The Rous sarcoma virus long terminal repeat is a strong promoter when introduced into a variety of eukaryotic cells by DNA-mediated transfection.

Abstract

The transcriptional activity of the long terminal repeat (LTR) of Rous sarcoma virus was characterized by constructing a recombinant plasmid, pRSVcat, in which bacterial chloramphenicol acetyltransferase (CAT; acetyl-CoA:chloramphenicol 3-O-acetyltransferase, EC 2.3.1.28) coding sequences are placed under LTR control. The LTR directs relatively high levels of CAT synthesis within 48 h after calcium phosphate-mediated introduction of this plasmid into CV-1 monkey kidney cells, chicken embryo fibroblasts, Chinese hamster ovary cells, human cervical carcinoma HeLa cells or mouse NIH/3T3 cells. The level of CAT synthesis is 3-fold higher in CV-1 cells and up to 10-fold higher in HeLa and mouse NIH/3T3 cells than after transfection with a related vector, pSV2cat, carrying CAT sequences under control of the SV 40 early promoter. By primer extension, the amounts of CAT-specific mRNA encoded by pRSVcat and pSVcat were shown to correlate with the levels of CAT enzyme activity. By both S1 nuclease mapping and primer extension, the start site for RNA transcription within the LTR of pRSV cat was demonstrated to correspond to previous mapping data. Transfection efficiencies were estimated by monitoring immunofluorescence induced by a rhodamine-labeled CAT antibody. Evidently, the Rous sarcoma virus LTR can direct synthesis of high levels of functional mRNA and has a wide expression range. The observed high transcriptional activity of the LTR is significant because it has been postulated that this LTR promotes activity of adjacent cellular oncogenes.