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1.
Clin Oncol (R Coll Radiol) ; 28(6): 345-353, 2016 06.
Article de Anglais | MEDLINE | ID: mdl-26868286

RÉSUMÉ

AIMS: In radiotherapy trials, normal tissue effects (NTE) are important end points and it is pertinent to ask whether patient-reported outcome measures (PROMs) could replace clinical and/or photographic assessments. Data from the Standardisation of Breast Radiotherapy (START) trials are examined. MATERIALS AND METHODS: NTEs in the treated breast were recorded by (i) annual clinical assessments, (ii) photographs at 2 and 5 years, (iii) PROMs at 6 months, 1, 2 and 5 years after radiotherapy. Hazard ratios for the radiotherapy schedules were compared. Measures of agreement of assessments at 2 and 5 years tested concordance. RESULTS: PROMs were available at 2 and/or 5 years for 1939 women, of whom 1870 had clinical and 1444 had photographic assessments. All methods were sensitive to the dose difference between schedules. Patients reported a higher prevalence for all NTE end points than clinicians or photographs (P < 0.001 for most NTEs). Concordance was generally poor; weighted kappa at 2 years ranged from 0.05 (telangiectasia) to 0.21 (shrinkage and oedema). The percentage agreement was lowest between PROMs and photographic assessments of change in breast appearance (38%). CONCLUSIONS: All three methods produced similar conclusions for the comparison of trial schedules, despite low concordance between the methods on an individual patient basis. Careful consideration should be given to the different contributions of the measures of NTE in future radiotherapy trials.


Sujet(s)
Tumeurs du sein/radiothérapie , Région mammaire/effets des radiations , Fractionnement de la dose d'irradiation , Adulte , Sujet âgé , Sujet âgé de 80 ans ou plus , Diagnostic précoce , Femelle , Humains , Adulte d'âge moyen , Mesures des résultats rapportés par les patients , Pronostic , Modèles des risques proportionnels
2.
Clin Oncol (R Coll Radiol) ; 20(7): 497-501, 2008 Sep.
Article de Anglais | MEDLINE | ID: mdl-18502105

RÉSUMÉ

AIMS: Serial photographs have been collected prospectively to evaluate the effect of radiotherapy on normal tissues in the breast. The aim of this study was to compare two methods of scoring radiation-induced changes. MATERIALS AND METHODS: Five-year photographs of 400 patients randomised to receive either 42.9 or 39 Gy in 13 fractions to the whole breast after tumour excision of early breast cancer were compared with a post-surgery baseline and scored for change in breast appearance on a three-point graded scale. Two alternative methods of scoring using three observers were compared: (a) scores allocated independently, with independent resolution of discrepancies, and (b) scores allocated by consensus. RESULTS: Treatment effects estimated from the consensus and independent scores were very similar (odds ratio 1.89, 95% confidence interval 1.21-2.96 vs 2.28, 95% confidence interval 1.50-3.47, respectively). Agreement between the scores obtained from each method was reasonable, and the repeatability of the consensus method was good. CONCLUSIONS: The consensus method of scoring photographic change in breast appearance seems to be no less sensitive to randomised dose as the independent method of assessment, but is much quicker to administer. The consensus method has been used to score over 3000 sets of photographs in the National Cancer Research Institute Standardisation of Breast Radiotherapy trial.


