Ras oncogenes and p53 suppressor genes in fish carcinogenesis models Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/ns064864z

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  • A digoxigenin-labeled nonradioactive detection system was used to screen a zebrafish cDNA library for p53-like and ras-like genes. One clone was isolated and identified as an incomplete p53-like gene. The insert size of this clone is 1777 bp, which encodes part of evolutionarily conserved region II and all of regions III, IV, and V. A magnetically enriched whole zebrafish cDNA library was constructed to enhance possible recovery of ras-like genes in zebrafish. One clone, termed Zras-Bl, carried an insert of 2592 bp with an open reading frame encoding a 188 amino acid residue ras p21 protein. Based on total protein sequence, this expressed zebrafish ras p21 is most closely related to human N-ras (91% homology), with lesser homology to Ha-ras (84%) and Ki-ras (85%). Preliminary partial sequence data obtained by genomic and reverase transcriptasepolymerase chain reaction (RT-PCR) screening indicate the presence of at least one additional expressed ras gene in zebrafish. The tumorigenicity and Ki-ras mutational properties of dietary 7,12-dimethylbenz[a]anthracene (DMBA) and dibenzo[a,l]pyrene (DBP) were compared in rainbow trout. Both chemicals elicited predominantly 12(1)G->A and 12(2)G->T mutations in trout liver tumors. Two {12(1)G->T and 12(2)G->T} and one {12(1)G->A and 12(2)G->T} double mutation were also observed in DBP livers tumors, but not in DMBA liver tumors. Some stomach tumors from both chemicals exhibited so much DNA degradation that routine PCR amplification was not possible. Among sixteen DMBA stomach tumors with intact DNA, no Ki-ras mutations were found. Of sixteen DBP stomach tumors examined, one had 12(1)G->A and two had 13(1)G->C mutations. The observed G->T transversions are compatible with apurinic mutagenesis driven by unstable DNA adducts arising from one-electron oxidation, but this is not true for the major G->A transitions or G->C transversions and rare double mutations found in this study. The low sensitivity of direct sequencing may limit the frequency of ras mutant detection in this study.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-01-03T21:32:47Z (GMT) No. of bitstreams: 1 CHENGRONSHAN1995.pdf: 1784634 bytes, checksum: 4a23272d1bdee2c9e253331f5e53416a (MD5)
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-01-26T19:42:11Z (GMT) No. of bitstreams: 1 CHENGRONSHAN1995.pdf: 1784634 bytes, checksum: 4a23272d1bdee2c9e253331f5e53416a (MD5)
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