Structure of the Mouse Cytochrome P1‐450 Genomic Gene

Abstract

Clone 46 was previously shown to represent mouse cytochrome P₁‐450 cDNA by both translation arrest experiments and segregation of induced P₁‐450 mRNA with induced aryl hydrocarbon hydroxylase activity among individual 3‐methylcholanthrene‐treated offspring of the (C57BL/6N)(DBA/2N)F₁× DBA/2N backcross. With clone 46 as a probe, a MOPC 41 mouse genomic‐DNA library was screened. λ3NT12, a 16 × 10³‐base‐pair insert of genomic DNA grown in a recombinant Charon 4A λ vector phage, was isolated and characterized. It was determined that clone 46 hybridizes to the extreme 5′ end of λ3NT12. pMJE12, a 3.0 × 10³‐base‐pair fragment in the 5′ region of λ3NT12, was subcloned in plasmid pBR322 and used as a probe to screen again the same mouse‐DNA library; recombinant phages λ3NT13, and λ3NT14, and λAhP‐1 were isolated and characterized. The relative orientation of each of the four genomic clones on the mouse chromosome was determined. Only λAhP‐1 contains the entire P₁‐450 genomic gene, which by R‐loop analysis spans about 46 × 10² base pairs and contains at least five exons. Clone 46 is shown to be a 3′ unique sequence of the genomic P₁‐450 gene. The λAhP‐1 genomic‐DNA clone from the MOPC 41 plasmocytoma is shown by a series of restriction enzymes to be the same as genomic DNA from normal mouse liver. With a subclone in the 5′ portion of the P₁‐450 gene, two and three hybridizable fragments are found with mouse genomic DNA that has been digested with EcoRI and BamHI, respectively.