scholarly journals Evidence for a stem cell-specific repressor of Moloney murine leukemia virus expression in embryonal carcinoma cells.

1990 ◽  
Vol 10 (8) ◽  
pp. 4045-4057 ◽  
Author(s):  
T P Loh ◽  
L L Sievert ◽  
R W Scott
Keyword(s):  
Stem Cell ◽  
Base Pair ◽  
Murine Leukemia Virus ◽  
Embryonal Carcinoma ◽  
Leukemia Virus ◽  
Binding Activity ◽  
Moloney Murine Leukemia Virus ◽  
Nuclear Extracts ◽  
Ec Cells ◽  
Murine Leukemia

A negative regulatory element (NRE) spanning the tRNA primer-binding site (PBS) of Moloney murine leukemia virus (M-MuLV) mediates repression of M-MuLV expression specifically in embryonal carcinoma (EC) cells. We precisely defined the element by base-pair mutagenesis to an 18-base-pair segment of the tRNA PBS and showed that the element also restricted expression when moved upstream of the long terminal repeat. A DNA-binding activity specific for the M-MuLV NRE was detected in vitro by using crude EC nuclear extracts in exonuclease III protection assays. Binding was strongly correlated with repression in EC cells. Mutations within the NRE that relieved repression disrupted binding activity. Also, nuclear extracts prepared from permissive, differentiated EC cell cultures showed reduced binding activity for the NRE. These results indicate the presence of a stem cell-specific repressor that extinguishes M-MuLV expression via the NRE at the tRNA PBS.

Evidence for a stem cell-specific repressor of Moloney murine leukemia virus expression in embryonal carcinoma cells

1990 ◽  
Vol 10 (8) ◽  
pp. 4045-4057
Author(s):  
T P Loh ◽  
L L Sievert ◽  
R W Scott
Keyword(s):  
Stem Cell ◽  
Base Pair ◽  
Murine Leukemia Virus ◽  
Embryonal Carcinoma ◽  
Leukemia Virus ◽  
Binding Activity ◽  
Moloney Murine Leukemia Virus ◽  
Nuclear Extracts ◽  
Ec Cells ◽  
Murine Leukemia

A negative regulatory element (NRE) spanning the tRNA primer-binding site (PBS) of Moloney murine leukemia virus (M-MuLV) mediates repression of M-MuLV expression specifically in embryonal carcinoma (EC) cells. We precisely defined the element by base-pair mutagenesis to an 18-base-pair segment of the tRNA PBS and showed that the element also restricted expression when moved upstream of the long terminal repeat. A DNA-binding activity specific for the M-MuLV NRE was detected in vitro by using crude EC nuclear extracts in exonuclease III protection assays. Binding was strongly correlated with repression in EC cells. Mutations within the NRE that relieved repression disrupted binding activity. Also, nuclear extracts prepared from permissive, differentiated EC cell cultures showed reduced binding activity for the NRE. These results indicate the presence of a stem cell-specific repressor that extinguishes M-MuLV expression via the NRE at the tRNA PBS.

scholarly journals Six distinct nuclear factors interact with the 75-base-pair repeat of the Moloney murine leukemia virus enhancer

1987 ◽  
Vol 7 (3) ◽  
pp. 1101-1110 ◽  
Author(s):  
N A Speck ◽  
D Baltimore
Keyword(s):  
Cell Lines ◽  
Base Pair ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Simian Virus 40 ◽  
Moloney Murine Leukemia Virus ◽  
Nuclear Extracts ◽  
Nuclear Factors ◽  
Binding Factor ◽  
Murine Leukemia

Binding sites for six distinct nuclear factors on the 75-base-pair repeat of the Moloney murine leukemia virus enhancer have been identified by an electrophoretic mobility shift assay combined with methylation interference. Three of these factors, found in WEHI 231 nuclear extracts, which we have named LVa, LVb, and LVc (for leukemia virus factors a, b, and c) have not been previously identified. Nuclear factors that bind to the conserved simian virus 40 corelike motif, the NF-1 motif, and the glucocorticoid response element were also detected. Testing of multiple cell lines showed that most factors appeared ubiquitous, except that the NF-1 binding factor was found neither in nuclear extracts from MEL cells nor in the embryonal carcinoma cell lines PCC4 and F9, and core-binding factor was relatively depleted from MEL and F9 nuclear extracts.

scholarly journals Six distinct nuclear factors interact with the 75-base-pair repeat of the Moloney murine leukemia virus enhancer.

