scholarly journals MicroRNA miR-128 represses LINE-1 (L1) retrotransposition by downregulating the nuclear import factor TNPO1

2017 ◽  
Author(s):  
Adam Idica ◽  
Evgueni A Sevrioukov ◽  
Dimitri G Zisoulis ◽  
Matthias Hamdorf ◽  
Iben Daugaard ◽  
...  
Keyword(s):  
Nuclear Import ◽  
Molecular Mechanisms ◽  
Somatic Cells ◽  
Cellular Proteins ◽  
Additional Restriction ◽  
Protein Factor ◽  
Repressive Effect ◽  
Rnp Complex ◽  
Direct Binding ◽  
L1 Element

ABSTRACTRepetitive elements, including LINE-1 (L1), comprise approximately half of the human genome. These elements can potentially destabilize the genome by initiating their own replication and reintegration into new sites (retrotransposition). In somatic cells, transcription of L1 elements are repressed by distinct molecular mechanisms including DNA methylation and histone modifications to repress transcription. Under conditions of hypomethylation (e.g. in tumor cells) a window of opportunity for L1 de-repression arises and additional restriction mechanisms become crucial. We recently demonstrated that the microRNA miR-128 represses L1 activity by directly binding to L1 ORF2 RNA. In this study, we tested whether miR-128 can also control L1 activity by repressing cellular proteins important for L1 retrotransposition. We found that miR-128 targets the 3’UTR of the nuclear import factor transportin 1 (TNPO1) mRNA. Manipulation of miR-128 and TNPO1 levels demonstrated that induction or depletion of TNPO1 affects L1 retrotransposition and nuclear import of an L1-RNP complex (using L1-encoded ORF1p as a proxy for L1-RNP complexes). Moreover, TNPO1 overexpression partially reversed the repressive effect of miR-128 on L1 retrotransposition. Our study represents the first description of a protein factor involved in nuclear import of the L1 element and demonstrates that miR-128 controls L1 activity in somatic cells through two independent mechanisms: direct binding to L1 RNA, and regulating a cellular factor necessary for L1 nuclear import and retrotransposition.

scholarly journals Bone remodeling stages under physiological conditions and glucocorticoid in excess: Focus on cellular and molecular mechanisms

2021 ◽  
Vol 12 (2) ◽  
pp. 212-227
Author(s):  
V. V. Povoroznyuk ◽  
N. V. Dedukh ◽  
M. A. Bystrytska ◽  
V. S. Shapovalov
Keyword(s):  
Growth Factors ◽  
Bone Resorption ◽  
Signaling Pathways ◽  
Bone Remodeling ◽  
Molecular Mechanisms ◽  
Signaling Molecules ◽  
Physiological Conditions ◽  
Bone Cell Differentiation ◽  
Repressive Effect

This review provides a rationale for the cellular and molecular mechanisms of bone remodeling stages under physiological conditions and glucocorticoids (GCs) in excess. Remodeling is a synchronous process involving bone resorption and formation, proceeding through stages of: (1) resting bone, (2) activation, (3) bone resorption, (4) reversal, (5) formation, (6) termination. Bone remodeling is strictly controlled by local and systemic regulatory signaling molecules. This review presents current data on the interaction of osteoclasts, osteoblasts and osteocytes in bone remodeling and defines the role of osteoprogenitor cells located above the resorption area in the form of canopies and populating resorption cavities. The signaling pathways of proliferation, differentiation, viability, and cell death during remodeling are presented. The study of signaling pathways is critical to understanding bone remodeling under normal and pathological conditions. The main signaling pathways that control bone resorption and formation are RANK / RANKL / OPG; M-CSF – c-FMS; canonical and non-canonical signaling pathways Wnt; Notch; MARK; TGFβ / SMAD; ephrinB1/ephrinB2 – EphB4, TNFα – TNFβ, and Bim – Bax/Bak. Cytokines, growth factors, prostaglandins, parathyroid hormone, vitamin D, calcitonin, and estrogens also act as regulators of bone remodeling. The role of non-encoding microRNAs and long RNAs in the process of bone cell differentiation has been established. MicroRNAs affect many target genes, have both a repressive effect on bone formation and activate osteoblast differentiation in different ways. Excess of glucocorticoids negatively affects all stages of bone remodeling, disrupts molecular signaling, induces apoptosis of osteocytes and osteoblasts in different ways, and increases the life cycle of osteoclasts. Glucocorticoids disrupt the reversal stage, which is critical for the subsequent stages of remodeling. Negative effects of GCs on signaling molecules of the canonical Wingless (WNT)/β-catenin pathway and other signaling pathways impair osteoblastogenesis. Under the influence of excess glucocorticoids biosynthesis of biologically active growth factors is reduced, which leads to a decrease in the expression by osteoblasts of molecules that form the osteoid. Glucocorticoids stimulate the expression of mineralization inhibitor proteins, osteoid mineralization is delayed, which is accompanied by increased local matrix demineralization. Although many signaling pathways involved in bone resorption and formation have been discovered and described, the temporal and spatial mechanisms of their sequential turn-on and turn-off in cell proliferation and differentiation require additional research.

