Faculty Opinions recommendation of Involvement of a short interspersed element in epigenetic transcriptional silencing of the amoebapore gene in Entamoeba histolytica.

2005 ◽  
Author(s):  
Upinder Singh
Keyword(s):  
Entamoeba Histolytica ◽  
Transcriptional Silencing

scholarly journals Transcriptional Gene Silencing Reveals Two Distinct Groups of Entamoeba histolytica Gal/GalNAc-Lectin Light Subunits

2007 ◽  
Vol 6 (10) ◽  
pp. 1758-1765 ◽  
Author(s):  
Rivka Bracha ◽  
Yael Nuchamowitz ◽  
Nomy Wender ◽  
David Mirelman
Keyword(s):  
Entamoeba Histolytica ◽  
Promoter Region ◽  
Transcriptional Silencing ◽  
Gene Families ◽  
Open Reading Frame ◽  
Transcriptional Gene Silencing ◽  
High Homology ◽  
Crucial Importance ◽  
Reading Frame ◽  
Total Absence

ABSTRACT The Entamoeba histolytica cell surface Gal/GalNAc-inhibitable lectin is a heterodimer between a heavy (170 kDa) subunit linked via a disulfide bond to a light (31 to 35 kDa) subunit. Five light subunit genes with high homology have been identified (Ehlgl1 to -5). We have previously shown that silencing of the expression of Ehlgl1, in the G3 trophozoites which had already been silenced in the amoebapore gene (Ehap-a), also suppressed the transcription of Ehlgl2 and -3 (strain RBV). The total absence of the lgl1 to -3 subunits in the RBV trophozoites affected their ability to cap the surface Gal-lectin molecules to the uroid region. We have now found that in the RBV trophozoites, the lgl4 and -5 subunits (31 kDa) are overexpressed and appear to compensate for the missing lgl1 to -3 in the heterodimer complex. Transcriptional silencing of Ehlgl5 was achieved by transfection of G3 trophozoites with a plasmid containing the open reading frame of Ehlgl5 ligated to the 5′ promoter region of the Ehap-a gene. The transfected trophozoites (strain L5) were silenced in Ehlgl5 and the closely related Ehlgl4, while the expression of the larger lgl1 to -3 subunits was upregulated. L5 trophozoites retained their ability to cap the Gal-lectin molecules. Attempts to simultaneously silence all of the Ehlgl genes have failed so far, possibly due to their crucial importance to the Gal-lectin functions. Our ability to silence part of the genes belonging to the same family can serve as a tool to study the relationships and functions of the members of other gene families.

scholarly journals Involvement of a Short Interspersed Element in Epigenetic Transcriptional Silencing of the Amoebapore Gene in Entamoeba histolytica

2005 ◽  
Vol 4 (11) ◽  
pp. 1775-1784 ◽  
Author(s):  
Michael Anbar ◽  
Rivka Bracha ◽  
Yael Nuchamowitz ◽  
Yan Li ◽  
Anat Florentin ◽  
...  
Keyword(s):  
Entamoeba Histolytica ◽  
Chromatin Immunoprecipitation ◽  
Promoter Region ◽  
Histone H3 ◽  
Transcriptional Silencing ◽  
Regulatory Elements ◽  
Upstream Region ◽  
Antisense Strand ◽  
Interfering Rna

ABSTRACT Transcriptional silencing of an amoebapore (ap-a) gene occurred in Entamoeba histolytica following the transfection of plasmids containing a DNA segment (473 bp) homologous to the 5′ upstream region of the gene (R. Bracha, Y. Nuchamowitz, and D. Mirelman, Eukaryot. Cell 2:295-305, 2003). This segment contains the promoter region of the ap-a gene, a T-rich stretch, followed by a truncated SINE1 (short interspersed element 1) that is transcribed from the antisense strand. Transfection of plasmids containing truncated SINE1 sequences which lack their 3′ regulatory elements upstream of the ap-a gene was essential for the downstream silencing of the ap-a gene while transfection with plasmids containing the entire SINE1 sequence or without the T-rich stretch promoted the overexpression of the ap-a gene. Both the T-rich stretch and sequences of the 5′ SINE1 were essential for the transcription of SINE1. RNA extracts from gene-silenced cultures showed small amounts of short (∼140-nucleotide), single-stranded molecules with homology to SINE1 but no short interfering RNA. Chromatin immunoprecipitation analysis with an antibody against methylated K4 of histone H3 showed a demethylation of K4 at the domain of the ap-a gene, indicating transcriptional inactivation. These results suggest the involvement of SINE1 in triggering the gene silencing and the role of histone modification in its epigenetic maintenance.

scholarly journals Transcriptional Silencing of Multiple Genes in Trophozoites of Entamoeba histolytica

2006 ◽  
Vol 2 (5) ◽  
pp. e48 ◽  
Author(s):  
Rivka Bracha ◽  
Yael Nuchamowitz ◽  
Michael Anbar ◽  
David Mirelman
Keyword(s):  
Entamoeba Histolytica ◽  
Transcriptional Silencing ◽  
Multiple Genes

scholarly journals tRNA Gene Sequences Are Required for Transcriptional Silencing in Entamoeba histolytica

2009 ◽  
Vol 9 (2) ◽  
pp. 306-314 ◽  
Author(s):  
Henriette Irmer ◽  
Ina Hennings ◽  
Iris Bruchhaus ◽  
Egbert Tannich
Keyword(s):  
Entamoeba Histolytica ◽  
Trna Gene ◽  
Regulation Of Gene Expression ◽  
Transcriptional Silencing ◽  
Protozoan Parasite ◽  
Upstream Region ◽  
Trna Genes ◽  
Intestinal Protozoan ◽  
Content Type ◽  
Systematic Assessment

