Low Expression of YTH Domain-Containing 1 Promotes Microglial M1 Polarization by Reducing the Stability of Sirtuin 1 mRNA

The N6-methyladenosine (m6A) modification is the most abundant posttranscriptional mRNA modification in mammalian cells and is dynamically modulated by a series of “writers,” “erasers,” and “readers.” Studies have shown that m6A affects RNA metabolism in terms of RNA processing, nuclear export, translation, and decay. However, the role of the m6A modification in retinal microglial activation remains unclear. Here, we analyzed the single-cell RNA sequencing data of retinal cells from mice with uveitis and found that the m6A-binding protein YTH domain-containing 1 (YTHDC1) was significantly downregulated in retinal microglia in the context of uveitis. Further studies showed that YTHDC1 deficiency resulted in M1 microglial polarization, an increased inflammatory response and the promotion of microglial migration. Mechanistically, YTHDC1 maintained sirtuin 1 (SIRT1) mRNA stability, which reduced signal transducer and activator of transcription 3 (STAT3) phosphorylation, thus inhibiting microglial M1 polarization. Collectively, our data show that YTHDC1 is critical for microglial inflammatory response regulation and can serve as a target for the development of therapeutics for autogenic immune diseases.

Download Full-text

Modulation of IGF2 Expression in the Murine Thymus and Thymic Epithelial Cells Following Coxsackievirus-B4 Infection

Microorganisms ◽

10.3390/microorganisms9020402 ◽

2021 ◽

Vol 9 (2) ◽

pp. 402

Author(s):

Hélène Michaux ◽

Aymen Halouani ◽

Charlotte Trussart ◽

Chantal Renard ◽

Hela Jaïdane ◽

...

Keyword(s):

Epithelial Cells ◽

Cell Line ◽

Thymic Epithelial Cells ◽

Altered Expression ◽

Coxsackievirus B4 ◽

Gene Coding ◽

Self Tolerance ◽

Stat3 Phosphorylation ◽

The Stability

Coxsackievirus B4 (CV-B4) can infect human and murine thymic epithelial cells (TECs). In a murine TEC cell line, CV-B4 can downregulate the transcription of the insulin-like growth factor 2 (Igf2) gene coding for the self-peptide of the insulin family. In this study, we show that CV-B4 infections of a murine TEC cell line decreased Igf2 P3 promoter activity by targeting a region near the transcription start site; however, the stability of Igf2 transcripts remained unchanged, indicating a regulation of Igf2 transcription. Furthermore, CV-B4 infections decreased STAT3 phosphorylation in vitro. We also showed that mice infected with CV-B4 had an altered expression of Igf2 isoforms as detected in TECs, followed by a decrease in the pro-IGF2 precursor in the thymus. Our study sheds new light on the intrathymic regulation of Igf2 transcription during CV-B4 infections and supports the hypothesis that a viral infection can disrupt central self-tolerance to insulin by decreasing Igf2 transcription in the thymic epithelium.

Download Full-text

Nuclear export of signal recognition particle RNA in mammalian cells

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2003.11.126 ◽

2004 ◽

Vol 313 (2) ◽

pp. 351-355 ◽

Cited By ~ 18

Author(s):

Christina N. Alavian ◽

Joan C. Ritland Politz ◽

Laura B. Lewandowski ◽

Christine M. Powers ◽

Thoru Pederson

Keyword(s):

Nuclear Export ◽

Mammalian Cells ◽

Signal Recognition Particle ◽

Signal Recognition

Download Full-text

Staufen1 is imported into the nucleolus via a bipartite nuclear localization signal and several modulatory determinants

Biochemical Journal ◽

10.1042/bj20050694 ◽

2005 ◽

Vol 393 (1) ◽

pp. 245-254 ◽

Cited By ~ 32

Author(s):

Catherine Martel ◽

Paolo Macchi ◽

Luc Furic ◽

Michael A. Kiebler ◽

Luc Desgroseillers

Keyword(s):