scholarly journals Adult Neural Stem Cells: Basic Research and Production Strategies for Neurorestorative Therapy

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
E. M. Samoilova ◽  
V. A. Kalsin ◽  
N. M. Kushnir ◽  
D. A. Chistyakov ◽  
A. V. Troitskiy ◽  
...  
Keyword(s):  
Stem Cells ◽  
Neural Stem Cells ◽  
Nervous Tissue ◽  
Molecular Mechanisms ◽  
Somatic Cells ◽  
Basic Research ◽  
Neural Cells ◽  
Pluripotent State ◽  
Increased Risk ◽  
Object Of Study

Over many decades, constructing genetically and phenotypically stable lines of neural stem cells (NSC) for clinical purposes with the aim of restoring irreversibly lost functions of nervous tissue has been one of the major goals for multiple research groups. The unique ability of stem cells to maintain their own pluripotent state even in the adult body has made them into the choice object of study. With the development of the technology for induced pluripotent stem cells (iPSCs) and direct transdifferentiation of somatic cells into the desired cell type, the initial research approaches based on the use of allogeneic NSCs from embryonic or fetal nervous tissue are gradually becoming a thing of the past. This review deals with basic molecular mechanisms for maintaining the pluripotent state of embryonic/induced stem and reprogrammed somatic cells, as well as with currently existing reprogramming strategies. The focus is on performing direct reprogramming while bypassing the stage of iPSCs which is known for genetic instability and an increased risk of tumorigenesis. A detailed description of various protocols for obtaining reprogrammed neural cells used in the therapy of the nervous system pathology is also provided.

Molecular Mechanisms of Plant Regeneration

2019 ◽  
Vol 70 (1) ◽  
pp. 377-406 ◽  
Author(s):  
Momoko Ikeuchi ◽  
David S. Favero ◽  
Yuki Sakamoto ◽  
Akira Iwase ◽  
Duncan Coleman ◽  
...  
Keyword(s):  
Cell Fate ◽  
Molecular Mechanisms ◽  
Normal Development ◽  
Somatic Cells ◽  
Cell Fates ◽  
Developmental Programs ◽  
Hormonal Responses ◽  
Wound Stress ◽  
Directional Transport

Plants reprogram somatic cells following injury and regenerate new tissues and organs. Upon perception of inductive cues, somatic cells often dedifferentiate, proliferate, and acquire new fates to repair damaged tissues or develop new organs from wound sites. Wound stress activates transcriptional cascades to promote cell fate reprogramming and initiate new developmental programs. Wounding also modulates endogenous hormonal responses by triggering their biosynthesis and/or directional transport. Auxin and cytokinin play pivotal roles in determining cell fates in regenerating tissues and organs. Exogenous application of these plant hormones enhances regenerative responses in vitro by facilitating the activation of specific developmental programs. Many reprogramming regulators are epigenetically silenced during normal development but are activated by wound stress and/or hormonal cues.

scholarly journals Nuclear Import of Cdk/Cyclin Complexes: Identification of Distinct Mechanisms for Import of Cdk2/Cyclin E and Cdc2/Cyclin B1

1999 ◽  
Vol 144 (2) ◽  
pp. 213-224 ◽  
Author(s):  
Jonathan D. Moore ◽  
Jing Yang ◽  
Ray Truant ◽  
Sally Kornbluth
Keyword(s):  
Nuclear Localization ◽  
Nuclear Import ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Cyclin E ◽  
Cyclin B1 ◽  
Transport Processes ◽  
Nuclear Localization Sequence ◽  
Nuclear Targeting ◽  
Importin Α

