[Amplification of virocellular sequences avian adenovirus-induced tumor cells]

Adenovirus-induced tumor cells (including transformed cells) examined contain a part of the viral genome. However, number of molecules of the virus DNA persisting in a cell varies in the tumor cell lines. Tumor cell lines which were induced by CELO virus, an avian adenovirus, carried the virus DNA in the range from 1 to 920 molecules Per cell. Of the tumor cell line which carried large numbers of molecules of the virus DNR, one tumor cell line, RT 13 (160 molecules/cell), was studied both at the molecular level using DNA cloning and southern blot hybridization and at the cytological level using in situ hybridization, in order to elucidate the mode of existence of virus DNA and to reveal how such mode of existence emerged. This study indicated the followings: During the course of tumorigenesis, the virus DNA sequence (14.1 kilo base pairs) together with flanking cellular sequences formed "amplification" unit, and the unit was amplified about 160 times. The amplified cellular DNA sequences flanking to the left and right termini of the virus DNA sequence were longer than 6.8 and 16.3 kilo base pairs, respectively. Most of these amplified DNA sequences were localized in the limited region of specific chromosome (s). Possible effect of the amplification of virus DNA sequence on malignant cell transformation is discussed in the text, being referred to the amplification of cellular onc-genes reported recently.