Low molecular weight RNAs with homologies to cellular DNA at sites of adenovirus DNA insertion in hamster or mouse cells.

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Abstract
The adenovirus type 2 (Ad2)-transformed hamster cell line HE5 contains one or very few integrated copies of Ad2 DNA. At the site of insertion of Ad2 DNA, the cellular DNA sequence was completely preserved and has homologies to small unpolyadenylated, cytoplasmic RNA of 300 nucleotides in length and to minority populations of smaller RNA present in HE5 cells and in normal hamster cells. The 300-nucleotide RNA is present on average in .apprx. 20 copies/cell. This RNA, and shorter RNA, reveal homologies to the hamster DNA sequence of .apprx. 400 nucleotides to the right of the site of insertion of Ad2 DNA, which is present in one or very few copies per genome. The nucleotide sequence of the DNA segment homologous to this RNA does not contain open reading frames in excess of a sequence encoding 18 amino acids. The small RNA are probably not actually translated and their function is unknown. The nucleotide sequence does not exhibit similarities to known low MW RNA of eukaryotic origin. The low MW cellular RNA was found in HE5 cells, in other hamster cell lines and organs, and also in mouse cells. There are differences with respect to size and abundance in the RNA smaller than 300 nucleotides between HE5 cells and LSH hamster embryo cells. The adenovirus type 12 (Ad12)-induced mouse tumor CBA-12-1-T carries > 30 copies of integrated Ad12 DNA. The cellular DNA sequence at the site of Ad12 DNA insertion exhibits homologies to small RNA (.apprx. 300 nucleotides long) from mouse cells. The finding of low MW RNA with homologies to cellular DNA at the site of insertion of adenovirus DNA suggests that foreign DNA can perhaps be more easily inserted at cellular sites which are actively transcribed.