Reacquisition of a functional early region by a mouse transformant containing only defective simian virus 40 DNA

1984 ◽  
Vol 4 (4) ◽  
pp. 666-670
Author(s):  
S Chen ◽  
G Blanck ◽  
R Pollack
Keyword(s):  
Molecular Weight ◽  
Viral Protein ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
T Antigens ◽  
Viral Dna ◽  
Molecular Weights ◽  
Early Region ◽  
Mouse Cells

Viral DNA in simian virus 40-transformed mouse cells is capable of rearranging with passage. In this report, we show that such rearrangement can include an alteration in viral protein expression. SVT2, a simian virus 40-transformed mouse BALB/c 3T3 cell line, synthesizes only a super T antigen of molecular weight 100,000 without synthesizing the lytic-size large T or small t antigens with molecular weights of 94,000 and 17,000, respectively. Analyses of the integrated viral DNA revealed an early region of 4.4 kilobases instead of the lytic-size 2.7 kilobases. However, upon subcloning in either plastic or agarose or after being in culture for several passages, the appearance of lytic-size large T and small t antigens was detected. Concurrently, an early region of 2.7 kilobases, in addition to one of 4.4 kilobases, was observed.

scholarly journals Reacquisition of a functional early region by a mouse transformant containing only defective simian virus 40 DNA.

1984 ◽  
Vol 4 (4) ◽  
pp. 666-670 ◽  
Author(s):  
S Chen ◽  
G Blanck ◽  
R Pollack
Keyword(s):  
Molecular Weight ◽  
Viral Protein ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
T Antigens ◽  
Viral Dna ◽  
Molecular Weights ◽  
Early Region ◽  
Mouse Cells

Viral DNA in simian virus 40-transformed mouse cells is capable of rearranging with passage. In this report, we show that such rearrangement can include an alteration in viral protein expression. SVT2, a simian virus 40-transformed mouse BALB/c 3T3 cell line, synthesizes only a super T antigen of molecular weight 100,000 without synthesizing the lytic-size large T or small t antigens with molecular weights of 94,000 and 17,000, respectively. Analyses of the integrated viral DNA revealed an early region of 4.4 kilobases instead of the lytic-size 2.7 kilobases. However, upon subcloning in either plastic or agarose or after being in culture for several passages, the appearance of lytic-size large T and small t antigens was detected. Concurrently, an early region of 2.7 kilobases, in addition to one of 4.4 kilobases, was observed.

scholarly journals Unusual regulation of simian virus 40 early-region transcription in genomes containing two origins of DNA replication.

1984 ◽  
Vol 4 (9) ◽  
pp. 1915-1928 ◽  
Author(s):  
A R Buchman ◽  
P Berg
Keyword(s):  
Dna Replication ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type Virus ◽  
Animal Cells ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Early Region ◽  
Inverted Duplication

As part of our efforts to create multifunctional vectors for the transduction of animal cells, a set of simian virus 40 recombinants were constructed which contain an inverted duplication of the region including the origin of viral DNA replication (ori) and the early-region promoter. The unusual aspects of the structure of these recombinant genomes revealed several unexpected features of their function. In particular, transcription from the early-region promoters on these recombinants occurred primarily after the start of DNA replication, and, in that sense, these promoters behaved as if they were late-region promoters. This behavior results from the fact that these genomes contain multiple ori segments, and, therefore, they replicate earlier and faster than wild-type virus DNA, thereby causing a precocious shift in the initiation of early-region transcription from sites downstream of ori to sites located upstream of ori. The abnormal expression from multiple ori genomes is consistent with our present notions regarding the replication-dependent shift in early-region transcriptional start sites (Buchman et al., Mol. Cell. Biol. 4:1900-1914). Since our experiments demonstrate that RNAs initiated upstream of ori contribute to T-antigen formation late in infection, we suggest that the shift in early-region transcription starts modulates large T-antigen production in concert with viral DNA replication.

