scholarly journals Tertiary Structural and Functional Analyses of a Viroid RNA Motif by Isostericity Matrix and Mutagenesis Reveal Its Essential Role in Replication

2006 ◽  
Vol 80 (17) ◽  
pp. 8566-8581 ◽  
Author(s):  
Xuehua Zhong ◽  
Neocles Leontis ◽  
Shuiming Qian ◽  
Asuka Itaya ◽  
Yijun Qi ◽  
...  
Keyword(s):  
Essential Role ◽  
Tertiary Structure ◽  
Matrix Analysis ◽  
Base Pairs ◽  
Rna Motifs ◽  
Viroid Infection ◽  
Functional Analyses

ABSTRACT RNA-templated RNA replication is essential for viral or viroid infection, as well as for regulation of cellular gene expression. Specific RNA motifs likely regulate various aspects of this replication. Viroids of the Pospiviroidae family, as represented by the Potato spindle tuber viroid (PSTVd), replicate in the nucleus by utilizing DNA-dependent RNA polymerase II. We investigated the role of the loop E (sarcin/ricin) motif of the PSTVd genomic RNA in replication. A tertiary-structural model of this motif, inferred by comparative sequence analysis and comparison with nuclear magnetic resonance and X-ray crystal structures of loop E motifs in other RNAs, is presented in which core non-Watson-Crick base pairs are precisely specified. Isostericity matrix analysis of these base pairs showed that the model accounts for the reported natural sequence variations and viable experimental mutations in loop E motifs of PSTVd and other viroids. Furthermore, isostericity matrix analysis allowed us to design disruptive, as well as compensatory, mutations of PSTVd loop E. Functional analyses of such mutants by in vitro and in vivo experiments demonstrated that loop E structural integrity is crucial for replication, specifically during transcription. Our results suggest that the PSTVd loop E motif exists and functions in vivo and provide loss-of-function genetic evidence for the essential role of a viroid RNA three-dimensional motif in rolling-circle replication. The use of isostericity matrix analysis of non-Watson-Crick base pairing to rationalize mutagenesis of tertiary motifs and systematic in vitro and in vivo functional assays of mutants offers a novel, comprehensive approach to elucidate the tertiary-structure-function relationships for RNA motifs of general biological significance.

Cellular Samurai: katanin and the severing of microtubules

2000 ◽  
Vol 113 (16) ◽  
pp. 2821-2827 ◽  
Author(s):  
L. Quarmby
Keyword(s):  
Epithelial Cells ◽  
Essential Role ◽  
Aaa Atpase ◽  
C Elegans ◽  
Microtubule Severing ◽  
Biochemical Studies ◽  
New Evidence

Recent biochemical studies of the AAA ATPase, katanin, provide a foundation for understanding how microtubules might be severed along their length. These in vitro studies are complemented by a series of recent reports of direct in vivo observation of microtubule breakage, which indicate that the in vitro phenomenon of catalysed microtubule severing is likely to be physiological. There is also new evidence that microtubule severing by katanin is important for the production of non-centrosomal microtubules in cells such as neurons and epithelial cells. Although it has been difficult to establish the role of katanin in mitosis, new genetic evidence indicates that a katanin-like protein, MEI-1, plays an essential role in meiosis in C. elegans. Finally, new proteins involved in the severing of axonemal microtubules have been discovered in the deflagellation system of Chlamydomonas.

scholarly journals Essential Role of Chromatin Assembly Factor-1–mediated Rapid Nucleosome Assembly for DNA Replication and Cell Division in Vertebrate Cells

2007 ◽  
Vol 18 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Yasunari Takami ◽  
Tatsuya Ono ◽  
Tatsuo Fukagawa ◽  
Kei-ichi Shibahara ◽  
Tatsuo Nakayama
Keyword(s):  
Dna Replication ◽  
Essential Role ◽  
Chromatin Assembly ◽  
Nuclear Antigen ◽  
Nucleosome Assembly ◽  
Chromatin Assembly Factor ◽  
Assembly Factor

