Ig loci. Experiment Overall Design: We used microarray to analyze the transcription status of genomic regions are inducibly tethered to the INM
Project description:The nuclear lamina is a proteinaceous network of filaments that provide both structural and gene regulatory functions by tethering proteins and large domains of DNA, so-called lamin associated domains (LADs), to the periphery of the nucleus. LADs are a large fraction of the mammalian genome that are repressed, in part, by their association to the nuclear periphery. The genesis and maintenance of LADs is poorly understood as are the proteins that participate in these functions. In an effort to identify proteins that reside at the nuclear periphery and potentially interact with LADs, we have taken a two-pronged approach. First, we have undertaken an interactome analysis of the inner nuclear membrane bound LAP2β to further characterize the nuclear lamina proteome. To accomplish this, we have leveraged the BioID system, which previously has been successfully used to characterize the nuclear lamina proteome. Second, we have established a system to identify proteins that bind to LADs by developing a chromatin directed BioID system. We combined the BioID system with the m6A-tracer system which binds to LADs in live cells to identify LAD proximal and nuclear lamina proteins. In combining these datasets, we have further characterized the protein network at the nuclear lamina as well as identified putative LAD proximal proteins. Our analysis identifies many heterochromatin related proteins related to H3K9 methylation processes as well as many proteins related to cell cycle regulation identifying important proteins essential for LAD function.
Project description:Nuclear compartmentalization appears to play an important role in regulating metazoan genes. While studies on immunoglobulin (Ig) and other loci have correlated positioning at the nuclear lamina with gene repression, the functional consequences of this compartmentalization remain untested. We devised an approach for inducible tethering of genes to the inner nuclear membrane (INM) and demonstrate with 3D DNA-ImmunoFISH, repositioning of chromosomal regions to the nuclear lamina. Relocalization requires mitotic nuclear envelope breakdown and reformation. Tethering leads to the accumulation of lamin and INM proteins but not to association with pericentromeric heterochromatin or nuclear pore complexes. Recruitment of genes to the INM can result in their transcriptional repression. Using DamID we show that as is the case for our model system, inactive Ig loci at the nuclear periphery are contacted by INM and lamina components. We propose that such molecular interactions are used to compartmentalize and limit the accessibility of Ig loci. Keywords: Inducible
Project description:Transcriptionally silent heterochromatin preferentially localizes at the nuclear periphery, but, despite this, certain budding yeast genes relocate to the nuclear periphery following gene activation, implicating the nuclear envelope in both transcriptional activation and silencing. It is unclear how these distinct chromatin domains are established, maintained and distinguished from one another at the nuclear envelope. Here we report that nuclear pore complexes (NPCs) facilitate the transition between chromatin states by providing a platform to which chromatin-remodeling and chromatin-modifying complexes bind. In particular, we show that the RSC chromatin-remodeling complex associates with NPCs and that the nucleoporin Nup170p nucleates heterochromatin formation at telomeres through recruitment of Sir4p. Deletion of NUP170 altered subtelomeric chromatin structure, reduced SIR complex binding at telomeres, impaired telomeric silencing and abated telomere tethering. These results support a model in which telomeric heterochromatin formation occurs through telomere-NPC interactions that both promote Sir4p binding at telomeres and permit chromatin-remodeling complexes to mediate the transition between chromatin states. Examination of genome-wide nucleosome positions in WT and nup170∆ cells via next-generation sequencing of mononucleosomal DNA.
Project description:LMTK3 is an oncogenic receptor tyrosine kinase (RTK) implicated in various types of cancer including breast, lung, gastric and colorectal. It is localized in different cellular compartments but its nuclear function has not been investigated thus far. We have mapped LMTK3 binding across the genome using ChIP-seq and found that LMTK3 binding events are correlated with repressive chromatin markers. We further identified KRAB associated protein-1 (KAP1) as a novel binding partner of LMTK3. The LMTK3/KAP1 interaction is stabilized by PP1_, which suppresses KAP1 phosphorylation specifically at LMTK3-associated chromatin regions, inducing chromatin condensation and resulting in transcriptional repression of LMTK3-bound tumour suppressor-like genes. Furthermore, LMTK3 functions at enhancer regions in tethering the chromatin to the nuclear periphery, resulting in H3K9me3 modification and gene silencing. In summary, we propose a new model where a scaffolding function of nuclear LMTK3 promotes cancer progression through chromatin remodeling, revealing a new mechanism of RTK activity. Examination of LMTK3 binding profile in 2 cell types.