Unusual regulation of simian virus 40 early-region transcription in genomes containing two origins of DNA replication

1984 ◽  
Vol 4 (9) ◽  
pp. 1915-1928
Author(s):  
A R Buchman ◽  
P Berg
Keyword(s):  
Dna Replication ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type Virus ◽  
Animal Cells ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Early Region ◽  
Inverted Duplication

As part of our efforts to create multifunctional vectors for the transduction of animal cells, a set of simian virus 40 recombinants were constructed which contain an inverted duplication of the region including the origin of viral DNA replication (ori) and the early-region promoter. The unusual aspects of the structure of these recombinant genomes revealed several unexpected features of their function. In particular, transcription from the early-region promoters on these recombinants occurred primarily after the start of DNA replication, and, in that sense, these promoters behaved as if they were late-region promoters. This behavior results from the fact that these genomes contain multiple ori segments, and, therefore, they replicate earlier and faster than wild-type virus DNA, thereby causing a precocious shift in the initiation of early-region transcription from sites downstream of ori to sites located upstream of ori. The abnormal expression from multiple ori genomes is consistent with our present notions regarding the replication-dependent shift in early-region transcriptional start sites (Buchman et al., Mol. Cell. Biol. 4:1900-1914). Since our experiments demonstrate that RNAs initiated upstream of ori contribute to T-antigen formation late in infection, we suggest that the shift in early-region transcription starts modulates large T-antigen production in concert with viral DNA replication.

Complex regulation of simian virus 40 early-region transcription from different overlapping promoters

1984 ◽  
Vol 4 (9) ◽  
pp. 1900-1914
Author(s):  
A R Buchman ◽  
M Fromm ◽  
P Berg
Keyword(s):  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Large T Antigen ◽  
T Antigens ◽  
Upstream Side ◽  
Early Region ◽  
Origin Of Dna Replication ◽  
Template Dna ◽  
Enhancer Sequences

During simian virus 40 lytic infection there is a shift in initiation sites used to transcribe the early region, which encodes large T and small t antigens. Early in infection, transcription is initiated almost exclusively from sites that are downstream of the origin of DNA replication, whereas transcripts produced later are initiated mainly from sites on the upstream side. We have used mutant virus and specially constructed plasmid DNAs to investigate the factors regulating this transcriptional shift. In our studies simian virus 40 large T antigen appears to mediate the shift in transcription in two ways: first, T antigen represses transcription at the downstream sites late in infection by binding to the region where these RNAs are initiated; second, T antigen promotes transcription from sites on the upstream side by its ability to initiate replication or amplification, or both, of the template DNA. In addition, transcription from the downstream sites is heavily dependent on enhancer sequences located in the 72-base-pair repeat region, whereas transcription from the upstream sites late in infection does not require enhancer sequences. Thus, different overlapping promoters regulate simian virus 40 early-region expression in a manner that apparently coordinates the production of large T antigen with the increase in viral DNA.

Efficient transformation of human fibroblasts by adenovirus-simian virus 40 recombinants

1984 ◽  
Vol 4 (8) ◽  
pp. 1653-1656
Author(s):  
K Van Doren ◽  
Y Gluzman
Keyword(s):  
Cell Lines ◽  
Human Fibroblasts ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Origin Of Replication ◽  
Viral Dna ◽  
Early Region ◽  
Transformed Cell Lines ◽  
Sv40 Dna

The origin-defective simian virus 40 (SV40) mutant 6-1 has been useful in transforming human cells (Small et al., Nature [London] 296:671-672, 1982; Nagata et al., Nature [London] 306:597-599, 1983). However, the low efficiency of transformation achieved by DNA transfection is a major drawback of the system. To increase the efficiency of SV40-induced transformation of human fibroblasts, we used recombinant adenovirus-SV40 virions which contain a complete SV40 early region including either a wild-type or defective (6-1) origin of replication. The SV40 DNA was cloned into the adenovirus vector in place of early region 1. Cell lines transformed by viruses containing a functional origin of replication produced free SV40 DNA. These cell lines were subcloned, and some of the subclones lost the ability to produce free viral DNA. Subclones that failed to produce free viral DNA were found to possess a mutated T antigen. Cell lines transformed by viruses containing origin-defective SV40 mutants did not produce any free DNA. Because of the high efficiency of transformation, we suggest that the origin-defective chimeric virus is a convenient system for establishing SV40-transformed cell lines from any human cell type that is susceptible to infection by adenovirus type 5.

scholarly journals Complex regulation of simian virus 40 early-region transcription from different overlapping promoters.

