A novel human cytochrome P450 gene (P450IIB): chromosomal localization and evidence for alternative splicing.

We have isolated from a single human liver cDNA library two clones which are highly homologous (78% over the coding region) to the major phenobarbital-inducible P450 from rat (P450IIB1). This is the first direct demonstration of the presence of the P450IIB gene subfamily in humans. This subfamily is much less extensive than the rodent homologues, but does appear to contain at least two genes. Of the cDNA clones isolated one is apparently normally spliced, whereas the other lacks exon 8 and retains all or part of intron 5. Both clones contain transcribed Alu sequences. The human P450IIB gene has been located to chromosome 19q12----19q13.2 using a probe derived from intron 5, and is close to the CYP 2A locus encoding cytochrome P450IIA2. Restriction fragment length polymorphisms have been found with the enzymes BamHI and MspI which will enable linkage to be determined between these two loci.