Comparison of human mouse P1450 upstream regulatory sequences in liver- and nonliver-derived cell lines

The foreign chemical tetrachlorodibenzo-p-dioxin (TCDD) is known to interact with the aromatic hydrocarbon receptor and, in turn, activate transcription of the mouse P1450 and P3450 genes. Various lengths of DNA upstream from the human P1450 gene were inserted into the promoterless pSVO-cat prokaryotic expression vector and compared with mouse P1450 upstream sequences similarly treated. The constructs were cotransfected with pSV2-neo into human, mouse, and monkey liver- and nonliver-derived cell lines. After selection in G418, the transformed colonies were treated with control medium, TCDD, or, in some cases, cycloheximide. Pooled transformants were then assayed for chloramphenicol acetyltransferase activity. The data are consistent with the presence of several functional regulatory regions within the upstream DNA: a promoter region, a region that is negatively autoregulated, and a region further upstream that activates transcription and is dependent upon a functional aromatic hydrocarbon receptor. Compared with 1604 base pairs of human P1450 upstream sequences, 1646 base pairs of mouse P1450 upstream sequences exhibit an increased sensitivity to TCDD; this effect was found to require both trans-acting protein factors and cis-acting DNA elements. Our results demonstrate the successful interaction of mouse trans-acting factors with human P1450 upstream sequences and human trans-acting factors with mouse P1450 upstream sequences.