CYTOCHROME P-450 GENE STRUCTURE AND REGULATION

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The PAH-inducible P-450 are responsible for the metabolism of carcinogens, as well aS a wide variety of both endogenous and exogenous compounds. The metabolism of these compounds can occur via pathways that contribute to their detoxification, or via pathways that activate them to highly cArcinogenic forms. It is thought that the balance between detoxification and activation is crucial to the process of chemicAl carcinogenesis and that differences between individuals in the expression of specific P- 450 enzymatic activities may substantially influence this balance. This will, in turn, influence the susceptibility of the individual to specific forms of cancer. The source of this difference in enzymatic activities could reside in either the structural gene encoding P-450 enzymes or in the regulatory genes that control the expression of specific members of the P-450 gene family. In-depth knowledge regarding the structure and regulation of the P-450 structural genes and regulatory genes is required to determine the actual importance of these genes and their gene products in determining cancer susceptibility. The objective of this research program is to provide this basic information. The specific objectives are as follows: 1. A manifold of cis-acting sequences respond to different trans- acting factors to control the transcription of the P-450c, and probably, P-450d genes. We will use DNA-mediated gene transfer to characterized cis-acting transcriptional regulatory sequences, and mapping techniques to identify and characterize the DNA binding proteins (probably regulatory in function) that interact with these sequences. We will purify selected DNA binding proteins, characterize them biochemically, clone cDNAs corresponding to the mRNAs encoding these factors and study the regulation of these mRNAs. 2. Multiple post-transcription regulatory mechanisms controlling P-450c and P-450d mRNA levels will be studied: the structures of P-450 mRNAs, mRNA precursors and mRNA degradation products will be analyzed; mRNA sequences controlling post-transcriptional events will be located by DNA-mediated gene transfer experiments; an proteins that mediate post-transcriptional processes will be studied biochemically. 3. Accomplishing the above objectives will develop molecular- genetic tools that will be useful for assessing the role of the P- 450s in carcinogenesis and also, for determining the molecular basis of the variations among individuals in their susceptibility to specific forms of cancer.