English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Fischer rat fibroblasts transformed by polyoma virus contain, in addition to viral sequences integrated into the host genome, nonintegrated viral DNA molecules, whose presence is under the control of the viral A gene. To understand the mechanism of production of the "free" viral DNA, we have characterized the DNA species produced by several rat lines transformed by wild-type virus or by ts-a polyoma virus and compared them with the integrated viral sequences. Every cell line tested yielded a characteristic number of discrete species of viral DNA. The presence of defectives was a very common occurrence, and these molecules generally carried deletions mapping in the viral "late" region. The production of multiple species of free viral DNA was not due to heterogeneity of the transformed rat cell population, and its pattern did not change upon fusion with permissive mouse cells. Analysis of the integrated viral DNA sequences in the same cell lines showed, in most cases, a full head-to-tail tandem arrangement of normal-size and defective molecules. The free DNA produced by these lines faithfully reflected the integrated species. This was true also in the case of a cell line which contained a viral insertion corresponding to approximately 1.3 polyoma genomes, with each of the repeated portions of the viral DNA molecule carrying a different-size deletion. These results support the hypothesis that the free DNA derives from the integrated form through a mechanism of homologous recombination leading to excision and limited replication.

Relationship between integrated and nonintegrated viral DNA in rat cells transformed by polyoma virus