Project description:The cytoplasmic functions of Wiskott-Aldrich Syndrome family (WASP) proteins are well known and include roles in cytoskeleton reorganization and membrane-cytoskeletal interactions important for membrane/vesicle trafficking, morphogenesis, immune response and signal transduction. Mis-regulation of these proteins is associated with immune deficiency and metastasis. Cytoplasmic WASP proteins act as effectors of Rho family GTPases and polymerize branched actin through the Arp2/3 complex. However, recent evidence has revealed that this classically cytoplasmic protein family also functions in the nucleus. Previously, we identified Drosophila washout (wash) as a new member of the WASP family with essential cytoplasmic roles in early development. Here we show that Wash is also present in the nucleus and plays a key role in nuclear organization via its interaction with Lamin Dm0 at the nuclear envelope. Wash and Lamin Dm0 occupy similar genomic regions that overlap with transcriptionally silent chromatin including constitutive heterochromatin. Strikingly, wash mutant and knockdown nuclei exhibit the same abnormal wrinkled morphology observed in diverse laminopathies, including the Hutchinson-Gilford progeria syndrome, and consistent with disruption of the nuclear organization of several sub-nuclear structures including cajal bodies and the chromocenter in salivary glands. We also found that Wash and Lamin knockdown disrupt chromatin accessibility of repressive compartments in agreement with an observed global redistribution of repressive histone modifications. Functional genetic approaches show wash mutants exhibit similar phenotypes to lamin Dm0 mutants, suggesting they participate in similar regulatory networks. Our results reveal a novel role for Wash in modulating nuclear organization via its interaction with the nuclear envelope protein Lamin Dm0. These findings highlight the functional complexity of WASP family proteins and provide new venues to understand their molecular roles in cell biology and disease. We evaluated the effect of Wash knockdown in S2R+ cells on chromatin accessibility using an M.SssI-based approach.
Project description:The cytoplasmic functions of Wiskott-Aldrich Syndrome family (WASP) proteins are well known and include roles in cytoskeleton reorganization and membrane-cytoskeletal interactions important for membrane/vesicle trafficking, morphogenesis, immune response and signal transduction. Mis-regulation of these proteins is associated with immune deficiency and metastasis. Cytoplasmic WASP proteins act as effectors of Rho family GTPases and polymerize branched actin through the Arp2/3 complex. However, recent evidence has revealed that this classically cytoplasmic protein family also functions in the nucleus. Previously, we identified Drosophila washout (wash) as a new member of the WASP family with essential cytoplasmic roles in early development. Here we show that Wash is also present in the nucleus and plays a key role in nuclear organization via its interaction with Lamin Dm0 at the nuclear envelope. Wash and Lamin Dm0 occupy similar genomic regions that overlap with transcriptionally silent chromatin including constitutive heterochromatin. Strikingly, wash mutant and knockdown nuclei exhibit the same abnormal wrinkled morphology observed in diverse laminopathies, including the Hutchinson-Gilford progeria syndrome, and consistent with disruption of the nuclear organization of several sub-nuclear structures including cajal bodies and the chromocenter in salivary glands. We also found that Wash and Lamin knockdown disrupt chromatin accessibility of repressive compartments in agreement with an observed global redistribution of repressive histone modifications. Functional genetic approaches show wash mutants exhibit similar phenotypes to lamin Dm0 mutants, suggesting they participate in similar regulatory networks. Our results reveal a novel role for Wash in modulating nuclear organization via its interaction with the nuclear envelope protein Lamin Dm0. These findings highlight the functional complexity of WASP family proteins and provide new venues to understand their molecular roles in cell biology and disease. DamID chromatin profiling demostrate that Wash binds similar regions to those bound by Lamin Dm0, in particular transcriptional silent chromatin
Project description:Drosophila Haspin kinase phosphorylates Histone H3 at threonine 3 at centromeric heterochromatin and either lamin- or polycomb-enriched euchromatic regions, being required for nuclear organization of interphase cells and polycomb-dependent gene silencing.
