ABSTRACT
Clones and subclones of Schmidt-Ruppin-RSV-D-(SRD-) infected rat cells that were isolated in soft agar have shown differences in their morphology. Some of the subclones were round or spindle-shaped cells with lower anchorage dependence and high growth rate, while others were more fibroblast-like and failed to overgrow one another. In correlation to their morphology, subclones with high degree of phenotypic transformation contained amplified amounts of full length proviral DNA or proviral fragments. The amplification affected the proviral DNA elements together with host cellular DNA sequences. We have also shown a relationship between the copy number of the proviruses in the cells, the level of expression of viral RNA, and between those two parameters and the various degrees of phenotypic transformation.