Long terminal repeat enhancement of v-mos transforming activity: identification of essential regions.

The transforming efficiency of recombinant DNA clones containing the Moloney sarcoma virus v-mos sequence was enhanced by introducing the Moloney sarcoma virus long terminal repeat (LTR) in either the 5' or 3' position relative to v-mos. We analyzed the polyadenylated RNA expressed in cells transformed by these recombinant DNA clones and examined the structural integrity of integrated copies of the DNA. In each case, we demonstrated the presence of v-mos containing RNA transcripts in the polyadenylated RNA and showed that these RNA transcripts are consistent with the structure of the transfected DNA. The analysis of DNA from these transformed cells showed that the relative positions of the v-mos and LTR sequences within the transfected DNA were conserved in the integrated DNA copies. These results demonstrate that a single LTR can successfully enhance the transforming activity of v-mos from either a 5' or a 3' relative position. The results from the transfection analysis of recombinant clones containing only portions of the LTR introduced 3' to v-mos demonstrate that the essential region of the LTR responsible for the enhancement of transformation is a region within the unique 3' sequences of the LTR containing the 73-base-pair tandem repeat sequence.