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.
Project description:Lamin A/C, a critical nuclear lamina protein, is essential for maintaining nuclear architecture, organizing chromatin and preserving genomic stability. However, its role in directly regulating DNA replication remains unclear. This study investigates how Lamin A/C orchestrates replication initiation by modulating chromatin structure and interacting with proliferating cell nuclear antigen (PCNA). Utilizing high-resolution imaging, chromatin accessibility assays, and sequencing, we demonstrate that Lamin A/C stabilizes replication domains (RDs) by restricting chromatin mobility, preserving spatial organization, and maintaining accessibility. Furthermore, Lamin A/C interacts with PCNA via its Ig-fold domain, regulating PCNA availability by sequestering a pool of PCNA and modulating its expression, and thereby controlling its recruitment to replication machinery. The loss of Lamin A/C results in chromatin architecture reorganization and elevated PCNA availability at RDs, which coordinately trigger excessive activation of replication origins, leading to replication stress and DNA damage. These disruptions prolong the S phase and compromise genome stability, highlighting Lamin A/C as a critical gatekeeper of balanced replication initiation. Our findings reveal Lamin A/C’s dual role in chromatin organization and replication machinery regulation, offering valuable insights into its involvement in replication-associated diseases such as cancer and viral infections and highlighting potential therapeutic opportunities through targeting replication dynamics.
Project description:Lamin A/C, a critical nuclear lamina protein, is essential for maintaining nuclear architecture, organizing chromatin and preserving genomic stability. However, its role in directly regulating DNA replication remains unclear. This study investigates how Lamin A/C orchestrates replication initiation by modulating chromatin structure and interacting with proliferating cell nuclear antigen (PCNA). Utilizing high-resolution imaging, chromatin accessibility assays, and sequencing, we demonstrate that Lamin A/C stabilizes replication domains (RDs) by restricting chromatin mobility, preserving spatial organization, and maintaining accessibility. Furthermore, Lamin A/C interacts with PCNA via its Ig-fold domain, regulating PCNA availability by sequestering a pool of PCNA and modulating its expression, and thereby controlling its recruitment to replication machinery. The loss of Lamin A/C results in chromatin architecture reorganization and elevated PCNA availability at RDs, which coordinately trigger excessive activation of replication origins, leading to replication stress and DNA damage. These disruptions prolong the S phase and compromise genome stability, highlighting Lamin A/C as a critical gatekeeper of balanced replication initiation. Our findings reveal Lamin A/C’s dual role in chromatin organization and replication machinery regulation, offering valuable insights into its involvement in replication-associated diseases such as cancer and viral infections and highlighting potential therapeutic opportunities through targeting replication dynamics.
Project description:Lamin A/C, a critical nuclear lamina protein, is essential for maintaining nuclear architecture, organizing chromatin and preserving genomic stability. However, its role in directly regulating DNA replication remains unclear. This study investigates how Lamin A/C orchestrates replication initiation by modulating chromatin structure and interacting with proliferating cell nuclear antigen (PCNA). Utilizing high-resolution imaging, chromatin accessibility assays, and sequencing, we demonstrate that Lamin A/C stabilizes replication domains (RDs) by restricting chromatin mobility, preserving spatial organization, and maintaining accessibility. Furthermore, Lamin A/C interacts with PCNA via its Ig-fold domain, regulating PCNA availability by sequestering a pool of PCNA and modulating its expression, and thereby controlling its recruitment to replication machinery. The loss of Lamin A/C results in chromatin architecture reorganization and elevated PCNA availability at RDs, which coordinately trigger excessive activation of replication origins, leading to replication stress and DNA damage. These disruptions prolong the S phase and compromise genome stability, highlighting Lamin A/C as a critical gatekeeper of balanced replication initiation. Our findings reveal Lamin A/C’s dual role in chromatin organization and replication machinery regulation, offering valuable insights into its involvement in replication-associated diseases such as cancer and viral infections and highlighting potential therapeutic opportunities through targeting replication dynamics.