Sujet(s)
Tumeurs du sein/radiothérapie , Photographie (méthode) , Tumeurs du sein/classification , Tumeurs du sein/chirurgie , Intervalles de confiance , Relation dose-effet des rayonnements , Femelle , Humains , Études prospectives , Radiothérapie/effets indésirables , Essais contrôlés randomisés comme sujet , Facteurs temps
3.
Lancet ; 371(9618): 1098-107, 2008 Mar 29.
Article de Anglais | MEDLINE | ID: mdl-18355913

RÉSUMÉ

BACKGROUND: The international standard radiotherapy schedule for early breast cancer delivers 50 Gy in 25 fractions of 2.0 Gy over 5 weeks, but there is a long history of non-standard regimens delivering a lower total dose using fewer, larger fractions (hypofractionation). We aimed to test the benefits of radiotherapy schedules using fraction sizes larger than 2.0 Gy in terms of local-regional tumour control, normal tissue responses, quality of life, and economic consequences in women prescribed post-operative radiotherapy. METHODS: Between 1999 and 2001, 2215 women with early breast cancer (pT1-3a pN0-1 M0) at 23 centres in the UK were randomly assigned after primary surgery to receive 50 Gy in 25 fractions of 2.0 Gy over 5 weeks or 40 Gy in 15 fractions of 2.67 Gy over 3 weeks. Women were eligible for the trial if they were aged over 18 years, did not have an immediate reconstruction, and were available for follow-up. Randomisation method was computer generated and was not blinded. The protocol-specified principal endpoints were local-regional tumour relapse, defined as reappearance of cancer at irradiated sites, late normal tissue effects, and quality of life. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN59368779. FINDINGS: 1105 women were assigned to the 50 Gy group and 1110 to the 40 Gy group. After a median follow up of 6.0 years (IQR 5.0-6.2) the rate of local-regional tumour relapse at 5 years was 2.2% (95% CI 1.3-3.1) in the 40 Gy group and 3.3% (95% CI 2.2 to 4.5) in the 50 Gy group, representing an absolute difference of -0.7% (95% CI -1.7% to 0.9%)--ie, the absolute difference in local-regional relapse could be up to 1.7% better and at most 1% worse after 40 Gy than after 50 Gy. Photographic and patient self-assessments indicated lower rates of late adverse effects after 40 Gy than after 50 Gy. INTERPRETATION: A radiation schedule delivering 40 Gy in 15 fractions seems to offer rates of local-regional tumour relapse and late adverse effects at least as favourable as the standard schedule of 50 Gy in 25 fractions.


Sujet(s)
Tumeurs du sein/radiothérapie , Radiothérapie de haute énergie/normes , Adulte , Sujet âgé , Sujet âgé de 80 ans ou plus , Tumeurs du sein/chirurgie , Fractionnement de la dose d'irradiation , Femelle , Humains , Adulte d'âge moyen , Récidive tumorale locale , Modèles des risques proportionnels , Qualité de vie , Dosimétrie en radiothérapie , Analyse de survie , Facteurs temps , Résultat thérapeutique , Royaume-Uni
4.
Lancet Oncol ; 9(4): 331-41, 2008 Apr.
Article de Anglais | MEDLINE | ID: mdl-18356109

