Alternative splicing of CYP2D mRNA in human breast tissue.
The human cytochrome P450 (CYP) 2D subfamily comprises the CYP2D6 gene and four pseudogenes, CYP2D7P1 and 2 and CYP2D8P1 and 2. The CYP2D6 gene product is a prominent drug-metabolizing enzyme, which is probably constitutive and has no known inducing agents. Alternative splicing of the pre-mRNAs of these genes has been detected in human liver and breast tissue. RNA-PCR, competitive RNA-PCR, Southern blotting, cDNA sequencing, and gene-specific PCR have been used to fully characterize the alternatively spliced forms of CYP2D mRNA in human breast tissue in the region of exon 5 to 8. Such alternative splicing could regulate the expression of CYP2D6 protein. A full-length mRNA (exons 5 to 8), and variants c (exon 6 deleted), b' (3' portion of exon 6 deleted), e (3' portion of exon 6 deleted, 3' 57-bp portion of intron 6 included), d (3' 57-bp portion of intron 6 included), and b (intron 6 included) were characterized and quantitated. Variant c was derived from CYP2D6, variants d, e, and b were from CYP2D7P, and variant b' and full-length mRNA were derived from both CYP2D6 and 2D7P. Full-length mRNA was a minor form in human breast tissue where variants b' and c predominated. Human breast tumor MCF-7 cells had CYP2D mRNA splice variant patterns similar to those of human breast tissue, while human liver tumor HepG2 cells had wild-type mRNA predominating. These results suggest that CYP2D6 could be regulated tissue specifically using tissue-specific alternative mRNA splicing.
Huang
Z
Z
Department of Environmental Health and Toxicology, University at Albany, State University of New York 12201, USA.
Fasco
M J
MJ
Kaminsky
L S
LS
D017398:Alternative Splicing; D001483:Base Sequence; D001940:Breast / Q000201:enzymology*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D018076:DNA, Complementary; D006801:Humans; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics*; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System