ABSTRACT Transcriptional silencing by trans inactivation can contribute to the regulation of gene expression in eukaryotic cells. In the human intestinal protozoan parasite Entamoeba histolytica, trans inactivation of the amoebapore-A gene (AP-A) was recently achieved by episomal transfection of E. histolytica trophozoites with the plasmid psAP1. The mechanism of AP-A trans inactivation is largely unknown, though it was suggested that a partial short interspersed transposable element (SINE) is required. By systematic assessment of various E. histolytica isolates transfected with psAP1 derivates, trans inactivation of AP-A was restricted to the strain HM-1:IMSS (2411) but could not be achieved in other standard laboratory strains. Importantly, sequences of an E. histolytica tRNA array that were located on psAP1 in close proximity to the AP-A upstream region and comprising the glutamic acid (TTC) (E) and tyrosine (GTA) (Y) tRNA genes were indispensable for AP-A silencing. In contrast to the case described in previous reports, SINE was not required for AP-A trans inactivation. AP-A expression could be regained in silenced cells by episomal transfection under the control of a heterologous E. histolytica promoter, opening a way toward future silencing of individual genes of interest in E. histolytica. Our results indicate that tRNA gene-mediated silencing is not restricted to Saccharomyces cerevisiae.

scholarly journals Transcriptional Silencing of an Amoebapore Gene in Entamoeba histolytica: Molecular Analysis and Effect on Pathogenicity

2003 ◽  
Vol 2 (2) ◽  
pp. 295-305 ◽  
Author(s):  
Rivka Bracha ◽  
Yael Nuchamowitz ◽  
David Mirelman
Keyword(s):  
Gene Silencing ◽  
Entamoeba Histolytica ◽  
Transcription Initiation ◽  
Transcriptional Silencing ◽  
Upstream Region ◽  
Transcriptional Gene Silencing ◽  
Plasmid Construct ◽  
Gene Coding ◽  
Rna Fragments ◽  
Flanking Sequences

ABSTRACT Transcriptional silencing of the gene coding for amoebapore A (AP-A) was observed when trophozoites of Entamoeba histolytica were transfected with a hybrid plasmid construct containing the ap-a gene flanked by the upstream and downstream segments of the original Ehap-a gene. Transfectants were totally devoid of ap-a transcript and AP-A protein. An identical silencing effect was observed upon transfection with a plasmid that contained only the 5′ upstream region of ap-a. Removal of the selecting antibiotic enabled the isolation of plasmidless clones, which retained in their progeny the silenced phenotype. E. histolytica cells were able to overexpress ap-a when transfected with a plasmid containing the gene flanked by the 5′ and 3′ regions of the EhRP-L21 gene. This plasmid, however, could not express ap-a in the retransfected, cloned trophozoites lacking AP-A. This is the first report of gene silencing in E. histolytica, and the mechanism appears to belong to transcriptional gene silencing and not to posttranscriptional gene silencing. This conclusion is based on the following results: (i) silencing was achieved by transfection of homologous 5′ flanking sequences (470 bp of the Ehap-a gene), (ii) transcription initiation of Ehap-a was found to be blocked, and (iii) short double-stranded RNA fragments of the ap-a coding and noncoding sequences were not detected. Trophozoites lacking AP-A are nonpathogenic and impaired in their bacteriolytic capability.

Erythrophagocytosis by Entamoeba histolytica.- Ultrastructural Study

1972 ◽  
Vol 30 ◽  
pp. 156-157 ◽  
Author(s):  
Norberto Treviño ◽  
Alfredo Feria-Velasco ◽  
I. Ruiz de Chávez
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Entamoeba Histolytica ◽  
Ultrastructural Study ◽  
Saline Solution ◽  
Physiological Saline ◽  
Ultrastructural Level ◽  
Hot Plate ◽  
Physiological Saline Solution ◽  
Axenic Conditions

Although erythrophagocytosis by various species of Entamoeba is a well known phenomenon this has not yet been studied in detail at the ultrastructural level. The present work deals with the description of the incorporation process of erythrocytes by trophozoites of E. histolytica. For this study, trophozoites of E. histolytica, HK-9:NIH strain cultured in axenic conditions and washed human erythrocytes were placed on a hot plate at 37°C in physiological saline solution. After 5 minutes, 2.5% glutarldehyde was added and the samples were processed according to conventional techniques for electron microscopy.Based upon light microscopy studies on living trophozoites in contact with erythrocytes, it seems that erythrophagocytosis only takes place in one pole of the parasite.

Scanning electron microscopy of erythrophagocytosis by Entamoeba histolytica trophozoites

1992 ◽  
Vol 50 (1) ◽  
pp. 880-881
Author(s):  
Victor Tsutsumi ◽  
Adolfo Martinez-Palomo ◽  
Kyuichi Tanikawa
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Red Blood Cells ◽  
Entamoeba Histolytica ◽  
Causative Agent ◽  
Blood Cells ◽  
Protozoan Parasite ◽  
Complex Phenomenon ◽  
Great Capacity ◽  
Scanning Electron

The protozoan parasite Entamoeba histolytica is the causative agent of amebiasis in man. The trophozoite or motile form is a highly dynamic and pleomorphic cell with a great capacity to destroy tissues. Moreover, the parasite has the singular ability to phagocytize a variety of different live or death cells. Phagocytosis of red blood cells by E. histolytica trophozoites is a complex phenomenon related with amebic pathogenicity and nutrition.

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