RÉSUMÉ

BACKGROUND: The international standard radiotherapy schedule for breast cancer treatment delivers a high total dose in 25 small daily doses (fractions). However, a lower total dose delivered in fewer, larger fractions (hypofractionation) is hypothesised to be at least as safe and effective as the standard treatment. We tested two dose levels of a 13-fraction schedule against the standard regimen with the aim of measuring the sensitivity of normal and malignant tissues to fraction size. METHODS: Between 1998 and 2002, 2236 women with early breast cancer (pT1-3a pN0-1 M0) at 17 centres in the UK were randomly assigned after primary surgery to receive 50 Gy in 25 fractions of 2.0 Gy versus 41.6 Gy or 39 Gy in 13 fractions of 3.2 Gy or 3.0 Gy over 5 weeks. Women were eligible if they were aged over 18 years, did not have an immediate surgical reconstruction, and were available for follow-up. Randomisation method was computer generated and was not blinded. The protocol-specified principal endpoints were local-regional tumour relapse, defined as reappearance of cancer at irradiated sites, late normal tissue effects, and quality of life. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN59368779. FINDINGS: 749 women were assigned to the 50 Gy group, 750 to the 41.6 Gy group, and 737 to the 39 Gy group. After a median follow up of 5.1 years (IQR 4.4-6.0) the rate of local-regional tumour relapse at 5 years was 3.6% (95% CI 2.2-5.1) after 50 Gy, 3.5% (95% CI 2.1-4.3) after 41.6 Gy, and 5.2% (95% CI 3.5-6.9) after 39 Gy. The estimated absolute differences in 5-year local-regional relapse rates compared with 50 Gy were 0.2% (95% CI -1.3% to 2.6%) after 41.6 Gy and 0.9% (95% CI -0.8% to 3.7%) after 39 Gy. Photographic and patient self-assessments suggested lower rates of late adverse effects after 39 Gy than with 50 Gy, with an HR for late change in breast appearance (photographic) of 0.69 (95% CI 0.52-0.91, p=0.01). From a planned meta-analysis with the pilot trial, the adjusted estimates of alpha/beta value for tumour control was 4.6 Gy (95% CI 1.1-8.1) and for late change in breast appearance (photographic) was 3.4 Gy (95% CI 2.3-4.5). INTERPRETATION: The data are consistent with the hypothesis that breast cancer and the dose-limiting normal tissues respond similarly to change in radiotherapy fraction size. 41.6 Gy in 13 fractions was similar to the control regimen of 50 Gy in 25 fractions in terms of local-regional tumour control and late normal tissue effects, a result consistent with the result of START Trial B. A lower total dose in a smaller number of fractions could offer similar rates of tumour control and normal tissue damage as the international standard fractionation schedule of 50 Gy in 25 fractions.


Sujet(s)
Tumeurs du sein/mortalité , Tumeurs du sein/radiothérapie , Fractionnement de la dose d'irradiation , Adulte , Facteurs âges , Sujet âgé , Sujet âgé de 80 ans ou plus , Tumeurs du sein/anatomopathologie , Tumeurs du sein/chirurgie , Intervalles de confiance , Relation dose-effet des rayonnements , Femelle , Études de suivi , Humains , Estimation de Kaplan-Meier , Mastectomie partielle/méthodes , Adulte d'âge moyen , Stadification tumorale , Projets pilotes , Modèles des risques proportionnels , Dosimétrie en radiothérapie/normes , Radiothérapie adjuvante , Valeurs de référence , Appréciation des risques , Facteurs sexuels , Analyse de survie , Résultat thérapeutique , Royaume-Uni
5.
J Exp Clin Cancer Res ; 21(3 Suppl): 107-14, 2002 Sep.
Article de Anglais | MEDLINE | ID: mdl-12585664

RÉSUMÉ

The UK national study of magnetic resonance imaging as a method of screening for breast cancer (MARIBS) is in progress. The study design, accrual to date, and related research projects are described. Revised accrual rates and expected recruitment are given. 15 cancers have been detected to date, from a total of 1236 screening measurements. This event rate and the tumour grades reported are compared with recent reports from other studies in women at high risk of breast cancer.


Sujet(s)
Tumeurs du sein/diagnostic , Imagerie par résonance magnétique , Dépistage de masse , Adulte , Tumeurs du sein/génétique , Études de cohortes , Femelle , Gène BRCA1 , Gène BRCA2 , Prédisposition génétique à une maladie , Humains , Traitement d'image par ordinateur , Imagerie par résonance magnétique/méthodes , Mammographie , Adulte d'âge moyen , Mutation , Sélection de patients , Contrôle de qualité , Sensibilité et spécificité
6.
Infect Immun ; 68(3): 1109-15, 2000 Mar.
Article de Anglais | MEDLINE | ID: mdl-10678914

