Selective Integration of Rous Sarcoma Virus Genome in High- and Low-Metastatic Transformed Cell Lines

Abstract

Previously, different hamster cell lines transformed in vitro by Rous sarcoma virus (RSV) (SR-D strain) were established [1]. These cells displayed different levels of spontaneous metastatic activity in syngenic animals. The structure of RSV provirus in these cells has been analyzed. All cell lines contained integrated RSV genome without any indication of provirus rearrangement. The comparative analysis of restriction maps of the integrated provirus in the genomes of these cells showed that in most of the highly metastatic cell lines the exogenous RSV proviruses were localized within structurally similar loci of host DNA. For the analysis and sequencing of the flanking region downstream from the integrated provirus, the method of inverted polymerase chain reaction (PCR) with oligonucleotide primers to certain long terminal repeats (LTR) and src regions of RSV was used. We analyzed the primary structure of cellular DNA for a number of different highly metastatic cell lines. It was found that the flanking sequences of cellular DNA are similar in at least three cell lines. This common fragment was used as a probe for the analysis of normal DNA and a unique region in the hamster genome was found. Homologous sequences have been also identified in the human genome. Computer sequence analysis did not show any consistent homology of this locus with any known genes.