Nuclear actin activates human transcription factor genes including the OCT4 gene
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE59799 | GEO | 2014/11/10
SECONDARY ACCESSION(S): PRJNA256267
REPOSITORIES: GEO
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Project description:Oct4 is an essential regulator of embryonic stem (ES) cell pluripotency in vivo and in vitro, as well as a key mediator of the reprogramming of somatic cells to form induced pluriopotent stem (iPS) cells. It is not known whether activation and/or repression of specific genes by Oct4 is relevant to these functions. Here we show that fusion proteins containing the coding sequence of Oct4 or Xlpou91 (the Xenopus homologue of Oct4) fused to activating regions, but not those fused to repressing regions, behave as Oct4, suppressing differentiation and promoting maintenance of undifferentiated phenotypes in vivo and in vitro. An Oct4 activation domain fusion supported ES cell self-renewal in vitro at lower concentrations than required for Oct4 while alleviating the ordinary requirement for the cytokine LIF. At still lower levels of the fusion, LIF-dependence was restored. We conclude that the necessary and sufficient function of Oct4 in promoting pluripotency is to activate specific target genes.
2012-02-27 | GSE24563 | GEO
Project description:The transcription factor Oct4/Pou5f1 is a key component of the regulatory circuitry governing pluripotency. Oct4 is also widely used to generate induced pluripotent stem cells (iPSCs) from somatic cells. These observations provide compelling rationale to understand Oct4’s functions. Here we used domain swapping and mutagenesis to compare Oct4’s reprogramming activity with the paralog Oct1/Pou2f1, identifying a redox-sensitive DNA binding domain cysteine residue (Cys48) as a key determinant of both reprogramming and differentiation. In combination with the Oct4 N-terminus, mutating Oct1’s serine at this position to cysteine is sufficient to confer strong reprogramming activity. Conversely, Oct4C48S strongly reduces reprogramming potential. Oct4C48S renders the protein insensitive to oxidative inhibition of DNA binding. The same mutation prevents oxidation-mediated protein ubiquitylation. An engineered Pou5f1C48S point mutation has little effect on undifferentiated cells embryonic stem cells (ESCs), but upon retinoic acid (RA)-mediated differentiation causes retention of Oct4 expression, decreased proliferation, and increased apoptosis. Transcriptional profiling reveals that the retention of pluripotency also manifests at the RNA level. Pou5f1C48S ESCs also contribute poorly to adult somatic tissues and form less differentiated teratomas. Collectively, the data support a model in which Oct4 redox sensing is a positive reprogramming determinant during one or more reprogramming steps, and mediates Oct4 degradation during differentiation.
2024-04-09 | GSE241332 | GEO
Project description:Replacing the transcription factor OCT4, one of the master pluripotency regulators, by small molecules has been a long standing challenge to establish small molecule based reprogramming for the generation of human chemically induced pluripotent stem cells (hciPSCs). Using a cell-based high throughput screen, we have previously identified a new series of OCT4-inducing compounds (O4Is). In this paper, we prepared metabolically stable analogues, including O4I4, which strongly activate pluripotency-associated signaling. In combination with a transcription factor cocktail of SOX2, KLF4, MYC, and LIN28 (collectively referred to as CSKML) we achieved to reprogram human fibroblasts into a stable and authentic pluripotent state independent of exogenous OCT4. Transcriptomic analysis of fibroblasts reprogrammed by this approach revealed that O4I4 activated bone morphogenetic protein (BMP)/SMAD/ID signaling at the early stage of reprogramming and subsequent expression of the chromatin modifier, high mobility group A1 (HMGA1), resulting in re-activation of endogenous OCT4 to initiate the reprogramming process. Consistently, chemical or genetic inhibition of BMP/SMAD/ID or HMGA1 was found to block cellular reprogramming. In C.elegans and Drosophila, O4I4 expanded life spans in a BMP-signaling pathway-dependent manner. Given limitations of OCT4-based reprogramming, our findings provide an alternative to OSKM-mediated iPSC generation, and importantly unravel previously-unrecognized molecular mechanisms of pluripotency in the context of regenerative medicine and rejuvenation therapy.
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Project description:Actin dynamically shuttles between the nucleus and cytosplasm and regulates a wide range of transcriptional processes within the nucleus We used gene expression profiling of keratinocytes overexpressing wild type actin or actin tagged with a nuclear localisation sequence to identify genes specifically regulated by nuclear actin
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Project description:Nuclear actin has been elusive due to the lack of molecular mechanisms. From actin-containing chromatin remodeling complexes, we discovered an arginine mono-methylation mark on evolutionarily conserved R256 residue of actin (R256me1). Actin R256 mutations in yeast affect nuclear functions, and cause diseases in human. Interestingly, we show that an antibody specific for actin R256me1 preferentially stain nuclear actin over cytoplasmic actin in yeast, mouse and human cells. We also show that actin R256me1 is regulated by protein arginine methyl transferase-5 (PRMT5) in HEK293 cells. Genome-wide survey of actin R256me1 mark provides a landscape for nuclear actin correlated with transcription. Further gene expression and protein interaction studies uncover extensive correlations between actin R256me1 and active transcription. The discovery of actin R256me1 mark suggests a fundamental mechanism to distinguish nuclear actin from cytoplasmic actin through post-translational modification (PTM), and potentially implicates an actin PTM mark in transcription and human diseases.