RÉSUMÉ

A previously described attenuated TnphoA mutant (BRD441) of Salmonella enterica serovar Typhimurium C5 (I. Miller, D. Maskell, C. Hormaeche, K. Johnson, D. Pickard, and G. Dougan, Infect. Immun. 57:2758-2763, 1989) was characterized, and the transposon was shown to be inserted in surA, a gene which encodes a peptidylprolyl-cis, trans-isomerase. A defined surA deletion mutation was introduced into S. enterica serovar Typhimurium C5 and the mutant strain, named S. enterica serovar Typhimurium BRD1115, was extensively characterized both in vitro and in vivo. S. enterica serovar Typhimurium BRD1115 was found to be defective in the ability to adhere to and invade eukaryotic cells. Furthermore, S. enterica serovar Typhimurium BRD1115 was attenuated by at least 3 log units when administered orally or intravenously to BALB/c mice. Complementation of the mutation with a plasmid carrying the intact surA gene almost completely restored the virulence of BRD1115. In addition, S. enterica serovar Typhimurium BRD1115 demonstrated potential as a vaccine candidate, since mice immunized with BRD1115 were protected against subsequent challenge with S. enterica serovar Typhimurium C5. S. enterica serovar Typhimurium BRD1115 also showed potential as a vehicle for the effective delivery of heterologous antigens, such as the nontoxic, protective fragment C domain of tetanus toxin, to the murine immune system.


Sujet(s)
Vaccins antibactériens/immunologie , Protéines de transport , Peptidylpropyl isomerase/physiologie , Salmonella typhimurium/immunologie , Administration par voie orale , Animaux , Antigènes bactériens/immunologie , Éléments transposables d'ADN , Femelle , Immunisation , Souris , Souris de lignée BALB C , Mutation , Peptidylpropyl isomerase/génétique , Salmonelloses animales/prévention et contrôle , Vaccins inactivés/immunologie
7.
Invest Ophthalmol Vis Sci ; 38(8): 1485-92, 1997 Jul.
Article de Anglais | MEDLINE | ID: mdl-9224276

RÉSUMÉ

PURPOSE: A new method for the measurement of ultraviolet radiation that reaches the surface of the eye is described. METHODS: The technique uses contact lenses produced from the ultraviolet-sensitive plastic polysulfone. Two types of polysulfone contact lenses (9 mm and 12 mm in diameter) were manufactured from a polysulfone rod. The 9-mm polysulfone contact lens could be calibrated and used to determine the ocular-to-ambient exposure ratio in a fashion similar to polysulfone film badges. The 12-mm polysulfone contact lens was designed as a "piggy-back" lens and required a larger diameter polymethlylmethacrylate carrier lens to fit the eye adequately. A method of in vivo stabilization was developed to minimize lens rotation. RESULTS: During four wearing trials, the ratio of ocular-to-ambient ultraviolet exposure ranged from 4% to 23%. CONCLUSIONS: Contact lenses manufactured from polysulfone offer the potential to study the exposure of the eye to ultraviolet radiation. The smaller diameter lens can measure an average ocular exposure, whereas the larger, stabilized, piggy-back design may allow regional dose assessment across the entire lens surface.


Sujet(s)
Oeil/effets des radiations , Rayons ultraviolets , Matériaux biocompatibles , Essais cliniques comme sujet , Lentilles de contact , Relation dose-effet des rayonnements , Conception d'appareillage , Humains , Polymères , Sulfones , Propriétés de surface
10.
Biochim Biophys Acta ; 1138(1): 68-74, 1992 Jan 16.
Article de Anglais | MEDLINE | ID: mdl-1737071