Chromatin assembly factor-1 (CAF-1), a complex consisting of p150, p60, and p48 subunits, is highly conserved from yeast to humans and facilitates nucleosome assembly of newly replicated DNA in vitro. To investigate roles of CAF-1 in vertebrates, we generated two conditional DT40 mutants, respectively, devoid of CAF-1p150 and p60. Depletion of each of these CAF-1 subunits led to delayed S-phase progression concomitant with slow DNA synthesis, followed by accumulation in late S/G2 phase and aberrant mitosis associated with extra centrosomes, and then the final consequence was cell death. We demonstrated that CAF-1 is necessary for rapid nucleosome formation during DNA replication in vivo as well as in vitro. Loss of CAF-1 was not associated with the apparent induction of phosphorylations of S-checkpoint kinases Chk1 and Chk2. To elucidate the precise role of domain(s) in CAF-1p150, functional dissection analyses including rescue assays were preformed. Results showed that the binding abilities of CAF-1p150 with CAF-1p60 and DNA polymerase sliding clamp proliferating cell nuclear antigen (PCNA) but not with heterochromatin protein HP1-γ are required for cell viability. These observations highlighted the essential role of CAF-1–dependent nucleosome assembly in DNA replication and cell proliferation through its interaction with PCNA.

scholarly journals Autoamplification of NFATc1 expression determines its essential role in bone homeostasis

2005 ◽  
Vol 202 (9) ◽  
pp. 1261-1269 ◽  
Author(s):  
Masataka Asagiri ◽  
Kojiro Sato ◽  
Takako Usami ◽  
Sae Ochi ◽  
Hiroshi Nishina ◽  
...  
Keyword(s):  
Essential Role ◽  
Osteoclast Differentiation ◽  
Ectopic Expression ◽  
Epigenetic Mechanism ◽  
Bone Homeostasis ◽  
Hematopoietic Stem ◽  
Vitro Effect

NFATc1 and NFATc2 are functionally redundant in the immune system, but it was suggested that NFATc1 is required exclusively for differentiation of osteoclasts in the skeletal system. Here we provide genetic evidence that NFATc1 is essential for osteoclast differentiation in vivo by adoptive transfer of NFATc1−/− hematopoietic stem cells to osteoclast-deficient Fos−/− mice, and by Fos−/− blastocyst complementation, thus avoiding the embryonic lethality of NFATc1−/− mice. However, in vitro osteoclastogenesis in NFATc1-deficient cells was rescued by ectopic expression of NFATc2. The discrepancy between the in vivo essential role of NFATc1 and the in vitro effect of NFATc2 was attributed to selective autoregulation of the NFATc1 gene by NFAT through its promoter region. This suggested that an epigenetic mechanism contributes to the essential function of NFATc1 in cell lineage commitment. Thus, this study establishes that NFATc1 represents a potential therapeutic target for bone disease and reveals a mechanism that underlies the essential role of NFATc1 in bone homeostasis.

scholarly journals HOXA10 mediates epithelial-mesenchymal transition to promote gastric cancer metastasis partly via modulation of TGFB2/Smad/METTL3 signaling axis

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Chenlong Song ◽  
Chongzhi Zhou
Keyword(s):  
Gastric Cancer ◽  
Western Blot ◽  
Lung Metastasis ◽  
Essential Role ◽  
Luciferase Reporter ◽  
Migration And Invasion ◽  
Signaling Axis

Abstract Background Homeobox A10 (HOXA10) belongs to the HOX gene family, which plays an essential role in embryonic development and tumor progression. We previously demonstrated that HOXA10 was significantly upregulated in gastric cancer (GC) and promoted GC cell proliferation. This study was designed to investigate the role of HOXA10 in GC metastasis and explore the underlying mechanism. Methods Immunohistochemistry (IHC) was used to evaluate the expression of HOXA10 in GC. In vitro cell migration and invasion assays as well as in vivo mice metastatic models were utilized to investigate the effects of HOXA10 on GC metastasis. GSEA, western blot, qRT-PCR and confocal immunofluorescence experiments preliminarily analyzed the relationship between HOXA10 and EMT. ChIP-qPCR, dual-luciferase reporter (DLR), co-immunoprecipitation (CoIP), colorimetric m6A assay and mice lung metastasis rescue models were performed to explore the mechanism by which HOXA10 accelerated the EMT process in GC. Results In this study, we demonstrated HOXA10 was upregulated in GC patients and the difference was even more pronounced in patients with lymph node metastasis (LNM) than without. Functionally, HOXA10 promoted migration and invasion of GC cells in vitro and accelerated lung metastasis in vivo. EMT was an important mechanism responsible for HOXA10-involved metastasis. Mechanistically, we revealed HOXA10 enriched in the TGFB2 promoter region, promoted transcription, increased secretion, thus triggered the activation of TGFβ/Smad signaling with subsequent enhancement of Smad2/3 nuclear expression. Moreover, HOXA10 upregulation elevated m6A level and METTL3 expression in GC cells possible by regulating the TGFB2/Smad pathway. CoIP and ChIP-qPCR experiments demonstrated that Smad proteins played an important role in mediating METTL3 expression. Furthermore, we found HOXA10 and METTL3 were clinically relevant, and METTL3 was responsible for the HOXA10-mediated EMT process by performing rescue experiments with western blot and in vivo mice lung metastatic models. Conclusions Our findings indicated the essential role of the HOXA10/TGFB2/Smad/METTL3 signaling axis in GC progression and metastasis.