Nuclear Localization ◽

Nuclear Localization Signal ◽

Nuclear Export ◽

Mammalian Cells ◽

Rna Binding ◽

Binding Activity ◽

Nuclear Trafficking ◽

Binding Domains ◽

Bipartite Nuclear Localization Signal ◽

Localization Signal

Mammalian Stau1 (Staufen1), a modular protein composed of several dsRBDs (double-stranded RNA-binding domains), is probably involved in mRNA localization. Although Stau1 is mostly described in association with the rough endoplasmic reticulum and ribosomes in the cytoplasm, recent studies suggest that it may transit through the nucleus/nucleolus. Using a sensitive yeast import assay, we show that Stau1 is actively imported into the nucleus through a newly identified bipartite nuclear localization signal. As in yeast, the bipartite nuclear localization signal is necessary for Stau1 nuclear import in mammalian cells. It is also required for Stau1 nucleolar trafficking. However, Stau1 nuclear transit seems to be regulated by mechanisms that involve cytoplasmic retention and/or facilitated nuclear export. Cytoplasmic retention is mainly achieved through the action of dsRBD3, with dsRBD2 playing a supporting role in this function. Similarly, dsRBD3, but not its RNA-binding activity, is critical for Stau1 nucleolar trafficking. The function of dsRBD3 is strengthened or stabilized by the presence of dsRBD4 but prevented by the interdomain between dsRBD2 and dsRBD3. Altogether, these results suggest that Stau1 nuclear trafficking is a highly regulated process involving several determinants. The presence of Stau1 in the nucleus/nucleolus suggests that it may be involved in ribonucleoprotein formation in the nucleus and/or in other nuclear functions not necessarily related to mRNA transport.

Download Full-text

Probability in transcriptional regulation and its implications for leukocyte differentiation and inducible gene expression

Blood ◽

10.1182/blood.v96.7.2323.h8002323_2323_2328 ◽

2000 ◽

Vol 96 (7) ◽

pp. 2323-2328 ◽

Cited By ~ 2

Author(s):

David A. Hume

Keyword(s):

Gene Expression ◽

Transcriptional Regulation ◽

Mammalian Cells ◽

Cell Lineage ◽

Monoallelic Expression ◽

Stem Cell Lineage ◽

The Stability ◽

Stochastic Phenomena ◽

Inducible Genes ◽

Probabilistic Nature

The phenotype of individual hematopoietic cells, like all other differentiated mammalian cells, is determined by selective transcription of a subset of the genes encoded within the genome. This overview summarizes the recent evidence that transcriptional regulation at the level of individual cells is best described in terms of the regulation of the probability of transcription rather than the rate. In this model, heterogeneous gene expression among populations of cells arises by chance, and the degree of heterogeneity is a function of the stability of the mRNA and protein products of individual genes. The probabilistic nature of transcriptional regulation provides one explanation for stochastic phenomena, such as stem cell lineage commitment, and monoallelic expression of inducible genes, such as lymphokines and cytokines.

Download Full-text

The nuclear pore complex: mediator of translocation between nucleus and cytoplasm

Journal of Cell Science ◽

10.1242/jcs.113.10.1651 ◽

2000 ◽

Vol 113 (10) ◽

pp. 1651-1659 ◽

Cited By ~ 12

Author(s):

T.D. Allen ◽

J.M. Cronshaw ◽

S. Bagley ◽

E. Kiseleva ◽

M.W. Goldberg

Keyword(s):