1987 ◽  
Vol 7 (3) ◽  
pp. 1101-1110 ◽  
Author(s):  
N A Speck ◽  
D Baltimore
Keyword(s):  
Cell Lines ◽  
Base Pair ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Simian Virus 40 ◽  
Moloney Murine Leukemia Virus ◽  
Nuclear Extracts ◽  
Nuclear Factors ◽  
Binding Factor ◽  
Murine Leukemia

Binding sites for six distinct nuclear factors on the 75-base-pair repeat of the Moloney murine leukemia virus enhancer have been identified by an electrophoretic mobility shift assay combined with methylation interference. Three of these factors, found in WEHI 231 nuclear extracts, which we have named LVa, LVb, and LVc (for leukemia virus factors a, b, and c) have not been previously identified. Nuclear factors that bind to the conserved simian virus 40 corelike motif, the NF-1 motif, and the glucocorticoid response element were also detected. Testing of multiple cell lines showed that most factors appeared ubiquitous, except that the NF-1 binding factor was found neither in nuclear extracts from MEL cells nor in the embryonal carcinoma cell lines PCC4 and F9, and core-binding factor was relatively depleted from MEL and F9 nuclear extracts.

scholarly journals Transcriptional Silencing of Moloney Murine Leukemia Virus in Human Embryonic Carcinoma Cells

2016 ◽  
Vol 91 (1) ◽  
Author(s):  
Gary Z. Wang ◽  
Stephen P. Goff
Keyword(s):  
Gene Expression ◽  
Murine Leukemia Virus ◽  
Cellular Differentiation ◽  
Leukemia Virus ◽  
Transcriptional Silencing ◽  
Moloney Murine Leukemia Virus ◽  
Histone Marks ◽  
Embryonic Carcinoma ◽  
Ec Cells ◽  
Murine Leukemia

ABSTRACT Embryonic carcinoma (EC) cells are malignant counterparts of embryonic stem (ES) cells and serve as useful models for investigating cellular differentiation and human embryogenesis. Though the susceptibility of murine EC cells to retroviral infection has been extensively analyzed, few studies of retrovirus infection of human EC cells have been performed. We tested the susceptibility of human EC cells to transduction by retroviral vectors derived from three different retroviral genera. We show that human EC cells efficiently express reporter genes delivered by vectors based on human immunodeficiency virus type 1 (HIV-1) and Mason-Pfizer monkey virus (M-PMV) but not Moloney murine leukemia virus (MLV). In human EC cells, MLV integration occurs normally, but no viral gene expression is observed. The block to MLV expression of MLV genomes is relieved upon cellular differentiation. The lack of gene expression is correlated with transcriptional silencing of the MLV promoter through the deposition of repressive histone marks as well as DNA methylation. Moreover, depletion of SETDB1, a histone methyltransferase, resulted in a loss of transcriptional silencing and upregulation of MLV gene expression. Finally, we provide evidence showing that the lack of MLV gene expression may be attributed in part to the lack of MLV enhancer function in human EC cells. IMPORTANCE Human embryonic carcinoma (EC) cells are shown to restrict the expression of murine leukemia virus genomes but not retroviral genomes of the lentiviral or betaretroviral families. The block occurs at the level of transcription and is accompanied by the deposition of repressive histone marks and methylation of the integrated proviral DNA. The host machinery required for silencing in human EC cells is distinct from that in murine EC cell lines: the histone methyltransferase SETDB1 is required, but the widely utilized corepressor TRIM28/Kap1 is not. A transcriptional enhancer element from the Mason-Pfizer monkey virus can override the silencing and promote transcription of chimeric proviral DNAs. The findings reveal novel features of human EC gene regulation not present in their murine counterparts.

Characterization of the Moloney Murine Leukemia Virus Stem Cell-Specific Repressor Binding Site

Virology ◽  
1993 ◽  
Vol 193 (2) ◽  
pp. 690-699 ◽  
Author(s):  
Geraldine Kempler ◽  
Breton Freitag ◽  
Brent Berwin ◽  
Oliver Nanassy ◽  
Eric Barklis
Keyword(s):  
Stem Cell ◽  
Binding Site ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Moloney Murine Leukemia Virus ◽  
Repressor Binding Site ◽  
Murine Leukemia
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