Phenotypic and functional analyses of dendritic cells in patients with lymphoproliferative disease of granular lymphocytes (LDGL)

Blood ◽  
2005 ◽  
Vol 106 (12) ◽  
pp. 3926-3931 ◽  
Author(s):  
Renato Zambello ◽  
Tamara Berno ◽  
Giovanna Cannas ◽  
Ilenia Baesso ◽  
Gianni Binotto ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Specific Antigen ◽  
Cell Types ◽  
Lymphoproliferative Disease ◽  
Topographic Organization ◽  
Functional Analyses ◽  
Granular Lymphocytes

We investigated whether dendritic cells (DCs) play a role in favoring granular lymphocyte (GL) proliferation in patients with lymphoproliferative disease of granular lymphocytes (LDGL). The presence of in vivo circulating DCs was studied in 11 patients (5 CD3+ and 6 CD3- LDGL). Autologous immature (iDCs) and mature (mDCs) DCs generated in vitro were studied for stimulatory activity on cell proliferation of CD3+ and CD3- GLs. The topographic organization of GLs and DCs was also studied in bone marrow (BM) biopsies. Peripheral blood (PB) CD3- GLs from patients showed significant proliferative activity in the presence of iDCs and mDCs. Conversely, monoclonal CD3+ GLs were unresponsive to autologous and allogeneic PB DCs. Analysis of BM biopsies demonstrated a topographic distribution of DCs and GLs that indicates contact between the 2 cell types. On functional assays, DCs obtained from BM were more efficient than PB DCs in stimulating CD3- GLs, and surprisingly, a low but definite stimulatory effect was demonstrated also on CD3+ GLs. The putative contact between DCs and GLs in the BM and, more crucial, the proliferative response of discrete GL populations to DC stimulation suggest the presence of a specific antigen within BM DCs, providing evidence for a role of DCs in the pathogenesis of LDGL.

scholarly journals Fusion Competence of Myoblasts Rendered Genetically Null for N-Cadherin in Culture

1997 ◽  
Vol 138 (2) ◽  
pp. 331-336 ◽  
Author(s):  
Carol A. Charlton ◽  
William A. Mohler ◽  
Glenn L. Radice ◽  
Richard O. Hynes ◽  
Helen M. Blau
Keyword(s):  
Essential Role ◽  
Myoblast Fusion ◽  
Surface Adhesion ◽  
Adult Mice ◽  
General Importance ◽  
Primary Myoblasts ◽  
Muscle Formation

Myoblast fusion is essential to muscle tissue development yet remains poorly understood. N-cadherin, like other cell surface adhesion molecules, has been implicated by others in muscle formation based on its pattern of expression and on inhibition of myoblast aggregation and fusion by antibodies or peptide mimics. Mice rendered homozygous null for N-cadherin revealed the general importance of the molecule in early development, but did not test a role in skeletal myogenesis, since the embryos died before muscle formation. To test genetically the proposed role of N-cadherin in myoblast fusion, we successfully obtained N-cadherin null primary myoblasts in culture. Fusion of myoblasts expressing or lacking N-cadherin was found to be equivalent, both in vitro by intracistronic complementation of lacZ and in vivo by injection into the muscles of adult mice. An essential role for N-cadherin in mediating the effects of basic fibroblast growth factor was also excluded. These methods for obtaining genetically homozygous null somatic cells from adult tissues should have broad applications. Here, they demonstrate clearly that the putative fusion molecule, N-cadherin, is not essential for myoblast fusion.

scholarly journals CRIg plays an essential role in intravascular clearance of bloodborne parasites by interacting with complement

2019 ◽  
Vol 116 (48) ◽  
pp. 24214-24220 ◽  
Author(s):  
Gongguan Liu ◽  
Yong Fu ◽  
Mohammed Yosri ◽  
Yanli Chen ◽  
Peng Sun ◽  
...  
Keyword(s):  
Essential Role ◽  
Parasitic Infection ◽  
Complement C3 ◽  
Critical Question ◽  
Independent Manner ◽  
African Trypanosomes ◽  
Recognition Receptor

