| 1. |
- Bajusz, Csaba, et al.
(author)
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The nuclear activity of the actin-binding Moesin protein is necessary for gene expression in Drosophila
- 2021
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In: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 288:16, s. 4812-4832
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Journal article (peer-reviewed)abstract
- Ezrin-Radixin-Moesin (ERM) proteins play an essential role in the cytoplasm by cross-linking actin filaments with plasma membrane proteins. Research has identified the nuclear localization of ERMs, as well as the involvement of a single Drosophila ERM protein, Moesin, in nuclear mRNA exports. However, the question of how important the nuclear activity of ERM proteins are for the life of an organism has so far not been explored. Here, we present the first attempt to reveal the in vivo relevance of nuclear localization of Moesin in Drosophila. With the help of a nuclear export signal, we decreased the amount of Moesin in the nuclei of the animals. Furthermore, we observed various developmental defects, demonstrating the importance of ERM function in the nucleus for the first time. Transcriptome analysis of the mutant flies revealed that the lack of nuclear Moesin function leads to expression changes in nearly 700 genes, among them heat-shock genes. This result together with additional findings revealed that in Drosophila the expression of protein chaperones requires the nuclear functions of Moesin.
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| 2. |
- Hari-Gupta, Yukti, et al.
(author)
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Myosin VI regulates the spatial organisation of mammalian transcription initiation
- 2022
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13
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Journal article (peer-reviewed)abstract
- During transcription, RNA Polymerase II (RNAPII) is spatially organised within the nucleus into clusters that correlate with transcription activity. While this is a hallmark of genome regulation in mammalian cells, the mechanisms concerning the assembly, organisation and stability remain unknown. Here, we have used combination of single molecule imaging and genomic approaches to explore the role of nuclear myosin VI (MVI) in the nanoscale organisation of RNAPII. We reveal that MVI in the nucleus acts as the molecular anchor that holds RNAPII in high density clusters. Perturbation of MVI leads to the disruption of RNAPII localisation, chromatin organisation and subsequently a decrease in gene expression. Overall, we uncover the fundamental role of MVI in the spatial regulation of gene expression.
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| 3. |
- Mahmood, Syed Raza, et al.
(author)
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β-actin dependent chromatin remodeling mediates compartment level changes in 3D genome architecture
- 2021
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)abstract
- β-actin is a crucial component of several chromatin remodeling complexes that control chromatin structure and accessibility. The mammalian Brahma-associated factor (BAF) is one such complex that plays essential roles in development and differentiation by regulating the chromatin state of critical genes and opposing the repressive activity of polycomb repressive complexes (PRCs). While previous work has shown that β-actin loss can lead to extensive changes in gene expression and heterochromatin organization, it is not known if changes in β-actin levels can directly influence chromatin remodeling activities of BAF and polycomb proteins. Here we conduct a comprehensive genomic analysis of β-actin knockout mouse embryonic fibroblasts (MEFs) using ATAC-Seq, HiC-seq, RNA-Seq and ChIP-Seq of various epigenetic marks. We demonstrate that β-actin levels can induce changes in chromatin structure by affecting the complex interplay between chromatin remodelers such as BAF/BRG1 and EZH2. Our results show that changes in β-actin levels and associated chromatin remodeling activities can not only impact local chromatin accessibility but also induce reversible changes in 3D genome architecture. Our findings reveal that β-actin-dependent chromatin remodeling plays a role in shaping the chromatin landscape and influences the regulation of genes involved in development and differentiation.
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| 4. |
- Record, Julien, et al.
(author)
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Journey to the Center of the Cell : Cytoplasmic and Nuclear Actin in Immune Cell Functions
- 2021
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In: Frontiers in Cell and Developmental Biology. - : Frontiers Media SA. - 2296-634X. ; 9
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Research review (peer-reviewed)abstract
- Actin cytoskeletal dynamics drive cellular shape changes, linking numerous cell functions to physiological and pathological cues. Mutations in actin regulators that are differentially expressed or enriched in immune cells cause severe human diseases known as primary immunodeficiencies underscoring the importance of efficienct actin remodeling in immune cell homeostasis. Here we discuss recent findings on how immune cells sense the mechanical properties of their environement. Moreover, while the organization and biochemical regulation of cytoplasmic actin have been extensively studied, nuclear actin reorganization is a rapidly emerging field that has only begun to be explored in immune cells. Based on the critical and multifaceted contributions of cytoplasmic actin in immune cell functionality, nuclear actin regulation is anticipated to have a large impact on our understanding of immune cell development and functionality.
