Selective mutation of K-ras by N-ethylnitrosourea shifts from codon 12 to codon 61 during fetal mouse lung maturation

Sithanandam, Gunamani; Ramakrishna, Gayatri; Diwan, Bhalchandra A.; Anderson, Lucy M.

doi:10.1038/sj.onc.1201958

Cited by 18 publications

(9 citation statements)

References 32 publications

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“…The particular mutation can also depend on the developmental age of the experimental animal. Mice exposed to the carcinogen ethylnitrosourea on day 14 of gestation developed lung tumors with frequent activating mutations in codon 12 of Ki-ras [30]. Tumors resulting from carcinogen exposure at day 18 of gestation had only codon 61 mutations.…”

Section: Discussionmentioning

confidence: 98%

Frequent codon 12 Ki-ras mutations in mouse skin tumors initiated byN-methyl-N?-nitro-N-nitrosoguanidine and promoted by mezerein

et al. 2000

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The skin tumor initiators N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 7,12-dimethylbenz[a]anthracene (DMBA) differ in effectiveness when tumor formation is promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA). Even at high doses, MNNG is less effective, producing fewer benign and malignant tumors with a longer latent period. In DMBA-initiated skin, 10 wk of TPA promotion produced a maximal tumor response. With MNNG, 20 wk of TPA promotion was required, producing nearly four times as many papillomas as 10 wk of promotion. Promotion of MNNG-initiated skin with mezerein induced the appearance of very rapidly-growing papillomas within 5 wk, 3 wk earlier than the first TPA-promoted papillomas. Thus, MNNG may induce a novel mutation resulting in a population of initiated cells that respond especially well to mezerein. Since ras mutations are common in experimental tumors in many tissues, we determined the frequency of activating mutations in the Ha-ras, Ki-ras, and N-ras oncogenes. Activating Ha-ras mutations were present in essentially all DMBA-initiated tumors and about 70% of MNNG-initiated tumors. No N-ras mutations were found in tumors lacking other ras mutations. Surprisingly, 41% of the papillomas arising in the first 11 wk in MNNG-initiated, mezerein-promoted mice bore mutations in codon 12 of the Ki-ras oncogene. Activating Ki-ras mutations were also found in more than 60% of squamous cell carcinomas and 40% of keratoacanthomas. Although mutations in Ha-ras are frequently detected in mouse skin tumors, mutations in Ki-ras are rare. This is the first report of mutated Ki-ras in skin tumors from mice initiated by MNNG.

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Section: Discussionmentioning

confidence: 98%

Frequent codon 12 Ki-ras mutations in mouse skin tumors initiated byN-methyl-N?-nitro-N-nitrosoguanidine and promoted by mezerein

et al. 2000

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“…The cells were then harvested by centrifugation for 5 min at 5,000 rpm and immediately snap-frozen. Protein extraction was performed as previously described (59). To equalize the amounts of protein loaded, the proteins were quantified using the Bradford assay following the manufacturer's recommendations (Bio-Rad).…”

Section: Methodsmentioning

confidence: 99%

Farnesol Induces Hydrogen Peroxide Resistance in Candida albicans Yeast by Inhibiting the Ras-Cyclic AMP Signaling Pathway

