scholarly journals Proviral sequences that restrict retroviral expression in mouse embryonal carcinoma cells.

1987 ◽  
Vol 7 (10) ◽  
pp. 3775-3784 ◽  
Author(s):  
T P Loh ◽  
L L Sievert ◽  
R W Scott
Keyword(s):  
Long Terminal Repeat ◽  
Transient Expression ◽  
Embryonal Carcinoma ◽  
Leukemia Virus ◽  
Terminal Repeat ◽  
Moloney Murine Leukemia Virus ◽  
Primer Binding Site ◽  
Promoter Sequences ◽  
Trna Primer ◽  
Ec Cells

Embryonal carcinoma (EC) cells are nonpermissive for retrovirus replication. Restriction of retroviral expression in EC cells was studied by using DNA transfection techniques. To investigate the activity of the Moloney murine leukemia virus (M-MuLV)enhancer and promoter sequences, the M-MuLV long terminal repeat and the defined long terminal repeat deletions were linked to neo structural gene sequences that encode resistance to the neomycin analog G418. Transient expression data and drug resistance frequencies support the findings that the M-MuLV enhancer is not active in EC cells but that promoter sequences are functional. In addition, a proviral DNA fragment that encodes the leader RNA sequence of a M-MuLV recombinant retrovirus was found to restrict expression specifically in EC cells. Deletion analysis of the leader fragment localized the inhibitory sequences to a region that spans the M-MuLV tRNA primer binding site. It is not known whether restriction occurs at a transcriptional or posttranscriptional level, but steady-state RNA levels in transient expression assays were significantly reduced.

Proviral sequences that restrict retroviral expression in mouse embryonal carcinoma cells

1987 ◽  
Vol 7 (10) ◽  
pp. 3775-3784
Author(s):  
T P Loh ◽  
L L Sievert ◽  
R W Scott
Keyword(s):  
Long Terminal Repeat ◽  
Transient Expression ◽  
Embryonal Carcinoma ◽  
Leukemia Virus ◽  
Terminal Repeat ◽  
Moloney Murine Leukemia Virus ◽  
Primer Binding Site ◽  
Promoter Sequences ◽  
Trna Primer ◽  
Ec Cells

Embryonal carcinoma (EC) cells are nonpermissive for retrovirus replication. Restriction of retroviral expression in EC cells was studied by using DNA transfection techniques. To investigate the activity of the Moloney murine leukemia virus (M-MuLV)enhancer and promoter sequences, the M-MuLV long terminal repeat and the defined long terminal repeat deletions were linked to neo structural gene sequences that encode resistance to the neomycin analog G418. Transient expression data and drug resistance frequencies support the findings that the M-MuLV enhancer is not active in EC cells but that promoter sequences are functional. In addition, a proviral DNA fragment that encodes the leader RNA sequence of a M-MuLV recombinant retrovirus was found to restrict expression specifically in EC cells. Deletion analysis of the leader fragment localized the inhibitory sequences to a region that spans the M-MuLV tRNA primer binding site. It is not known whether restriction occurs at a transcriptional or posttranscriptional level, but steady-state RNA levels in transient expression assays were significantly reduced.

Generation of infectious Moloney murine leukemia viruses with deletions in the U3 portion of the long terminal repeat

1986 ◽  
Vol 6 (12) ◽  
pp. 4634-4640
Author(s):  
R Hanecak ◽  
S Mittal ◽  
B R Davis ◽  
H Fan
Keyword(s):  
Long Terminal Repeat ◽  
Transient Expression ◽  
Leukemia Virus ◽  
Chloramphenicol Acetyltransferase ◽  
Terminal Repeat ◽  
Tata Box ◽  
Moloney Murine Leukemia Virus ◽  
Chloramphenicol Acetyltransferase Gene ◽  
Leukemia Viruses ◽  
Murine Leukemia

