Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Multiple fluorescence-based PCR single-strand conformation polymorphism (MF-PCR-SSCP) with postlabeling was developed. The target sequence was amplified by PCR using unlabeled primers. Free dNTPs were removed from the amplified products by ethanol precipitation. The dNTPs at the 3' ends of the amplified DNA fragments were exchanged with fluorescent dUTPs or ddNTPs using Klenow fragment of DNA polymerase I. The DNA fragments labeled with fluorescent dUTPs or ddNTPs were heat denatured and applied to a nondenaturing polyacrylamide gel set on an automated DNA sequencer with a gel temperature-controlling system. The image data were analyzed by the computer program Genescan 672. By use of MF-PCR-SSCP with postlabeling, seven different single base mutations of the human K-ras oncogene were detected even under one electrophoresis condition.
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PMID:Multiple fluorescence-based PCR-SSCP analysis with postlabeling. 758 Sep 14

We examined the differential effects of the H-ras oncogene and the K-ras oncogene on cisplatin sensitivity in murine NIH/3T3 cells transfected with these oncogenes. Although the NIH/3T3 cells transformed with H-ras oncogenes (EJ-NIH/3T3 and Ha8-21) showed an increased resistance to cisplatin compared to the parental NIH/3T3, the cell lines transformed with K-ras oncogenes (DT and 1,8DNP2-2-5) did not. Compared with NIH/3T3, the 2 H-ras transformants reduced both the accumulation of cisplatin and the Na+,K(+)-ATPase activity in the membrane fraction. On the other hand, we observed no significant difference in cellular accumulation of cisplatin or in Na+,K(+)-ATPase activity between parental NIH/3T3 and the K-ras transformants. Since these ras transformants did not affect the cellular metallothionein content, transcriptional level of DNA polymerase beta or activity of glutathione-S-transferase which is not associated with cisplatin sensitivity, these results suggest that cisplatin resistance is brought about by the H-ras oncogene, but not by K-ras, and that induction of cisplatin resistance by H-ras is mainly due to a reduction of cisplatin accumulation and an impairment of Na+,K(+)-ATPase activity in the membrane fraction.
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PMID:Differential Na+,K(+)-ATPase activity and cisplatin sensitivity between transformants induced by H-ras and those induced by K-ras. 807 52

A retroviral vector system was developed to transduce a K-ras antisense construct efficiently into human cancer cells. A 2-kb fragment of K-ras gene DNA in antisense orientation was linked to a beta-actin promoter and inserted into retroviral vector LNSX in two different orientations. The constructs were transfected into amphotropic packaging cell line GP+envAm12 followed by alternating transduction between the ecotropic packaging cell line psi-2 and GP+envAm12. Titers up to 9.7 x 10(7) colony-forming units (cfu)/ml were achieved without detectable replication-competent virus. The human large cell lung carcinoma cell line H460a, which has a homozygous codon 61 K-ras mutation, was transduced with an efficiency of 95% after five to seven repeated transductions. DNA polymerase chain reaction (PCR) and genomic DNA Southern blot analysis showed that the retroviral construct was integrated into the genome of H460a cells. K-ras antisense RNA expression was detected in the cells by Northern analysis, slot blot hybridization, and reverse transcriptase-PCR. Translation of the mutated K-ras p21 protein RNA was specifically inhibited, whereas expression of other p21 species was unchanged. Proliferation of H460a cells was suppressed 10-fold following transduction by the antisense construct. Colony formation in soft agarose and tumorigenicity in an orthotopic lung cancer model in nu/nu mice were dramatically reduced in H460a cells expressing antisense K-ras. We conclude that an antisense construct for K-ras can be expressed effectively in a retroviral vector that can efficiently transduce human cancer cells.
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PMID:Retroviral vector-mediated transduction of K-ras antisense RNA into human lung cancer cells inhibits expression of the malignant phenotype. 839 92

In situ PCR is a new technique for the localization of low copy number sequences. We report here a method for the in situ visualization of a point mutation in K-ras codon 12 by indirect in situ PCR. Twenty-five primers were examined to select mutant-specific primers. Harvested cell lines were fixed and suspended in PCR mixture. Forty cycles of PCR in cell suspension was performed in a thermal cycler using a hot start method. Cells were cytocentrifuged onto slides, and post-fixation was performed. The specimens on the slides were then hybridized with a digoxigenin-labeled probe, followed by color reaction. Both Calu-1 (mutated: TGT) and NCI-H460 (wild type: GGT) cells had strong hybridization signals in the nuclei with general primers. But with mutant-specific primers, only Calu-1 cells had hybridization signals. No signal was observed without primers or Taq DNA polymerase. Southern blotting of the same preparation confirmed desired amplification. We also applied direct in situ PCR, but this method failed to detect the point mutation. We conclude that our indirect in situ PCR method shows the feasibility of in situ identification of single cells carrying point mutations.
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PMID:Detection of K-ras point mutation by in situ PCR in cell suspensions: comparison of the indirect and direct methods. 923 54