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| 5. |
- Venit, Tomas, et al.
(author)
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A dynamic actin-dependent nucleoskeleton and cell identity
- 2021
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In: Journal of Biochemistry (Tokyo). - : Oxford University Press (OUP). - 0021-924X .- 1756-2651. ; 169:3, s. 243-257
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Research review (peer-reviewed)abstract
- Actin is an essential regulator of cellular functions. In the eukaryotic cell nucleus, actin regulates chromatin as a bonafide component of chromatin remodelling complexes, it associates with nuclear RNA polymerases to regulate transcription and is involved in co-transcriptional assembly of nascent RNAs into ribonucleoprotein complexes. Actin dynamics are, therefore, emerging as a major regulatory factor affecting diverse cellular processes. Importantly, the involvement of actin dynamics in nuclear functions is redefining the concept of nucleoskeleton from a rigid scaffold to a dynamic entity that is likely linked to the three-dimensional organization of the nuclear genome. In this review, we discuss how nuclear actin, by regulating chromatin structure through phase separation may contribute to the architecture of the nuclear genome during cell differentiation and facilitate the expression of specific gene programs. We focus specifically on mitochondrial genes and how their dysregulation in the absence of actin raises important questions about the role of cytoskeletal proteins in regulating chromatin structure. The discovery of a novel pool of mitochondrial actin that serves as 'mitoskeleton' to facilitate organization of mtDNA supports a general role for actin in genome architecture and a possible function of distinct actin pools in the communication between nucleus and mitochondria.
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| 6. |
- Venit, Tomas, et al.
(author)
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Nuclear actin and myosin in chromatin regulation and maintenance of genome integrity
- 2020. - 1
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In: Actin Cytoskeleton in Cancer Progression and Metastasis - Part A. - Cambridge : Academic Press. - 9780128212813 ; , s. 67-108
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Book chapter (peer-reviewed)abstract
- Cytoskeletal proteins are beginning to be considered as key regulators of nuclear function. Among them, actin and myosin have been implicated in numerous tasks, including chromatin regulation, transcription and assembly of nascent ribonucleoprotein complexes. We also know from work performed by several labs that influx of actin and myosin into the nucleus and out of the nucleus is tightly regulated. In particular, in the case of actin, its nucleocytoplasmic import/export cycle is controlled by the importin/exportin system and it correlates with the transcriptional state of the cell. These basic molecular functions of both actin and myosin seem to impact key cellular functions, including development and differentiation as well as the cellular response to DNA damage by directly affecting transcriptional reprograming. These observations are beginning to suggest that actin and myosin could play an important role in consolidating the organization of the mammalian genome and that loss of actin and myosin likely leads to a general instability of the genome. In this chapter, we provide a general background on evidence that actin and myosin are important in key nuclear functions. Following this, we will focus on evidence supporting of a role in genome organization and finally we will discuss increasingly striking results on the role of actin and myosin in the maintenance of genome integrity.
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| 7. |
- Venit, Tomas, et al.
(author)
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Nuclear myosin 1 activates p21 gene transcription in response to DNA damage through a chromatin-based mechanism
- 2020
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In: Communications biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Nuclear myosin 1 (NM1) has been implicated in key nuclear functions. Together with actin, it has been shown to initiate and regulate transcription, it is part of the chromatin remodeling complex B-WICH, and is responsible for rearrangements of chromosomal territories in response to external stimuli. Here we show that deletion of NM1 in mouse embryonic fibroblasts leads to chromatin and transcription dysregulation affecting the expression of DNA damage and cell cycle genes. NM1 KO cells exhibit increased DNA damage and changes in cell cycle progression, proliferation, and apoptosis, compatible with a phenotype resulting from impaired p53 signaling. We show that upon DNA damage, NM1 forms a complex with p53 and activates the expression of checkpoint regulator p21 (Cdkn1A) by PCAF and Set1 recruitment to its promoter for histone H3 acetylation and methylation. We propose a role for NM1 in the transcriptional response to DNA damage response and maintenance of genome stability. Venit et al. demonstrate a role for Nuclear myosin 1 (NM1) in the DNA Damage Response by affecting the expression of the p53 target, p21, through chromatin remodeling. They used embryonic fibroblasts from mouse model, high content phenotypic profiling and cell assays, RNA-Seq and ChIP-Seq and pull-down assays and show that NM1 is required for the recruitment of PCAF and SET1 to the p21 gene in response to etoposide.
