The mechanisms underlying chemically-mediated malignant transformation are to be explored. Model systems to be used include in vivo exposure of rodents to thioacetamide, ethionine, alkylnitrosamines, and amino azo dyes. In vitro exposure of hepatocyte cultures to these same agents will also be employed. Previous data show a modification of nuclear restriction of RNA species in liver cells exposed to carcinogens, potentially representing an initiating or a promoting event, or both. The major areas to be investigated include: (1) an analysis of the cell-free model of nuclear RNA transport to determine the role of high-energy bond hydrolysis as a driving force, and to assay for the significance of both selection of RNA species for secretion and for back-diffusion to the nucleus; (2) an analysis of in vivo restriction in the two-stage model of hepatocarcinogenesis to learn whether """"""""nuclear leakage"""""""" is related to initiation or to promotion; (3) the fidelity of the in vitro system will be surveyed. Specific cDNA probes for messenger species (Alpha1-glycoprotein and AlphaMu-globulin) will be used to measure messenger release in vivo and compare these data to in vitro release following turpentine and androgenic stimulation of male rats. Additionally, these cDNA probes will be used to isolate the messengers in vivo and in vitro to compare splicing, processing, and polyadenylation following the release in vivo and in vitro; 4) an attempt wil be made to purify and characterize the nuclear matrix and nuclear envelope NTase and to define their role in transport. The potential that these also represent an ATP driven endonuclease will be tested. This point seems relevant to the apparent frequency of genetic information relocation associated with oncogene expression. These experiments will be used to test the hypothesis that malignant transformation involves alterations in the transcription and processing of RNA, at least as a basis for the phenotypic expression of cancer.
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