RÉSUMÉ

The cellular gene c-abl is the normal homologue of the transforming gene (v-abl) within the genome of the Abelson leukaemia virus. The cDNA sequence coding for the cellular form of the murine abl gene (c-abl type IV) has been inserted into the baculovirus transfer vector, pAc36C, so that the c-abl gene is under the control of the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). Spodoptera frugiperda cells infected with the recombinant transfer vector in the presence of wild type AcNPV DNA yielded recombinant, polyhedrin negative virus that expressed moderate levels of the c-Abl protein (representing approx. 0.5-1% of the stained cellular proteins as determined by densitometric scanning). The insect derived c-Abl protein was compared to the P210-BCR/ABL protein from K562 cells, a cell line derived from a patient with chronic myelogenous leukaemia. Antibodies raised against synthetic peptides based on c-abl encoded peptides react with the insect derived c-Abl. In addition, the baculovirus derived c-Abl protein has a tyrosine kinase activity as demonstrated by phosphorylation of a synthetic polypeptide and also by autophosphorylation. Phosphoamino acid analysis of immunoprecipitated, autophosphorylated baculovirus derived c-Abl protein indicates that the majority of label incorporated is on the tyrosine residues. Immunofluorescence microscopy has been used to show that the majority of the c-Abl protein expressed in cells infected with recombinant virus is located in the nuclear and plasma membranes.


Sujet(s)
Baculoviridae/métabolisme , Protéines proto-oncogènes c-abl/biosynthèse , Animaux , Baculoviridae/génétique , Technique de Western , Électrophorèse sur gel de polyacrylamide , Expression des gènes , Souris , Microscopie de fluorescence , Papillons de nuit/microbiologie , Phosphorylation , Tests aux précipitines , Protein kinases/métabolisme , Protéines proto-oncogènes c-abl/génétique , Protéines recombinantes/biosynthèse , Transfection
11.
FEBS Lett ; 291(2): 315-8, 1991 Oct 21.
Article de Anglais | MEDLINE | ID: mdl-1936281

RÉSUMÉ

We have overexpressed the human beta 1 thyroid hormone receptor in insect cells using a recombinant baculovirus to a level of 5-10% of total cellular protein. The recombinant protein migrates as a 50 kDa band by SDS-PAGE and Western blot analysis. The expressed receptor binds to L-T3 with a Kd of 1.3 +/- 0.4 x 10(-10) M and to thyroid hormone analogues with an affinity hierarchy of TRIAC greater than L-T3 greater than L-T4 greater than rT3. Gel retardation assays show highly specific receptor binding to a TRE which is modified by the presence of ligand and avidin-biotin complex DNA analysis shows a Kd of 6.2 +/- 2.0 x 10(-10) M for this interaction. These results indicate high level expression of hTR beta with authentic hormone and DNA binding properties.


Sujet(s)
Baculoviridae/génétique , Vecteurs génétiques , Récepteurs des hormones thyroïdiennes/génétique , Animaux , Séquence nucléotidique , Technique de Western , Électrophorèse sur gel de polyacrylamide , Humains , Données de séquences moléculaires , Papillons de nuit/génétique , Récepteurs des hormones thyroïdiennes/biosynthèse , Protéines recombinantes/biosynthèse , Protéines recombinantes/génétique
12.
J Biol Chem ; 266(3): 1672-8, 1991 Jan 25.
Article de Anglais | MEDLINE | ID: mdl-1899093

RÉSUMÉ

Kirsten-ras is the oncogene most frequently activated in human tumors. Studies of its biological function have been limited by the nonavailability of significant amounts of the major protein product, Kirsten-ras (4B) p21. When expressed in Escherichia coli K12, the recombinant protein was rapidly cleaved upon cell lysis in the lysine-rich C terminus region, probably by the ompT protease. However, soluble full-length protein was obtained when the Kirsten-ras gene was expressed in an E. coli strain lacking the ompT gene, and also in a baculovirus/insect cell expression system. Additionally, the baculovirus/insect cell system produced about half of the Kirsten-ras protein in a membrane-associated form, which was post-translationally modified by polyisoprenylation and carboxyl-methylation. A C-terminally truncated form (residues 1-166) was also expressed at high levels in E. coli for x-ray crystallographic studies. The kinetics of GDP release and of GTP hydrolysis of the purified proteins are similar to those of the corresponding Harvey-ras proteins, though there are small differences in the relative affinities for GDP and GTP. Biological activity of full-length Kirsten Val-12 p21 was demonstrated by microinjection into Swiss 3T3 cells, resulting in morphological transformation, with a lower potency than that of Harvey Val-12 protein.