et al. 2010

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Farnesol, a Candida albicans cell-cell signaling molecule that participates in the control of morphology, has an additional role in protection of the fungus against oxidative stress. In this report, we show that although farnesol induces the accumulation of intracellular reactive oxygen species (ROS), ROS generation is not necessary for the induction of catalase (Cat1)-mediated oxidative-stress resistance. Two antioxidants, ␣-tocopherol and, to a lesser extent, ascorbic acid effectively reduced intracellular ROS generation by farnesol but did not alter farnesol-induced oxidative-stress resistance. Farnesol inhibits the Ras1-adenylate cyclase (Cyr1) signaling pathway to achieve its effects on morphology under hypha-inducing conditions, and we demonstrate that farnesol induces oxidative-stress resistance by a similar mechanism. Strains lacking either Ras1 or Cyr1 no longer exhibited increased protection against hydrogen peroxide upon preincubation with farnesol. While we also observed the previously reported increase in the phosphorylation level of Hog1, a known regulator of oxidative-stress resistance, in the presence of farnesol, the hog1/hog1 mutant did not differ from wild-type strains in terms of farnesol-induced oxidative-stress resistance. Analysis of Hog1 levels and its phosphorylation states in different mutant backgrounds indicated that mutation of the components of the Ras1-adenylate cyclase pathway was sufficient to cause an increase of Hog1 phosphorylation even in the absence of farnesol or other exogenous sources of oxidative stress. This finding indicates the presence of unknown links between these signaling pathways. Our results suggest that farnesol effects on the Ras-adenylate cyclase cascade are responsible for many of the observed activities of this fungal signaling molecule.

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“…Lysate preparation and fractionation were conducted as previously published, with several modifications (66). Whole-cell lysates were prepared by resuspending cells in HB buffer (10 mM Tris-HCl, pH 7.4, 150 mM NaCl, 5 mM EDTA, 10% sucrose) with protease inhibitors (Roche) and disrupting cells with glass beads in a Bio-Spec bead beater with six rounds of 50-s disruptions at 4°C and 1-min rests on ice.…”

Section: G13vmentioning

confidence: 99%

Roles of Ras1 Membrane Localization during Candida albicans Hyphal Growth and Farnesol Response

et al. 2011

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Many Ras GTPases localize to membranes via C-terminal farnesylation and palmitoylation, and localization regulates function. In Candida albicans, a fungal pathogen of humans, Ras1 links environmental cues to morphogenesis. Here, we report the localization and membrane dynamics of Ras1, and we characterize the roles of conserved C-terminal cysteine residues, C287 and C288, which are predicted sites of palmitoylation and farnesylation, respectively. GFP-Ras1 is localized uniformly to plasma membranes in both yeast and hyphae, yet Ras1 plasma membrane mobility was reduced in hyphae compared to that in yeast. Ras1-C288S was mislocalized to the cytoplasm and could not support hyphal development. Ras1-C287S was present primarily on endomembranes, and strains expressing ras1-C287S were delayed or defective in hyphal induction depending on the medium used. Cells bearing constitutively activated Ras1-C287S or Ras1-C288S, due to a G13V substitution, showed increased filamentation, suggesting that lipid modifications are differentially important for Ras1 activation and effector interactions. The C. albicans autoregulatory molecule, farnesol, inhibits Ras1 signaling through adenylate cyclase and bears structural similarities to the farnesyl molecule that modifies Ras1. At lower concentrations of farnesol, hyphal growth was inhibited but Ras1 plasma membrane association was not altered; higher concentrations of farnesol led to mislocalization of Ras1 and another G protein, Rac1. Furthermore, farnesol inhibited hyphal growth mediated by cytosolic Ras1-C288SG13V, suggesting that farnesol does not act through mechanisms that depend on Ras1 farnesylation. Our findings imply that Ras1 is farnesylated and palmitoylated, and that the Ras1 stimulation of adenylate cyclase-dependent phenotypes can occur in the absence of these lipid modifications.

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Selective mutation of K-ras by N-ethylnitrosourea shifts from codon 12 to codon 61 during fetal mouse lung maturation

Cited by 18 publications

References 32 publications

Frequent codon 12 Ki-ras mutations in mouse skin tumors initiated byN-methyl-N?-nitro-N-nitrosoguanidine and promoted by mezerein

Frequent codon 12 Ki-ras mutations in mouse skin tumors initiated byN-methyl-N?-nitro-N-nitrosoguanidine and promoted by mezerein

Farnesol Induces Hydrogen Peroxide Resistance in Candida albicans Yeast by Inhibiting the Ras-Cyclic AMP Signaling Pathway

Roles of Ras1 Membrane Localization during Candida albicans Hyphal Growth and Farnesol Response

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