Deletional analysis within the long terminal repeat (LTR) of Moloney murine leukemia virus (M-MuLV) was performed. By molecular cloning, deletions were made in the vicinity of the XbaI site at -150 base pairs (bp) in the U3 region, between the tandemly repeated enhancers and the TATA box. The effects of the deletions on LTR function were measured in two ways. First, deleted LTRs were fused to the bacterial chloramphenicol acetyltransferase gene and used in transient expression assays. Second, infectious M-MuLVs were generated by transfection of M-MuLV proviruses containing the deleted LTRs, and the relative infectivity of the mutant viruses was assessed by XC-syncytial assay. Most of the deleted LTRs examined showed relatively high promoter activity in the transient chloramphenicol acetyltransferase assays, with values ranging from 20 to 50% of the wild-type M-MuLV LTR. Thus, the sequences between the enhancers and the TATA box were not absolutely required for transient expression. However, infectivity of viruses carrying the same deleted LTRs showed more pronounced effects. Deletion of sequences from -195 to -174 bp reduced infectivity 20- to 100-fold. Deletion of sequences within the region from -174 to -122 bp did not affect infectivity, indicating that this region is dispensable. On the other hand, deletion of sequences from -150 to -40 bp reduced infectivity from 5 to 6 logs, although the magnitude of the reduction partly may have reflected threshold envelope protein requirements for positive XC assays. The reduced infectivity did not appear to result from a failure of proviral DNA synthesis or integration by the mutant. Thus, the infectivity measurements identified three functional domains in the region between the enhancers and the TATA box.

scholarly journals Mechanism of suppression of the long terminal repeat of Moloney leukemia virus in mouse embryonal carcinoma cells.

1989 ◽  
Vol 9 (11) ◽  
pp. 4670-4676 ◽  
Author(s):  
T Tsukiyama ◽  
O Niwa ◽  
K Yokoro
Keyword(s):  
Long Terminal Repeat ◽  
Cell Lines ◽  
Embryonal Carcinoma ◽  
Binding Protein ◽  
Leukemia Virus ◽  
Chloramphenicol Acetyltransferase ◽  
Terminal Repeat ◽  
Rich Region ◽  
Moloney Leukemia Virus ◽  
Ec Cells

Sequence-specific DNA-binding proteins that bind to the long terminal repeat (LTR) of Moloney leukemia virus in undifferentiated and differentiated mouse embryonal carcinoma (EC) cells were identified by gel retardation assay. The proteins that bind to the CCAAT box were present in both undifferentiated and differentiated EC cells. The amounts and the number of species of the proteins that bind to the enhancer and the GC-rich region were far lower in undifferentiated EC cells than in the differentiated counterparts. These proteins were supposed to be transcriptional activators. Proteins that bind upstream of the enhancer, namely, the -352 to -346 region and the -407 to -404 region, were identified. These proteins were designated the embryonic LTR-binding protein (ELP) and the LTR-binding protein, respectively. The ELP was present only in undifferentiated EC cell lines. The LTR-binding protein was detected in all cell lines tested. The mechanism of suppression of the LTR was investigated by the chloramphenicol acetyltransferase assay. The enhancer and the GC-rich region of the LTR functioned poorly in undifferentiated cells. When eight copies of ELP-binding sequences were inserted upstream of the enhancer region, expression of the chloramphenicol acetyltransferase gene was reduced about threefold in ECA2 cells. From these data, we concluded that two mechanisms, the shortage of activator proteins and the presence of a negative regulatory protein (ELP), are involved in the suppression of the LTR in undifferentiated EC cells.

scholarly journals Generation of infectious Moloney murine leukemia viruses with deletions in the U3 portion of the long terminal repeat.