Reversible phosphorylation of nuclear proteins is required for both DNA replication and entry into mitosis. Consequently, most cyclin-dependent kinase (Cdk)/cyclin complexes are localized to the nucleus when active. Although our understanding of nuclear transport processes has been greatly enhanced by the recent identification of nuclear targeting sequences and soluble nuclear import factors with which they interact, the mechanisms used to target Cdk/cyclin complexes to the nucleus remain obscure; this is in part because these proteins lack obvious nuclear localization sequences. To elucidate the molecular mechanisms responsible for Cdk/cyclin transport, we examined nuclear import of fluorescent Cdk2/cyclin E and Cdc2/cyclin B1 complexes in digitonin-permeabilized mammalian cells and also examined potential physical interactions between these Cdks, cyclins, and soluble import factors. We found that the nuclear import machinery recognizes these Cdk/cyclin complexes through direct interactions with the cyclin component. Surprisingly, cyclins E and B1 are imported into nuclei via distinct mechanisms. Cyclin E behaves like a classical basic nuclear localization sequence–containing protein, binding to the α adaptor subunit of the importin-α/β heterodimer. In contrast, cyclin B1 is imported via a direct interaction with a site in the NH2 terminus of importin-β that is distinct from that used to bind importin-α.

scholarly journals Nuclear transport of U1 snRNP in somatic cells: differences in signal requirement compared with Xenopus laevis oocytes.

1994 ◽  
Vol 125 (5) ◽  
pp. 971-980 ◽  
Author(s):  
U Fischer ◽  
J Heinrich ◽  
K van Zee ◽  
E Fanning ◽  
R Lührmann
Keyword(s):  
Xenopus Laevis ◽  
Nuclear Import ◽  
Nuclear Transport ◽  
Somatic Cells ◽  
Xenopus Laevis Oocytes ◽  
Xenopus Laevis Oocyte ◽  
Nuclear Targeting ◽  
Transport Pathway ◽  
U1 Snrnp

The signal requirement for the nuclear import of U1 RNA in somatic cells from different species was investigated by microinjection of both digoxygenin-labeled wild type and mutant U1 RNA molecules and in vitro reconstituted U1 snRNPs. U1 RNA was shown to be targeted to the nucleus by a temperature-dependent process that requires the prior assembly of RNPs from the common proteins and the microinjected RNA. Competition in the cell between immunoaffinity-purified U1 snRNPs and digoxygenin-labeled U1 snRNPs reconstituted in vitro showed that the transport is saturable and should therefore be a mediated process. The transport of a karyophilic protein under the same conditions was not affected, indicating the existence of a U snRNP-specific transport pathway in somatic cells, as already seen in the Xenopus laevis oocyte system. Surprisingly, the signal requirement for nuclear transport of U1 snRNP was found to differ between oocytes and somatic cells from mouse, monkey and Xenopus, in that the m3GGpppG-cap is no longer an essential signaling component in somatic cells. However, as shown by investigation of the transport kinetics of m3GpppG- and ApppG-capped U1 snRNPs, the m3GpppG-cap accelerates the rate of U1 snRNP import significantly indicating that it has retained a signaling role for nuclear targeting of U1 snRNP in somatic cells. Moreover, our data strongly suggest that cell specific rather than species specific differences account for the differential m3G-cap requirement in nuclear import of U1 snRNPs.

scholarly journals Pluripotency and nuclear reprogramming

2008 ◽  
Vol 363 (1500) ◽  
pp. 2079-2087 ◽  
Author(s):  
Shinya Yamanaka
Keyword(s):  
Stem Cells ◽  
Molecular Mechanisms ◽  
Potential Problem ◽  
Somatic Cells ◽  
Embryonic Stem ◽  
Donor Cell ◽  
Human Embryos ◽  
Cell Sources ◽  
Cell Transplantation Therapy ◽  
Transplantation Therapy

Embryonic stem cells are promising donor cell sources for cell transplantation therapy, which may in the future be used to treat various diseases and injuries. However, as is the case for organ transplantation, immune rejection after transplantation is a potential problem with this type of therapy. Moreover, the use of human embryos presents serious ethical difficulties. These issues may be overcome if pluripotent stem cells are generated from patients' somatic cells. Here, we review the molecular mechanisms underlying pluripotency and the currently known methods of inducing pluripotency in somatic cells.

scholarly journals Recurrent losses and rapid evolution of the condensin II complex in insectsg

