Aryl Hydrocarbon (Ah) Receptor Gene Expression

Original article


I.M. Ateitalla 1, S. Brown 2

1-Biochemistry Department, Faculty of Medicine, Garyounis University, Benghazi, Libya. 2-Department of Biochemistry, Medical School, Nottingham University, Nottingham, UK.

Garyounis Medical Journal Vol.20,No.1.2003:79-88


Objectives: A gene had been identified as being necessary for the induced activity of aryl hydrocarbon hydroxylase(AHH) in human cells. This enzyme, which contains the cytochrome P4501 A1, is the primary activation enzyme responsible for the metabolism of carcinogens such as benzo[a]pyrene. Its level of activity has been associated with the risk of lung cancer in cigarette smokers. A gene necessary for AHH activity in hybrid cells had previously been located on human chromosome 2. The nature of this gene was unclear when the structural gene for cytochrome P4501A1 was subsequently located on human chromosome 15. RAG cells were known not to express any detectable levels of basal or inducible AHH activity. Aim: It was decided to test whether the gene on human chromosome 2 could be the Ah receptor gene which is necessary for the induced AHH activity in cells. It was also decided to test mouse RAG cells for the mouse Ah receptor gene and its activity. Materials & Methods: Primers were designed which could detect the human receptor gene in human x mouse hybrids and a number of clones were examined. RAG cell mRNA was isolated and the combination of reverse transcription and PCR was then used to test for expression of the gene in induced and uninduced RAG cells. Results: Correlation of the segregation of the receptor gene with human chromosome markers did show that it segregated with human chromosome 2. Moreover, when a different set of hybrid cells were tested it was found that in a primary hybrid clone containing the complete human chromosome 2 the receptor gene was present but a hybrid subclone which had previously been shown to lack the p terminus of human chromosome 2 lacked the Ah receptor gene. Conclusion: we can conclude that the Ah receptor gene is located at the p terminus of human chromosome 2. It has also been shown that there is a low level of expression in RAG cells with and without induction.

Keywords: Aryl hydrocarbon receptor, PCR, Benzo[a] pyrene, A549 cells, RAG cells.