The long-term treatment of tamoxifen (TAM), widely used for adjuvant chemotherapy and chemoprevention for breast cancer, increases a risk of developing endometrial cancer. A high frequency of K-ras mutations has been observed in the endometrium of women treated with TAM. Human DNA polymerase (pol) eta and pol kappa are highly expressed in the reproductive organs and are associated with translesion synthesis past bulky DNA adducts. To explore the miscoding properties of alpha-(N2-deoxyguanosinyl)tamoxifen (dG-N2-TAM), a major TAM-DNA adduct, site-specifically modified oligodeoxynucleotides containing a single diastereoisomer of trans or cis forms of dG-N2-TAM were prepared by phosphoramidite chemical procedure and used as templates. The primer extension reaction catalyzed by pol kappa deltaC, a truncated form of pol kappa, extended more efficiently past the adduct than that of pol eta by incorporating dCMP, a correct base, opposite the adduct. With pol eta, all diastereoisomers of dG-N2-TAM promoted small amounts of direct incorporation of dAMP and deletions. With pol kappa deltaC, dG-N2-TAM promoted small amounts of dTMP and/or dAMP incorporations and deletions. The miscoding properties varied depending on the diastereoisomer of dG-N2-TAM adducts and the DNA pol used. Steady-state kinetic studies were also performed using either the nonspecific sequence or the K-ras gene sequence containing a single dG-N2-TAM at the second base of codon 12. With pol eta, the bypass frequency past the dA x dG-N2-TAM pair positioned in the K-ras sequence was only 2.3 times lower than that for the dC x dG-N2-TAM pair, indicating that dG-N2-TAM in the K-ras sequence has higher miscoding potential than that in the nonspecific sequence. However, with pol kappa deltaC, the bypass frequency past the dC x dG-N2-TAM pair was higher than that of the dT x dG-N2-TAM pair in both sequences. The properties of pol eta and pol kappa are consistent with the mutagenic events attributed to TAM-DNA adducts.
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PMID:Translesion synthesis past tamoxifen-derived DNA adducts by human DNA polymerases eta and kappa. 1700 16

Sensitive detection of tumor-specific point mutations is of interest in both the early detection of cancer and the monitoring of treatment at a molecular level. Recently, peptide nucleic acid (PNA) clamp real-time PCR has provided a time-sparing and sensitive method for the detection of mutations in the presence of a large excess of wild-type DNA. We present the first report that the sensitivity of PNA clamp PCR is limited by the low fidelity of TaqDNA polymerase. Replication errors introduced by Taq polymerase in the PNA-binding site were amplified during PCR due to the resulting mismatches between PNA and DNA. To reduce the frequency of polymerase-induced errors, we developed a PNA clamp PCR assay for the detection of mutations in codons 12 and 13 of the K-ras gene based on a high-fidelity DNA polymerase. The sensitivity of our assay increased approximately 10-fold, significantly detecting mutant DNA diluted 20,000-fold in wild-type DNA (P = 0.025), compared with its detection at 2000-fold dilution (P = 0.039) when Taq polymerase was used. Our data suggest that the replication errors caused by Taq polymerase must be taken into consideration for PNA clamp PCR and for other methods based on selective PCR amplification, and that these assays can be enhanced by high-fidelity DNA polymerases.
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PMID:High-fidelity DNA polymerase enhances the sensitivity of a peptide nucleic acid clamp PCR assay for K-ras mutations. 1855 64

In order to investigate the relationship between a potential defect in the DNA repair system and human lung carcinogenesis, we examined the entire coding region of the human DNA polymerase beta gene using the reverse transcription-polymerase chain reaction (RT-PCR)/single-strand conformation polymorphism (SSCP) method in 31 human lung carcinoma cell lines (18 non-small cell lung carcinoma (NSCLC) cell lines and 13 small cell lung carcinoma (SCLC) cell lines, 4 cell lines with K-ras point mutation, 9 with p53 point mutation, 3 with retinoblastoma susceptibility (Rb) gene alteration). Mutation of the polymerase beta gene was undetectable in all of them. These results suggest that mutations of the DNA polymerae beta gene is extremely rare if it occurs at all in human lung cancer, and may have no relation with K-ras, p53, or Rb gene alterations.
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PMID:No occurrence of DNA-polymerase Beta-gene mutation in human lung-carcinoma cell-lines with k-ras as, p53, or rb gene alterations. 2159 10

Inherited as well as acquired deficiencies in specific DNA mismatch repair (MMR) components are associated with the development of a wide range of benign and malignant neoplasms. Loss of key members such as MSH2 and MLH1 severely cripples the ability of the cell to recognize and correct such lesions as base:base mismatches and replicative DNA polymerase errors such as slippages at repetitive sequences. Genomic instability resulting from MMR deficiency not only predisposes cells to malignant transformation but may also promote tumor progression. To test the latter, we interbred Msh2(-/-) mice with the K-ras(LA1/+) transgenic line that spontaneously develops a range of premalignant and malignant lung lesions. Compared to K-ras(LA1/+) mice, K-ras(LA1/+); Msh2(-/-) mice developed lung adenomas and adenocarcinomas at an increased frequency and also demonstrated evidence of accelerated adenocarcinoma growth. Since MMR defects have been identified in some human lung cancers, the mutant mice may not only be of preclinical utility but they will also be useful in identifying gene alterations able to act in concert with Kras mutants to promote tumor progression.
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PMID:DNA mismatch repair deficiency accelerates lung neoplasm development in K-ras(LA1/+) mice: a brief report. 2577 71