2020-08-26 | GSE156817 | GEO
Project description:Polymerized b-actin may provide a structural basis for chromatin accessibility. Nuclear actin transport into the nucleus can determine mesenchymal stem cell (MSC) differentiative outcomes through regulated control of gene expression. Using MSC, we show that inhibiting Arp2/3 directed secondary actin branching with CK666, which results in decreased nuclear actin structure, significantly alters chromatin access measured with ATAC-seq at 24 h. The ATAC-seq results due to CK666 are distinct from those caused by cytochalasin D (CytoD), which increases nuclear actin structure. Nuclear visualization shows Arp2/3 inhibition is associated with decreased pericentric H3K9me3 marks. CytoD, in contrast, induces relocation of H3K27me3 marks away from the inner membrane. Treatment induced alterations in the chromatin landscape at 24 hours prompts differential gene expression associated with decreased proliferation and increased differentiation. Further, knockdown of the non-enzymatic monomeric actin binding protein, Arp4, leads to extensive chromatin unpacking, but only a modest change in transcription, indicating an active role for actin-Arp4 in transcription. These data indicate that dynamic actin remodeling can regulate chromatin interactions.
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Project description:The evolutionary origins of the gene network underlying cellular pluripotency, a central theme in developmental biology, have yet to be elucidated. In mammals, Oct4 is a factor crucial in the reprogramming of differentiated cells into induced pluripotent stem cells. The Oct4 and Pou2 genes evolved from a POU class V gene ancestor, but it is unknown whether pluripotency induced by Oct4 gene activity is a feature specific to mammals or was already present in ancestral vertebrates. Here we report that different vertebrate Pou2 and Oct4 homologues can induce pluripotency in mouse and human fibroblasts and that the inability of zebrafish Pou2 to establish pluripotency is not representative of all Pou2 genes, as medaka Pou2 and axolotl Pou2 are able to reprogram somatic cells into pluripotent cells. Therefore, our results indicate that induction of pluripotency is not a feature specific to mammals, but existed in the Oct4/Pou2 common ancestral vertebrate. 16 samples were analyzed Notation: O: stands for OCT4 reprogramming factor from human; o: stands for Oct4 reprogramming factor from Axolotl S: stands for SOX2 reprogramming factor from human; s: stands for SOX2 reprogramming factor from Axolotl K: stands for KLF4 reprogramming factor from human
2014-03-23 | E-GEOD-21302 | biostudies-arrayexpress
Project description:Polymerized B-actin may provide a structural basis for chromatin accessibility and actin transport into the nucleus can guide mesenchymal stem cell (MSC) differentiation. Using MSC, we show that using CK666 to inhibit Arp2/3 directed secondary actin branching results in decreased nuclear actin structure, and significantly alters chromatin access measured with ATACseq at 24 h. The ATAC-seq results due to CK666 are distinct from those caused by cytochalasin D (CytoD), which enhances nuclear actin structure. In addition, nuclear visualization shows Arp2/3 inhibition decreases pericentric H3K9me3 marks. CytoD, alternatively, induces redistribution of H3K27me3 marks centrally. Such alterations in chromatin landscape are consistent with differential gene expression associated with distinctive differentiation patterns. Further, knockdown of the non-enzymatic monomeric actin binding protein, Arp4, leads to extensive chromatin unpacking, but only a modest increase in transcription, indicating an active role for actin-Arp4 in transcription. These data indicate that dynamic actin remodeling can regulate chromatin interactions.
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Project description:Oct4 is widely considered the most important among the four Yamanaka reprogramming factors. Here we show that the combination of Sox2, Klf4, and cMyc (SKM) suffices for reprogramming mouse somatic cells to induced pluripotent stem cells (iPSCs). Simultaneous induction of Sox2 and cMyc in fibroblasts triggers immediate retroviral silencing, which explains the discrepancy with previous studies that attempted but failed to generate iPSCs without Oct4 using retroviral vectors. SKM induction could partially activate the pluripotency network even in Oct4-knockout fibroblasts. Importantly, reprogramming in the absence of exogenous Oct4 results in greatly improved developmental potential of iPSCs, determined by their ability to give rise to all-iPSC mice in the tetraploid complementation assay. Our data suggest that overexpression of Oct4 during reprogramming leads to off-target gene activation during reprogramming and epigenetic aberrations in resulting iPSCs, and thereby bear major implications for further development and application of iPSC technology.
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