J. Biol. Chem., Vol. 263, Issue 2, 701-707, Jan, 1988
Complementary DNA cloning of cytochrome P-450s related to P-450(M-1) from the complementary DNA library of female rat livers. Predicted primary structures for P-450f, PB-1, and PB-1-related protein with a bizarre replacement block and their mode of transcriptional expression
H Kimura, H Yoshioka, K Sogawa, Y Sakai and Y Fujii-Kuriyama
Department of Biochemistry, Japanese Foundation for Cancer Research, Tokyo.
Three kinds of cDNA clones were isolated from a cDNA library synthesized
from female rat liver mRNA by cross-hybridization with the P-450(M-1) cDNA
as a probe and sequenced. One clone appears to be the previously isolated
P-450f cDNA clone with an additional 5'- untranslated and coding sequence
which are lacking in the previously reported clone (Gonzalez, F. J.,
Kimura, S., Song, B.-J., Pastewka, J., Gelboin, H. V., and Hardwick, J. P.
(1986) J. Biol. Chem. 261, 10667- 10672), though several nucleotide
differences were seen. Another one is for P-450PB-1 mRNA previously
isolated, and the last has an almost identical nucleotide sequence to
P-450PB-1 (the same report cited above) except for one region of 159 base
pairs where the sequence homology between the two is abruptly broken down.
This nonhomologous region appears to correspond exactly to the entire
eighth exon, estimated by comparison with the gene structure of the related
P-450 (P- 450(M-1)). This replacement in P-450PB-1 (ps) causes a frameshift
in the open reading frame, resulting in the generation of a truncated form
of P-450 with a strange replacement block and lacking the heme-binding
region. This observation suggests that the mRNA whose cDNA was cloned here
was produced from a recombinant gene generated by gene conversion or from
alternative splicing of a cryptic exon. Sex- and age-dependent expression
of the mRNAs investigated by dot blot analysis revealed that normal- and
pseudo-type PB-1 mRNA were expressed in both male and female rat livers,
though their age-dependent expression was different in male and female
animals. In addition, both the mRNAs were specifically expressed in the
female brain of 8 weeks, whereas practically no expression was observed in
kidney and lung of both sexes.
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