Although CRIg was originally identified as a macrophage receptor for binding complement C3b/iC3b in vitro, recent studies reveal that CRIg functions as a pattern recognition receptor in vivo for Kupffer cells (KCs) to directly bind bacterial pathogens in a complement-independent manner. This raises the critical question of whether CRIg captures circulating pathogens through interactions with complement in vivo under flow conditions. Furthermore, the role of CRIg during parasitic infection is unknown. Taking advantage of intravital microscopy and using African trypanosomes as a model, we studied the role of CRIg in intravascular clearance of bloodborne parasites. Complement C3 is required for intravascular clearance of African trypanosomes by KCs, preventing the early mortality of infected mice. Moreover, antibodies are essential for complement-mediated capture of circulating parasites by KCs. Interestingly, reduced antibody production was observed in the absence of complement C3 during infection. We further demonstrate that CRIg but not CR3 is critically involved in KC-mediated capture of circulating parasites, accounting for parasitemia control and host survival. Of note, CRIg cannot directly catch circulating parasites and antibody-induced complement activation is indispensable for CRIg-mediated parasite capture. Thus, we provide evidence that CRIg, by interacting with complement in vivo, plays an essential role in intravascular clearance of bloodborne parasites. Targeting CRIg may be considered as a therapeutic strategy.

scholarly journals Effect of ACTH and hCG on the Expression of Gonadotropin-Inducible Ovarian Transcription Factor 1 (Giot1) Gene in the Rat Adrenal Gland

2018 ◽  
Vol 19 (8) ◽  
pp. 2285 ◽  
Author(s):  
Karol Jopek ◽  
Marianna Tyczewska ◽  
Manjunath Ramanjaneya ◽  
Marta Szyszka ◽  
Piotr Celichowski ◽  
...  
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Transcription Factor ◽  
Adrenal Gland ◽  
Essential Role ◽  
Rat Adrenals ◽  
Transcription Factor 1

Gonadotropin-inducible ovarian transcription factor-1 (Giot1) belongs to a family of fast-responsive genes, and gonadotropins rapidly induce its expression in steroidogenic cells of ovaries and testes of rats. Gonadal Giot1 gene expression is regulated by cyclic adenosine monophosphate (cAMP) -dependent protein kinase A pathway, with essential role of orphan nuclear receptor NR4A1 transcription factor (nuclear receptor subfamily 4, group A, member 1). A recent study reports that Giot1 is also expressed in adrenals, however, the mechanism of its regulation in adrenal gland is yet to be identified. Therefore, the aim of this study was to characterise the changes in Giot1 gene expression in male and female rat adrenals using wide range of in vivo and in vitro experimental models. Special emphasis was directed at the Giot1 gene regulation by ACTH and gonadotropin. In our study, we found that ACTH rapidly stimulates Giot1 expression both in vivo and in vitro. However, gonadotropin does not affect the adrenal Giot1 gene expression, presumably due to the low expression of gonadotropin receptor in adrenals. Both testosterone and estradiol administered in vivo had inhibitory effect on Giot1 gene expression in the adrenals of post-gonadectomized adult rats. Further, our studies revealed that the intracellular mechanism of Giot1 gene regulation in rat adrenals is similar to that of gonads. As in the case of gonads, the expression of Giot1 in adrenal gland is regulated by cAMP-dependent signaling pathway with essential role of the NR4A1 transcription factor. The results of our studies suggest that Giot1 may be involved in the regulation of rat adrenocortical steroidogenesis.

scholarly journals Menin enhances c-Myc-mediated transcription to promote cancer progression

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Gongwei Wu ◽  
Mengqiu Yuan ◽  
Shengqi Shen ◽  
Xiaoyu Ma ◽  
Jingwen Fang ◽  
...  
Keyword(s):  
Cancer Progression ◽  
Essential Role ◽  
Target Genes ◽  
Dependent Manner ◽  
Regulatory Factor ◽  
E Box ◽  
Unique Ability

Abstract Menin is an enigmatic protein that displays unique ability to either suppress or promote tumorigenesis in a context-dependent manner. The role for Menin to promote oncogenic functions has been largely attributed to its essential role in forming the MLL methyltransferase complex, which mediates H3K4me3. Here, we identify an unexpected role of Menin in enhancing the transactivity of oncogene MYC in a way independent of H3K4me3 activity. Intriguingly, we find that Menin interacts directly with the TAD domain of MYC and co-localizes with MYC to E-Box to enhance the transcription of MYC target genes in a P-TEFb-dependent manner. We further demonstrate that, by transcriptionally promoting the expression of MYC target genes in cancer cells, Menin stimulates cell proliferation and cellular metabolism both in vitro and in vivo. Our results uncover a previously unappreciated mechanism by which Menin functions as an oncogenic regulatory factor that is critical for MYC-mediated gene transcription.

Sign in / Sign up

Export Citation Format

Share Document