2018 ◽  
Author(s):  
T. King ◽  
C.J. Leonard ◽  
J.C. Cooper ◽  
S. Nguyen ◽  
E. Joyce ◽  
...  
Keyword(s):  
Genome Organization ◽  
Molecular Mechanisms ◽  
Somatic Cells ◽  
Rapid Evolution ◽  
Genetic Material ◽  
Life Forms ◽  
Model Organisms ◽  
Homologous Chromosomes ◽  
Homologous Chromosome Pairing ◽  
Key Aspects

AbstractCondensins play a crucial role in the organization of genetic material by compacting and disentangling chromosomes. The condensin I and condensin II complexes are widely considered to have distinct functions based on studies in a few model organisms, although the specific functions of each complex are yet to be fully understood. The condensin II complex is critical for genome organization in Drosophila, and is a key anti-pairing factor that separates homologous chromosomes in somatic cells. Intriguingly, the Cap-G2 subunit of condensin II is absent in Drosophila melanogaster, and this loss may be related to the high levels of homologous chromosome pairing in somatic cells seen in flies. Here, we find that this Cap-G2 loss predates the origin of Dipterans, and other CapG2 losses have occurred independently in multiple insect lineages. Furthermore, the Cap-H2 and Cap-D3 subunits have also been repeatedly and independently lost in several insect orders, and some taxa lack condensin II-specific subunits entirely. We used Oligopaint DNA-FISH to quantify pairing levels in ten species across seven orders, representing several different configurations of the condensin II complex. We find that all non-Dipteran insects display near-uniform low pairing levels, suggesting that some key aspects of genome organization are robust to condensin II subunit losses. Finally, we observe consistent signatures of positive selection in condensin II subunits across flies and mammals. These findings suggest that these ancient complexes are far more evolutionarily labile than previously suspected, and are at the crossroads of several forms of genomic conflicts. Our results raise fundamental questions about the specific functions of the two condensin complexes and the interplay between them in taxa that have experienced subunit losses, and open the door to further investigations to elucidate the diversity of molecular mechanisms that underlie genome organization across various life forms.

scholarly journals Effect of Different Nuclear Localization Signals on the Subcellular Localization and Anti-HIV-1 Function of the MxB Protein

2021 ◽  
Vol 12 ◽  
Author(s):  
Keli Chai ◽  
Zhen Wang ◽  
Qinghua Pan ◽  
Juan Tan ◽  
Wentao Qiao ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Nuclear Import ◽  
Molecular Mechanisms ◽  
Virus Production ◽  
Viral Capsid ◽  
Terminal Sequence ◽  
Nuclear Localization Signals ◽  
Localization Signal ◽  
Anti Hiv ◽  
Hiv 1

Interferon exerts its antiviral activity by stimulating the expression of antiviral proteins. These interferon stimulate genes (ISGs) often target a group of viruses with unique molecular mechanisms. One such ISG is myxovirus resistance B (MxB) that has been reported to inhibit human immunodeficiency virus type 1 (HIV-1) by targeting viral capsid and impairing nuclear import of viral DNA. The antiviral specificity of MxB is determined by its N-terminal 25 amino acids sequence which has the nuclear localization activity, therefore functions as a nuclear localization signal (NLS). In this study, we report that the bipartite NLS, but not the classic NLS, the PY-NLS, nor the arginine-rich NLS, when used to replace the N-terminal sequence of MxB, drastically suppress HIV-1 gene expression and virus production, thus creates a new anti-HIV-1 mechanism. MxB preserves its anti-HIV-1 activity when its N-terminal sequence is replaced by the arginine-rich NLS. Interestingly, the arginine-rich NLS allows MxB to inhibit HIV-1 CA mutants that are otherwise resistant to wild type MxB, which suggests sequence specific targeting of viral capsid. Together, these data implicate that it is not the nuclear import function itself, but rather the sequence and the mechanism of action of the NLS which define the antiviral property of MxB.

scholarly journals Autoregulation of the human C/EBP alpha gene by stimulation of upstream stimulatory factor binding.