Nuclear Export ◽

Mammalian Cells ◽

Complex Structure ◽

Nuclear Pore ◽

Nuclear Pore Complexes ◽

Complete Breakdown ◽

Import And Export ◽

Complex Structural ◽

Pore Complexes ◽

Giant Nuclei

The enclosure of nuclear contents in eukaryotes means that cells require sites in the boundary that mediate exchange of material between nucleus and cytoplasm. These sites, termed nuclear pore complexes (NPCs), number 100–200 in yeast, a few thousand in mammalian cells and approximately 50 million in the giant nuclei of amphibian oocytes. NPCs are large (125 MDa) macromolecular complexes that comprise 50–100 different proteins in vertebrates. In spite of their size and complex structure, NPCs undergo complete breakdown and reformation at cell division. Transport through NPCs can be rapid (estimated at several hundred molecules/pore/second) and accommodates both passive diffusion of relatively small molecules, and active transport of complexes up to several megadaltons in molecular mass. Each pore can facilitate both import and export. The two processes apparently involve multiple pathways for different cargoes, and their transport signals, transport receptors and adapters, and the molecules (and their regulators) that underpin the transport mechanisms. Over the past few years there has been an increasing interest in the pore complex: structural studies have been followed by elucidation of the biochemical aspects of nuclear import, and subsequent investigations into nuclear export. The current challenge is to understand the interactions between the structural elements of the pore complex and the mechanisms that drive the physical processes of translocation through it.

Download Full-text

Cytosine methylation dynamics during post-testicular sperm maturation in mammals

10.1101/2020.02.14.949487 ◽

2020 ◽

Author(s):

Carolina Galan ◽

Ryan W. Serra ◽

Fengyun Sun ◽

Vera D. Rinaldi ◽

Colin C. Conine ◽

...

Keyword(s):

Germ Cell ◽

Cytosine Methylation ◽

Reproductive Tract ◽

Extracellular Dna ◽

Cell Populations ◽

Epididymal Sperm ◽

Sequencing Data ◽

Testicular Germ Cell ◽

Mammalian Sperm ◽

The Stability

ABSTRACTBeyond the haploid genome, mammalian sperm contribute a payload of epigenetic information which can modulate offspring phenotypes. Recent studies have shown that the small RNA payload of sperm undergoes extensive remodeling during post-testicular maturation in the epididymis. Intriguingly, epididymal maturation has also been linked to changes in the sperm methylome, suggesting that the epididymis might play a broader role in remodeling the sperm epigenome. Here, we build on prior studies of the maturing sperm methylation landscape, further characterizing the genome-wide methylation landscape in seven germ cell populations collected from throughout the male reproductive tract. Overall, we find very few changes in the cytosine methylation landscape between testicular germ cell populations and cauda epididymal sperm, demonstrating that the sperm methylome is largely stable throughout post-testicular maturation. Intriguingly, although our sequencing data suggested that caput epididymal sperm exhibit a highly unusual methylome, follow-up studies revealed that this resulted from contamination of caput sperm by extracellular DNA. Extracellular DNA formed web-like structures that ensnared sperm, was present only in the caput epididymis of virgin males, where it was associated with citrullinated histone H3 and presumably resulted from a PAD-driven genome decondensation process. Taken together, our data emphasize the stability of the cytosine methylation landscape in mammalian sperm, and identify a surprising but transient period during which immature sperm are associated with extracellular DNA.

Download Full-text

Requirements for the nuclear export of the small ribosomal subunit

Journal of Cell Science ◽

10.1242/jcs.115.14.2985 ◽

2002 ◽

Vol 115 (14) ◽

pp. 2985-2995 ◽

Cited By ~ 4

Author(s):

Terence I. Moy ◽

Pamela A. Silver

Keyword(s):

Nuclear Export ◽

Ribosome Biogenesis ◽

Large Scale ◽

Ribosomal Subunit ◽

Small Subunit ◽

Temperature Sensitive ◽

Yeast Saccharomyces Cerevisiae ◽

Small Ribosomal Subunit ◽

Factors Affecting ◽

The Stability

Eukaryotic ribosome biogenesis requires multiple steps of nuclear transport because ribosomes are assembled in the nucleus while protein synthesis occurs in the cytoplasm. Using an in situ RNA localization assay in the yeast Saccharomyces cerevisiae, we determined that efficient nuclear export of the small ribosomal subunit requires Yrb2, a factor involved in Crm1-mediated export. Furthermore, in cells lacking YRB2, the stability and abundance of the small ribosomal subunit is decreased in comparison with the large ribosomal subunit. To identify additional factors affecting small subunit export, we performed a large-scale screen of temperature-sensitive mutants. We isolated new alleles of several nucleoporins and Ran-GTPase regulators. Together with further analysis of existing mutants,we show that nucleoporins previously shown to be defective in ribosomal assembly are also defective in export of the small ribosomal subunit.