1986 ◽  
Vol 6 (12) ◽  
pp. 4634-4640 ◽  
Author(s):  
R Hanecak ◽  
S Mittal ◽  
B R Davis ◽  
H Fan
Keyword(s):  
Long Terminal Repeat ◽  
Transient Expression ◽  
Leukemia Virus ◽  
Chloramphenicol Acetyltransferase ◽  
Terminal Repeat ◽  
Tata Box ◽  
Moloney Murine Leukemia Virus ◽  
Chloramphenicol Acetyltransferase Gene ◽  
Leukemia Viruses ◽  
Murine Leukemia

Deletional analysis within the long terminal repeat (LTR) of Moloney murine leukemia virus (M-MuLV) was performed. By molecular cloning, deletions were made in the vicinity of the XbaI site at -150 base pairs (bp) in the U3 region, between the tandemly repeated enhancers and the TATA box. The effects of the deletions on LTR function were measured in two ways. First, deleted LTRs were fused to the bacterial chloramphenicol acetyltransferase gene and used in transient expression assays. Second, infectious M-MuLVs were generated by transfection of M-MuLV proviruses containing the deleted LTRs, and the relative infectivity of the mutant viruses was assessed by XC-syncytial assay. Most of the deleted LTRs examined showed relatively high promoter activity in the transient chloramphenicol acetyltransferase assays, with values ranging from 20 to 50% of the wild-type M-MuLV LTR. Thus, the sequences between the enhancers and the TATA box were not absolutely required for transient expression. However, infectivity of viruses carrying the same deleted LTRs showed more pronounced effects. Deletion of sequences from -195 to -174 bp reduced infectivity 20- to 100-fold. Deletion of sequences within the region from -174 to -122 bp did not affect infectivity, indicating that this region is dispensable. On the other hand, deletion of sequences from -150 to -40 bp reduced infectivity from 5 to 6 logs, although the magnitude of the reduction partly may have reflected threshold envelope protein requirements for positive XC assays. The reduced infectivity did not appear to result from a failure of proviral DNA synthesis or integration by the mutant. Thus, the infectivity measurements identified three functional domains in the region between the enhancers and the TATA box.

Mechanism of suppression of the long terminal repeat of Moloney leukemia virus in mouse embryonal carcinoma cells

1989 ◽  
Vol 9 (11) ◽  
pp. 4670-4676
Author(s):  
T Tsukiyama ◽  
O Niwa ◽  
K Yokoro
Keyword(s):  
Long Terminal Repeat ◽  
Cell Lines ◽  
Embryonal Carcinoma ◽  
Binding Protein ◽  
Leukemia Virus ◽  
Chloramphenicol Acetyltransferase ◽  
Terminal Repeat ◽  
Rich Region ◽  
Moloney Leukemia Virus ◽  
Ec Cells

Sequence-specific DNA-binding proteins that bind to the long terminal repeat (LTR) of Moloney leukemia virus in undifferentiated and differentiated mouse embryonal carcinoma (EC) cells were identified by gel retardation assay. The proteins that bind to the CCAAT box were present in both undifferentiated and differentiated EC cells. The amounts and the number of species of the proteins that bind to the enhancer and the GC-rich region were far lower in undifferentiated EC cells than in the differentiated counterparts. These proteins were supposed to be transcriptional activators. Proteins that bind upstream of the enhancer, namely, the -352 to -346 region and the -407 to -404 region, were identified. These proteins were designated the embryonic LTR-binding protein (ELP) and the LTR-binding protein, respectively. The ELP was present only in undifferentiated EC cell lines. The LTR-binding protein was detected in all cell lines tested. The mechanism of suppression of the LTR was investigated by the chloramphenicol acetyltransferase assay. The enhancer and the GC-rich region of the LTR functioned poorly in undifferentiated cells. When eight copies of ELP-binding sequences were inserted upstream of the enhancer region, expression of the chloramphenicol acetyltransferase gene was reduced about threefold in ECA2 cells. From these data, we concluded that two mechanisms, the shortage of activator proteins and the presence of a negative regulatory protein (ELP), are involved in the suppression of the LTR in undifferentiated EC cells.

scholarly journals Differential disease restriction of Moloney and Friend murine leukemia viruses by the mouse Rmcf gene is governed by the viral long terminal repeat.

