Recombination induces tandem repeats of integrated viral sequences in polyoma-transformed cells

Friderici, Karen; Oh, Saw Yin; Ellis, Ronald J.; Guacci, Vincent; Fluck, Michele M.

doi:10.1016/0042-6822(84)90009-6

Cited by 13 publications

(8 citation statements)

References 14 publications

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“…A second minor site of hybridization was also detected over chromosome 15, band D3. T h e results are in line with previous studies showing integration of polyoma viral sequences at a major site in transformed rat cells (Friderici et al, 1984). Our findings of specific polyoma integration sites together with the detection by in situ hybridization of numerous polyoma DNA sequences in about half of the cell nuclei of both primary tumors and cultured tumor cells indicate that polyoma sequences are present both as integrated and as free viral DNA.…”

Section: Discussionsupporting

confidence: 93%

Karyotypic instability and viral integration in polyoma virus‐induced mouse salivary gland tumors

Sandros

Stenman

1990

Genes Chromosomes & Cancer

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Stable integration of polyoma viral DNA into the host-cell genome is a prerequisite for continuous expression of the transformed phenotype. In this study we have mapped the chromosomal location of integrated viral DNA sequences in a polyoma-induced mouse salivary gland adenocarcinoma By in situ hybridization, a major integration site was assigned t o chromosome 14, band B. The combined results from in situ hybridizations t o metaphase chromosomes, primary tumors, and cultured tumor cells indicate the presence of both integrated and free polyoma viral DNA in the tumors. Cytogenetically, the tumors were characterized by a pronounced karyotypic instability. No abnormal cells with the same karyotype were observed in any of the tumors. Nevertheless, it was possible t o recognize a preferential pattern of chromosome variation with certain common recurrent and sporadic deviations. Clonal gains and/or losses of single chromosomes were seen in all tumors. It is concluded from these results that karyotypic instability may play an important role in the genesis and progression of polyoma virus-induced salivary gland tumors.

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Section: Discussionsupporting

confidence: 93%

Karyotypic instability and viral integration in polyoma virus‐induced mouse salivary gland tumors

Sandros

Stenman

1990

Genes Chromosomes & Cancer

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“…DNA analysis. Total cellular DNA was isolated from infected or transformed cells as described previously (12,21). For gel electrophoresis, each sample containing 10 to 20 ,ug of DNA was digested with the restriction enzymes indicated below and in the figure legends.…”

Section: Methodsmentioning

confidence: 99%

Low probability of double integration in transformation of nonpermissive cells by polyomavirus

Amalfitano

Friderici

et al. 1990

J Virol

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The fate of polyomavirus genomes in stable transformants was examined in experiments in which rat or hamster cells were infected with mixed viral populations containing either two distinguishable wild types or a wild type plus a transformation-deficient mutant. The results demonstrate that in 90% of the cases in either situation, a single polyomavirus parental genome became integrated into the host genome. Both parents in the mixed infection were present in the same cells and both persisted in the infected cells until transformants appeared, eliminating the possibility that one virus would exclude the other in the early steps of the infection process. We believe that these results can be generalized to transformation events derived from normal single infections. Thus, contrary to previous results for the number of integration sites determined by restriction endonuclease and blot hybridization analysis, it appears that the probability for more than one integration event in transformation by polyomavirus is low (1 in 10). A reinterpretation of previous data is proposed.

