A human gene, encoding a protein highly homologous to CYP2A7, has been isolated. Only thirteen base pair differences resulting in five amino acid changes were found. Genomic analysis demonstrated that the isolated gene is an allele of <I>CYP2A7</I>, designated <I>CYP2A7A</I>. The gene is about 8 kb long and contains 9 exons encoding a protein of 494 amino acids. The 0.5 kb 5' flanking region of <I>CYP2A7A</I> contained several putative promoter elements including a typical TATA box, a steroid regulatory element (SRE), and a HepG2-specific factor-1 binding sequence (HPF-1). The presence of HPF-1 motif was essential for the transcription of the gene in HepG2 cells. However, the function of SRE element is still unclear. In order to investigate the relationship between the expression levels of human <I>CYP2A</I> genes and the polymorphisms of coumarin hydroxylase activity in man, three cDNAs, <I>CYP2A6, CYP2A7</I> and an alternatively spliced version of <I>CYP2A7 (CYP2A7AS)</I> have been cloned. The later one was missing exon 2 but contained a 10 bp segment of intron 1. Translation of the <I>CYP2A7AS</I> resulted in an in frame deletion of 51 amino acids. The expression of these cDNA's in COS-7 cells showed that both CYP2A6 and CYP2A7 generated a protein <I>M</I>r 49 kDa, while the protein product of CYP2A7AS was about 44 kDa. Only the CYP2A6 had coumarin hydroxylase activity. The relative level of mRNA encoding CYP2A6 and CYP2A7 was established in six human liver samples with RT-PCR followed by PstI digestion and found to range between 1:0.5 to 1:3, respectively. These results showed that the relative level of CYP2A7 was variable.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649560 |
| Date | January 1995 |
| Creators | Ding, Shaohong |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/20936 |
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