1991 ◽  
Vol 174 (2) ◽  
pp. 389-396 ◽  
Author(s):  
B K Brightman ◽  
Q X Li ◽  
D J Trepp ◽  
H Fan
Keyword(s):  
Long Terminal Repeat ◽  
Murine Leukemia Virus ◽  
Time Course ◽  
Leukemia Virus ◽  
Terminal Repeat ◽  
Moloney Murine Leukemia Virus ◽  
Erythroid Progenitors ◽  
Equivalent Time ◽  
Induced Tumors ◽  
Murine Leukemia

Neonatal CxD2 (Rmcfr) and Balb/c (Rmcfs) mice inoculated with Moloney murine leukemia virus (M-MuLV) exhibited approximately equivalent time course and pathology for disease. CxD2 mice showed only slightly reduced presence of Moloney mink cell focus-forming virus (M-MCF) provirus as seen by Southern blot analysis compared to Balb/c mice. This lack of restriction for disease and spread of MCF was in sharp contrast to that seen for CxD2 mice inoculated with Friend murine leukemia virus (F-MuLV), where incidence of disease and propagation of MCFs were severely restricted, as previously reported. Inoculation of CxD2 mice with FM-MuLV, a recombinant F-MuLV virus containing M-MuLV LTR sequences (U3 and R), resulted in T cell disease of time course equal to that seen in Balb/c mice; there also was little restriction for propagation of MCFs. This indicated that presence of the M-MuLV long terminal repeat (LTR) was sufficient for propagation of MCFs in CxD2 mice. Differing restriction for F-MuLV vs. M-MuLV in CxD2 mice was explained on the basis of different "MCF propagator cells" for the two viruses. It was suggested that cells propagating F-MCF (e.g., erythroid progenitors) are blocked by endogenous MCF-like gp70env protein, whereas cells propagating M-MCF (e.g., lymphoid) do not express this protein on their surface. F-MuLV disease in CxD2 mice was greatly accelerated when neonates were inoculated with a F-MuLV/F-MCF pseudotypic mixture. However, F-MCF provirus was not detectable or only barely detectable in F-MuLV/F-MCF-induced tumors, suggesting that F-MCF acted indirectly in induction of these tumors.

scholarly journals A Moloney Murine Leukemia Virus-Based Retrovirus with 4070A Long Terminal Repeat Sequences Induces a High Incidence of Myeloid as Well as Lymphoid Neoplasms

2003 ◽  
Vol 77 (8) ◽  
pp. 4965-4971 ◽  
Author(s):  
Linda Wolff ◽  
Richard Koller ◽  
Xinrong Hu ◽  
Miriam R. Anver
Keyword(s):  
Long Terminal Repeat ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Terminal Repeat ◽  
Moloney Murine Leukemia Virus ◽  
Neoplastic Disease ◽  
Broad Host Range ◽  
Genetically Engineered Mice ◽  
High Incidence ◽  
Murine Leukemia

ABSTRACT Retroviruses can be used to accelerate hematopoietic cancers predisposed to neoplastic disease by prior genetic manipulations such as in transgenic or knockout mice. The virus imparts a second neoplastic “hit,” providing evidence that the initial hit is transforming. In the present study, a unique retrovirus was developed that can induce a high incidence of myeloid disease and has a broad host range. This agent is a Moloney murine leukemia virus (Mo-MuLV)-based virus that has most of the U3 region of the long terminal repeat (LTR) replaced with that of retrovirus 4070A. Like Mo-MuLV, this virus, called MOL4070LTR, is NB-tropic and not restricted by Fv1 allelles. MOL4070LTR causes myeloid leukemias in ca. 50% of mice, a finding in contrast to Mo-MuLV, which induces almost exclusively lymphoid disease. The data suggest that the LTR of the 4070A virus expands the tissue tropism of the disease to the myeloid lineage. Interesting, MCF recombinant envelope was expressed in the lymphoid but not the myeloid neoplasms of BALB/c mice. This retrovirus has the potential for accelerating myeloid disease in genetically engineered mice.

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