Genomic organization of the human CYP3A locus: identification of a new, inducible CYP3A gene

Pharmacogenetics. 2001 Mar;11(2):111-21. doi: 10.1097/00008571-200103000-00002.


Proteins encoded by the human CYP3A genes metabolize every second drug currently in use. The activity of CYP3A gene products in the general population is highly variable and may affect the efficacy and safety of drugs metabolized by these enzymes. The mechanisms underlying this variability are poorly understood, but they include gene induction, protein inhibition and unknown genetic polymorphisms. To better understand the regulation of CYP3A expression and to provide a basis for a screen of genetic polymorphisms, we determined and analysed the sequence of the human CYP3A locus. The 231 kb locus sequence contains the three CYP3A genes described previously (CYP3A4, CYP3A5 and CYP3A7), three pseudogenes as well as a novel CYP3A gene termed CYP3A43. The gene encodes a putative protein with between 71.5% and 75.8% identity to the other CYP3A proteins. The highest expression level of CYP3A43 mRNA is observed in the prostate, an organ with extensive steroid metabolism. CYP3A43 is also expressed in several other tissues including liver, where it can be induced by rifampicin. CYP3A43 transcripts undergo extensive splicing. The identification of a new member of the CYP3A family and the characterization of the full CYP3A locus will aid efforts to identify the genetic variants underlying its variable expression. This, in turn, will lead to a better optimization of therapies involving the numerous substrates of CYP3A proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aryl Hydrocarbon Hydroxylases*
  • Base Sequence
  • Chromosome Mapping
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme System / genetics*
  • DNA Primers
  • DNA, Complementary
  • Gene Expression Regulation, Enzymologic* / drug effects
  • Hepatocytes / drug effects
  • Hepatocytes / enzymology
  • Humans
  • Molecular Sequence Data
  • Oxidoreductases, N-Demethylating / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Rifampin / pharmacology
  • Transcriptional Activation


  • DNA Primers
  • DNA, Complementary
  • Cytochrome P-450 Enzyme System
  • Aryl Hydrocarbon Hydroxylases
  • Cytochrome P-450 CYP3A
  • Oxidoreductases, N-Demethylating
  • Rifampin

Associated data

  • GENBANK/AC005020
  • GENBANK/AC011904