1995 ◽  
Vol 15 (3) ◽  
pp. 1192-1202 ◽  
Author(s):  
N Timchenko ◽  
D R Wilson ◽  
L R Taylor ◽  
S Abdelsayed ◽  
M Wilde ◽  
...  
Keyword(s):  
Human Gene ◽  
Gene Promoter ◽  
Cell Types ◽  
Upstream Stimulatory Factor ◽  
Cis Element ◽  
Protein Factor ◽  
Direct Binding ◽  
Alpha Gene ◽  
A Site ◽  
Stimulatory Factor

The human C/EBP alpha gene promoter shares significant sequence homology with that of the mouse but has a different mechanism of autoregulation. Activation of the murine promoter by direct binding of C/EBP alpha to a site within 200 bp of the transcriptional start was shown to elevate activity by approximately threefold (R. J. Christy, K. H. Kaestner, D. E. Geiman, and M. D. Lane, Proc. Natl. Acad. Sci. USA 88:2593-2597, 1991; K. Legraverend, P. Antonson, P. Flodby, and K. G. Xanthapoulos, Nucleic Acids Res. 21:1735-1742, 1993). Unlike its murine counterpart, the human C/EBP alpha gene promoter does not contain a cis element that binds the C/EBP alpha protein. Neither C/EBP alpha nor C/EBP beta (NF-Il-6) binds the human C/EBP alpha promoter within 437 bp. However, cotransfection studies show that C/EBP alpha stimulates transcription of a reporter gene driven by 437 bp of the C/EBP alpha promoter. Our studies show that the human C/EBP alpha protein stimulates USF to bind to a USF consensus element within C/EBP alpha promoter and activates it by two- to threefold. We propose that the human gene employs the ubiquitously expressed DNA-binding protein factor USF to carry out autoregulation. Autoregulation of the human C/EBP alpha promoter was abolished by deletion of the USF binding site, CACGTG. Expression of human C/EBP beta following transfection did not stimulate USF binding. These studies suggest a mechanism whereby tissue-specific autoregulation can be achieved via a trans-acting factor that is expressed in all cell types. Thus, direct binding of the C/EBP alpha protein to the promoter of the C/EBP alpha gene is not required for autoregulation.

Close spatio-association of the transient receptor potential canonical 4 (TRPC4) channel with Gαi in TRPC4 activation process

2015 ◽  
Vol 308 (11) ◽  
pp. C879-C889 ◽  
Author(s):  
JongYun Myeong ◽  
Misun Kwak ◽  
Jae-Pyo Jeon ◽  
Chansik Hong ◽  
Ju-hong Jeon ◽  
...  
Keyword(s):  
G Protein ◽  
Molecular Mechanisms ◽  
Transient Receptor Potential ◽  
Hek293 Cells ◽  
Activation Process ◽  
Mutant Form ◽  
Muscarinic Agonist ◽  
Direct Binding ◽  
Fret Efficiency ◽  
Trpc4 Channel

TPRC channels are Ca2+-permeable, nonselective cation channels that are activated by a wide variety of stimuli, including G protein-coupled receptors (GPCRs). TRPC4 is commonly assumed to be activated by Gq/phospholipase C-coupled receptors. However, the other molecular mechanisms by which Gα proteins regulate TRPC4 remain unclear. Here, we found that Gαi2 regulates TRPC4 activation by direct binding. To investigate this mechanism, we used whole patch clamp and fluorescence resonance energy transfer (FRET). We tagged an isoform of mTRPC4 and G protein with CFP and YFP, respectively, and transiently transfected cells with the FRET pair. The FRET efficiency between TRPC4β-CFP and the constitutively active mutant form of Gαi2 was nearly 15% and was greater than that observed with wild-type Gαi2 (nearly 5%). Gβγ and the TRPC4 channel showed a FRET efficiency lower than 6%. In HEK293 cells transfected with the M2 muscarinic receptor, the application of carbachol increased the FRET efficiency between TRPC4β-CFP and Gαi2(WT)-YFP from 4.7 ± 0.4% ( n = 7) to 12.6 ± 1.4% ( n = 7). We also found that the TRPC4 channel directly interacts with Gαi2, but not with Gαq, when the channel is open. We analyzed the calcium levels in HEK293 cells expressing the channels and Gαi2 or Gαq using the calcium indicator YC6.1 (Yellow Cameleon 6.1). In response to the muscarinic agonist carbachol, M2-, Gαi2-, and TRPC4-expressing cells showed a prolonged Ca2+ influx compared with cells expressing only M2. Together, these data suggest that Gαi2 activates the TRPC4 channel by direct binding, which then induces Ca2+ entry.

Sign in / Sign up

Export Citation Format

Share Document