Comparison of the mouse P(1)450 gene and flanking sequences from a MOPC 41 plasmacytoma and normal liver.

The murine P(1)450 gene is inducible by foreign chemicals such as dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD). The induction process appears to involve binding of TCDD to the Ah receptor, interaction of the inducer-receptor complex with chromatin, and transcriptional activation of the P(1)450 gene. P(1)450 gene expression did not occur in the MOPC 41 plasmacytoma transplanted intra-abdominally in the BALB/c mouse. By Southern blot analysis, the P(1)450 gene restriction patterns are similar between MOPC 41 DNA and normal mouse liver DNA digested with Eco RI, Bam HI, or Hind III, suggesting there is no evidence for a gross chromosomal rearrangement in the tumor P(1)450 gene. The P(1)450 gene isolated from a genomic DNA library derived from the MOPC 41 tumor lacked the first exon and two-thirds of the first intron because of a rearrangement that presumably occurred during construction of the genomic DNA library. An unknown upstream segment of 2578 bases that had recombined with the remainder of the P(1)450 gene was sequenced and found to contain several repetitive sequences on both strands. The remaining 6272 bases of the P(1)450 gene (2532 bp of exons, 1969 bp of introns and 1771 bp of 3'-flanking region) are identical between the BALB/cJ-derived MOPC 41 and normal C57BL/6N mouse liver, with the exception of one CTTT repeat in the second intron. Hence, the BALB/c and C57BL/6 inbred mice, generally regarded as among the most divergent of Mus domesticus inbred laboratory strains, possess a P(1)450 gene and flanking region that exhibit greater than 99.9% similarity in nucleotide sequence.