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“…Because of the predominance of the nonrecombinant sequences, Chia and Rigby inferred (but did not confirm) that the vast majority of the transformants recovered from such mixed infections would be nonrecombinant, and they proposed that the mechanism by which integrated tandems are formed is DNA replication of a rolling-circle type. In the case of polyoma- (11,15), it is safe to conclude that at least a fraction of the integrated tandems must owe their origin to recombination. Preliminary analysis from cloned integration sites suggests that this is the case.…”

Section: Methodsmentioning

confidence: 99%

“…Models to explain the tandem topology of integrated viral genomes have invoked a role for either replication (e.g., rolling-circle type) (7,8) or recombination (11,15). Basilico and collaborators have shown that the large-T-antigen function (9) and the viral origin of replication (8) are required for tandem formation, consistent with a role for viral DNA replication.…”

mentioning

confidence: 98%

“…Previous results from our laboratory based on studies of transformants derived from mixed infections, have suggested that two parental genomes can cointegrate during the integration process (11,15). To directly analyze and quantitate the role of intervirus recombination in the process of integration-transformation of the polyomavirus genome in nonpermissive cells, we performed mixed infections with a pair of mutants which lack restriction endonuclease sites and followed the generation of recombinant wild-type restriction fragments in the population of cells early after infection as well as in the transformed cells derived from this population.…”

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confidence: 99%

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High-level recombination specific to polyomavirus genomes targeted to the integration-transformation pathway.

Hacker¹,

Fluck²

1989

Mol. Cell. Biol.

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An unusually high incidence of interviral recombination was found in the process of integration of the polyomavirus genome concomitant with neoplastic transformation of nonpermissive cells. Transformants were isolated after mixed infections of Fischer rat cells with two mutants lacking restriction endonuclease sites and were analyzed for the presence of unselected integrated recombinant restriction fragments. A large fraction of the transformants isolated (38% of the 64 transformed cel lines studied) contained recombinant viral genomes that had undergone recombination in a 1.3-, 1.7-, or 3.6-kilobase-pair interval. More than 90% of these recombinant transformants showed evidence of crossovers in multiple intervals. To our knowledge, the recombination frequencies observed in these experiments represent the highest frequencies of homologous recombination reported for a mitotic mammalian system that does not involve transfection. In contrast to the elevated level of recombination in the integrated viral genomes, no evidence of recombination was obtained among the replicated unintegrated pool of viral genomes isolated from the same population of infetted cells from which the recombinant transformants were derived. Either of two hypotheses can provide an explanation for the segregated recombination: either recombination occurs at elevated levels in a small, recombinationprone fraction of the population destined to become transformed, or recombination occurs only among those viral genomes which are engaged in the process of integration and thus interact with a recombinogenic host machinery (for example, the host scaffold). We favor the latter hypothesis.During the events leading to neoplastic transformation of nonpermissive cells by polyomavirus and simian virus (SV40), the viral genome becomes integrated into the host DNA by a mechanism that is facilitated by a viral protein, large T antigen (9, 24). Usually, the integrated viral DNA is present in head-to-tail tandem copies of the viral genome (1, 2, 4), and integration can occur at multiple sites in the genome of the transformed cell (1, 4). Integration occurs by nonhomologous recombination with host DNA and is apparently random with respect to both viral and host sequences (2, 4). At the virus-host junctions, homologies of 2 to 5 base pairs (bp) have been found (5,19,25). Rearrangements and deletions of host DNA are usually associated with the integration events (26,28).Models to explain the tandem topology of integrated viral genomes have invoked a role for either replication (e.g., rolling-circle type) (7, 8) or recombination (11, 15). Basilico and collaborators have shown that the large-T-antigen function (9) and the viral origin of replication (8) are required for tandem formation, consistent with a role for viral DNA replication. A replication step has also been postulated for SV40 by Chia and Rigby (7), based on the existence of unintegrated high-molecular-weight species of viral DNA, which were assumed to represent the unintegrated precursors of the transfor...

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Recombination induces tandem repeats of integrated viral sequences in polyoma-transformed cells

Cited by 13 publications

References 14 publications

Karyotypic instability and viral integration in polyoma virus‐induced mouse salivary gland tumors

Karyotypic instability and viral integration in polyoma virus‐induced mouse salivary gland tumors

Low probability of double integration in transformation of nonpermissive cells by polyomavirus

High-level recombination specific to polyomavirus genomes targeted to the integration-transformation pathway.

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