Download Full-text

Dual functions of Rack1 in regulating Hedgehog pathway

Cell Death and Differentiation ◽

10.1038/s41418-020-0563-7 ◽

2020 ◽

Vol 27 (11) ◽

pp. 3082-3096 ◽

Cited By ~ 1

Author(s):

Yan Li ◽

Xiaohan Sun ◽

Dongqing Gao ◽

Yan Ding ◽

Jinxiao Liu ◽

...

Keyword(s):

Mammalian Cells ◽

Cellular Localization ◽

Multiple Roles ◽

Dual Roles ◽

Cubitus Interruptus ◽

Trimeric Complex ◽

Physiological Processes ◽

Underlying Mechanisms ◽

The Stability ◽

Fine Tune

Abstract Hedgehog (Hh) pathway plays multiple roles in many physiological processes and its dysregulation leads to congenital disorders and cancers. Hh regulates the cellular localization of Smoothened (Smo) and the stability of Cubitus interruptus (Ci) to fine-tune the signal outputs. However, the underlying mechanisms are still unclear. Here, we show that the scaffold protein Rack1 plays dual roles in Hh signaling. In the absence of Hh, Rack1 promotes Ci and Cos2 to form a Ci–Rack1–Cos2 complex, culminating in Slimb-mediated Ci proteolysis. In the presence of Hh, Rack1 dissociates from Ci–Rack1–Cos2 complex and forms a trimeric complex with Smo and Usp8, leading to Smo deubiquitination and cell surface accumulation. Furthermore, we find the regulation of Rack1 on Hh pathway is conserved from Drosophila to mammalian cells. Our findings demonstrate that Rack1 plays dual roles during Hh signal transduction and provide Rack1 as a potential drug target for Hh-related diseases.

Download Full-text

HP1γ Sensitizes Cervical Cancer Cells to Cisplatin through the Suppression of UBE2L3

International Journal of Molecular Sciences ◽

10.3390/ijms21175976 ◽

2020 ◽

Vol 21 (17) ◽

pp. 5976 ◽

Cited By ~ 1

Author(s):

Sang Ah Yi ◽

Go Woon Kim ◽

Jung Yoo ◽

Jeung-Whan Han ◽

So Hee Kwon

Keyword(s):

Cervical Cancer ◽

Cancer Cells ◽

Nuclear Export ◽

Nuclear Translocation ◽

Leptomycin B ◽

P53 Signaling ◽

Cervical Cancer Cells ◽

Ubiquitin Conjugating Enzyme ◽

The Stability

Cisplatin is the most frequently used agent for chemotherapy against cervical cancer. However, recurrent use of cisplatin induces resistance, representing a major hurdle in the treatment of cervical cancer. Our previous study revealed that HP1γ suppresses UBE2L3, an E2 ubiquitin conjugating enzyme, thereby enhancing the stability of tumor suppressor p53 specifically in cervical cancer cells. As a follow-up study of our previous findings, here we have identified that the pharmacological substances, leptomycin B and doxorubicin, can improve the sensitivity of cervical cancer cells to cisplatin inducing HP1γ-mediated elevation of p53. Leptomycin B, which inhibits the nuclear export of HP1γ, increased cisplatin-dependent apoptosis induction by promoting the activation of p53 signaling. We also found that doxorubicin, which induces the DNA damage response, promotes HP1γ-mediated silencing of UBE2L3 and increases p53 stability. These effects resulted from the nuclear translocation and binding of HP1γ on the UBE2L3 promoter. Doxorubicin sensitized the cisplatin-resistant cervical cancer cells, enhancing their p53 levels and rate of apoptosis when administered together with cisplatin. Our findings reveal a therapeutic strategy to target a specific molecular pathway that contributes to p53 degradation for the treatment of patients with cervical cancer, particularly with cisplatin resistance.

Download Full-text