CELL‐LINE SPECIFIC ACTIVATION OF SV40 TRANSCRIPTIONAL ENHANCER BY p40(tax) OF HTLV‐1

A transcriptional trans‐activator P40(tax) of HTLV‐1 was reported to activate HTLV‐1 enhancer, but not SV40 or Rous sarcoma virus enhancer. However, in certain cell lines, we found that SV40 enhancer was activated by p40(tax). These cell lines were mostly T cells, where the SV40 enhancer showed only low activity without p40(tax). Since p40(tax)‐mediated activation of the LTR is not cell line‐specific, the activation of enhancers by p40(tax) depends on the combination of enhancer and cell type used for the test. Thus, apparent activation by p40(tax) depends on variable cellular components involved in transcriptional regulation.