1984 ◽  
Vol 4 (9) ◽  
pp. 1900-1914 ◽  
Author(s):  
A R Buchman ◽  
M Fromm ◽  
P Berg
Keyword(s):  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Large T Antigen ◽  
T Antigens ◽  
Upstream Side ◽  
Early Region ◽  
Origin Of Dna Replication ◽  
Template Dna ◽  
Enhancer Sequences

During simian virus 40 lytic infection there is a shift in initiation sites used to transcribe the early region, which encodes large T and small t antigens. Early in infection, transcription is initiated almost exclusively from sites that are downstream of the origin of DNA replication, whereas transcripts produced later are initiated mainly from sites on the upstream side. We have used mutant virus and specially constructed plasmid DNAs to investigate the factors regulating this transcriptional shift. In our studies simian virus 40 large T antigen appears to mediate the shift in transcription in two ways: first, T antigen represses transcription at the downstream sites late in infection by binding to the region where these RNAs are initiated; second, T antigen promotes transcription from sites on the upstream side by its ability to initiate replication or amplification, or both, of the template DNA. In addition, transcription from the downstream sites is heavily dependent on enhancer sequences located in the 72-base-pair repeat region, whereas transcription from the upstream sites late in infection does not require enhancer sequences. Thus, different overlapping promoters regulate simian virus 40 early-region expression in a manner that apparently coordinates the production of large T antigen with the increase in viral DNA.

scholarly journals Efficient transformation of human fibroblasts by adenovirus-simian virus 40 recombinants.

1984 ◽  
Vol 4 (8) ◽  
pp. 1653-1656 ◽  
Author(s):  
K Van Doren ◽  
Y Gluzman
Keyword(s):  
Cell Lines ◽  
Human Fibroblasts ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Origin Of Replication ◽  
Viral Dna ◽  
Early Region ◽  
Transformed Cell Lines ◽  
Sv40 Dna

The origin-defective simian virus 40 (SV40) mutant 6-1 has been useful in transforming human cells (Small et al., Nature [London] 296:671-672, 1982; Nagata et al., Nature [London] 306:597-599, 1983). However, the low efficiency of transformation achieved by DNA transfection is a major drawback of the system. To increase the efficiency of SV40-induced transformation of human fibroblasts, we used recombinant adenovirus-SV40 virions which contain a complete SV40 early region including either a wild-type or defective (6-1) origin of replication. The SV40 DNA was cloned into the adenovirus vector in place of early region 1. Cell lines transformed by viruses containing a functional origin of replication produced free SV40 DNA. These cell lines were subcloned, and some of the subclones lost the ability to produce free viral DNA. Subclones that failed to produce free viral DNA were found to possess a mutated T antigen. Cell lines transformed by viruses containing origin-defective SV40 mutants did not produce any free DNA. Because of the high efficiency of transformation, we suggest that the origin-defective chimeric virus is a convenient system for establishing SV40-transformed cell lines from any human cell type that is susceptible to infection by adenovirus type 5.

scholarly journals A truncated T antigen expressed from an alternatively spliced BK virus early mRNA

2009 ◽  
Vol 90 (5) ◽  
pp. 1238-1245 ◽  
Author(s):  
Johanna R. Abend ◽  
Amy E. Joseph ◽  
Dweepanita Das ◽  
Deniz B. Campbell-Cecen ◽  
Michael J. Imperiale
Keyword(s):  
Jc Virus ◽  
Stop Codon ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Bk Virus ◽  
T Antigens ◽  
Reading Frame ◽  
Early Region ◽  
Alternatively Spliced

The early region of BK virus (BKV) is known to encode two well-characterized tumour (T) antigens, large T antigen (TAg) and small T antigen (tAg). In this study, we provide evidence of a third early BKV mRNA that codes for an additional early region product with an apparent molecular mass of 17–20 kDa. This truncated form of TAg (truncTAg) is expressed from an alternatively spliced mRNA that is derived from the excision of a second intron from the mRNA encoding TAg. The first 133 aa of truncTAg are identical to those of TAg but the additional splice results in translation from a different reading frame, adding three new amino acids before reaching a stop codon. TruncTAg is expressed in both BKV-transformed and lytically infected cells and it is found to be primarily localized to the nucleus. The function of BKV truncTAg is likely to be relevant to transformation, similar to the additional T antigens of simian virus 40, JC virus and mouse polyomavirus.

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