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| 8. |
- Venit, Tomas, et al.
(author)
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Positive regulation of oxidative phosphorylation by nuclear myosin 1 protects cells from metabolic reprogramming and tumorigenesis in mice
- 2023
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In: Nature Communications. - 2041-1723. ; 14
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Journal article (peer-reviewed)abstract
- Metabolic reprogramming is one of the hallmarks of tumorigenesis. Here, we show that nuclear myosin 1 (NM1) serves as a key regulator of cellular metabolism. NM1 directly affects mitochondrial oxidative phosphorylation (OXPHOS) by regulating mitochondrial transcription factors TFAM and PGC1α, and its deletion leads to underdeveloped mitochondria inner cristae and mitochondrial redistribution within the cell. These changes are associated with reduced OXPHOS gene expression, decreased mitochondrial DNA copy number, and deregulated mitochondrial dynamics, which lead to metabolic reprogramming of NM1 KO cells from OXPHOS to aerobic glycolysis.This, in turn, is associated with a metabolomic profile typical for cancer cells, namely increased amino acid-, fatty acid-, and sugar metabolism, and increased glucose uptake, lactate production, and intracellular acidity. NM1 KO cells form solid tumors in a mouse model, suggesting that the metabolic switch towards aerobic glycolysis provides a sufficient carcinogenic signal. We suggest that NM1 plays a role as a tumor suppressor and that NM1 depletion may contribute to the Warburg effect at the onset of tumorigenesis.
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| 9. |
- Venit, Tomas, et al.
(author)
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Transcriptional Profiling Reveals Ribosome Biogenesis, Microtubule Dynamics and Expression of Specific lncRNAs to be Part of a Common Response to Cell-Penetrating Peptides
- 2020
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In: Biomolecules. - : MDPI AG. - 2218-273X. ; 10:11
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Journal article (peer-reviewed)abstract
- Cell-penetrating peptides (CPPs) are short peptides that are able to efficiently penetrate cellular lipid bilayers. Although CPPs have been used as carriers in conjugation with certain cargos to target specific genes and pathways, how rationally designed CPPs per se affect global gene expression has not been investigated. Therefore, following time course treatments with 4 CPPs-penetratin, PepFect14, mtCPP1 and TP10, HeLa cells were transcriptionally profiled by RNA sequencing. Results from these analyses showed a time-dependent response to different CPPs, with specific sets of genes related to ribosome biogenesis, microtubule dynamics and long-noncoding RNAs being differentially expressed compared to untreated controls. By using an image-based high content phenotypic profiling platform we confirmed that differential gene expression in CPP-treated HeLa cells strongly correlates with changes in cellular phenotypes such as increased nucleolar size and dispersed microtubules, compatible with altered ribosome biogenesis and cell growth. Altogether these results suggest that cells respond to different cell penetrating peptides by alteration of specific sets of genes, which are possibly part of the common response to such stimulus.
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| 10. |
- Xie, Xin, et al.
(author)
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In Mitochondria beta-Actin Regulates mtDNA Transcription and Is Required for Mitochondrial Quality Control
- 2018
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In: iScience. - : Elsevier BV. - 2589-0042. ; 3, s. 226-237
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Journal article (peer-reviewed)abstract
- In eukaryotic cells, actin regulates both cytoplasmic and nuclear functions. However, whether actin-based structures are present in the mitochondria and are involved in mitochondrial functions has not been investigated. Here, using wild-type beta-actin +/+ and knockout (KO) b-actin -/- mouse embryonic fibroblasts we show evidence for the defect in maintaining mitochondrial membrane potential (MMP) in beta-actin-null cells. MMP defects were associated with impaired mitochondrial DNA (mtDNA) transcription and nuclear oxidative phosphorylation (OXPHOS) gene expression. Using super-resolution microscopy we provided direct evidence on the presence of beta-actin-containing structures inside mitochondria. Large aggregates of TFAM-stained nucleoids were observed in bulb-shaped mitochondria in KO cells, suggesting defects in mitochondrial nucleoid segregation without beta-actin. The observation that mitochondria-targeted beta-actin rescued mtDNA transcription and MMP suggests an indispensable functional role of a mitochondrial beta-actin pool necessary for mitochondrial quality control.
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