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EDRI Federal Project Inventory:
28868-15 Carcinogen Activation and Screening Variant Cells
- Sponsor Organization: NIH/NCI
- Project Title: 28868-15 CARCINOGEN ACTIVATION AND SCREENING VARIANT CELLS
- Project Focus: HUMAN HEALTH EFFECTS
- Description: The Ah receptor is a soluble protein complex of about 280 kD. The
receptor binds, and mediates carcinogenesis by,polycyclic aromatic
hydrocarbons (PAHs), which are found in cigarette smoke and smog,
heterocyclic amines, whichconstitute the principal carcinogens in
cooked meat, and chlorinated aromatic compounds, such as, 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD). The Ah receptor translocates from
the cytoplasm to the nucleus on binding ligand. The best understood
activity of the receptor concerns its role in the induction of
cytochrome P450IA1. Induction occursas the result of binding of the
Ah receptor-ligand complex to xenobiotic responsive transcriptional
enhancer elements(XREs) located in the upstream region of the P450IAl
gene. The Ah receptor nuclear translocator protein, Arnt, isrequired
for the Ah receptor to translocate to the nucleus; is a structural
component of the nuclear form of the Ahreceptor; and most probably
also forms part of the complex (also containing the ligand-binding
subunit of the Ahreceptor) that binds and activates the XRE.
Experiments will investigate whether Arnt i) is also a structural
componentof the cytosolic form of the Ah receptor, ii) itself
translocates to the nucleus after the Ah receptor binds ligand, iii)
bindsthe XRE directly, or indirectly via its association with the
ligand-binding subunit, and iv) if it binds directly, to
whichnucleotides in the XRE Arnt and the ligand-binding subunit each
bind. An experiment will be performed to ascertainwhether Arnt binds
to other proteins, besides the ligand-binding subunit of the Ah
receptor. The protein-bindingcapacity of Arnt will be utilized to
clone cDNAs for those proteins that interact with Arnt, including the
ligand-bindingsubunit. The role of these proteins in Ah receptor
action will be investigated by inhibiting protein activity,
usingantisense oligonucleotides or antisense cDNAs. In vitro
mutagenesis experiments will be performed on Arnt in order toidentify
putative functional domains, including domains for nuclear
translocation, for binding the ligand-binding subunit,for binding the
XRE, and for transcriptional activation. The amt gene mutations in
the two C- mutants of Hepa-1 cellswill be sought in order to confirm
that the putative mutations responsible for loss of Ah receptor
translocation in thesemutants reside in the amt gene. The promoter
region of the human amt gene will be cloned and sequenced, in order
toidentify potential regulatory effectors of the amt gene, and to
provide the means for identifying the start site oftranscription.
- References:
- Category: MODELS
- Subcategory: BASIC RESEARCH
- Keywords for Experimental System/Species: IN VITRO, HUMAN, LABORATORY STUDY
- Keywords for Experimental Endpoints: CARCINOGENESIS, XENOBIOTIC METABOLISM, CYTOCHROME P450, AH RECEPTOR,
- Chemical Agents: TCDD
- Performing Institution: UNIVERSITY OF CALIFORNIA LOS ANGELES
- Contact: CONTRACT PERSON: ELAINE C. LEE; BUILDING 31; 11A21; NATIONAL CANCER
INSTITUTE, NIH,BETHESDA, MD 20892-2590; 301-496-5515;
LEEE@OD.NCI.NIH.GOV
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