Sujet(s)
Protéines proto-oncogènes p21(ras)/génétique , Animaux , Baculoviridae , Transformation cellulaire néoplasique , Cellules cultivées , Cristallographie , Escherichia coli , Protéines G/composition chimique , Protéines G/génétique , Protéines G/isolement et purification , Protéines G/métabolisme , Expression des gènes , Vecteurs génétiques , Techniques in vitro , Insectes , Point isoélectrique , Souris , Maturation post-traductionnelle des protéines , Protéines proto-oncogènes p21(ras)/composition chimique , Protéines proto-oncogènes p21(ras)/isolement et purification , Protéines proto-oncogènes p21(ras)/métabolisme , Protéines recombinantes , Diffraction des rayons X
13.
Biotechnology (N Y) ; 9(1): 64-8, 1991 Jan.
Article de Anglais | MEDLINE | ID: mdl-1367214

RÉSUMÉ

We have cloned the light and heavy chain cDNAs for the humanized monoclonal antibody Campath-1H and expressed them in Chinese hamster ovary (CHO) cells using a dihydrofolate reductase (dhfr) amplification procedure. Each cDNA was positioned under control of the strong human beta-actin promoter/polyadenylation signals and used to evaluate alternative vector design and amplification procedures. By employing a dual selection co-transfection strategy, initial transformants accumulated antibody levels of 0.5 micrograms/ml after 4 days continuous culture. When subjected to successive rounds of selection in medium containing stepwise increments in methotrexate (MTX), stable cell lines were obtained that secreted up to 200 micrograms/ml of Campath-1H during the same period. This reflects a productivity of 100 micrograms/10(6) cells/day and demonstrates the potential of engineering CHO cells for the production of recombinant antibodies.


Sujet(s)
Anticorps monoclonaux/biosynthèse , Antigènes CD/immunologie , Antigènes néoplasiques , Glycoprotéines , Actines/génétique , Animaux , Anticorps monoclonaux/génétique , Anticorps monoclonaux/métabolisme , Cellules productrices d'anticorps/métabolisme , Antigène CD52 , Cellules cultivées , Clonage moléculaire , Cricetinae , Cricetulus , ADN/génétique , Femelle , Amplification de gène , Expression des gènes , Vecteurs génétiques/physiologie , Humains , Cinétique , Myélome multiple/génétique , Myélome multiple/anatomopathologie , Rats , Protéines recombinantes/biosynthèse , Protéines recombinantes/génétique , Protéines recombinantes/métabolisme , Cellules cancéreuses en culture
14.
Proc Natl Acad Sci U S A ; 87(17): 6883-7, 1990 Sep.
Article de Anglais | MEDLINE | ID: mdl-2395882

RÉSUMÉ

Many estrogen-antagonist and -agonist ligands have been synthesized, some of which have proved clinically important in the treatment of hormone-dependent breast tumors and endocrine disorders. Here we show that the "pure" antiestrogen ICI 164,384 inhibits mouse estrogen receptor-DNA binding in vitro. The effects of this steroid on DNA binding can be overcome by addition of anti-receptor antibody whose epitope lies N-terminal to the receptor DNA-binding domain. Since this antibody is also capable of restoring DNA-binding activity to receptor mutants that either lack the dimerization domain or bear deleterious mutations within it, we propose that ICI 164,384 reduces DNA binding by interfering with receptor dimerization. In contrast, when complexed with the antagonist/partial agonist tamoxifen, the estrogen receptor is capable of binding to DNA in vitro, but tamoxifen does not promote the agonist-induced conformational change obtained with estradiol. The implications of these data are discussed in relation to the in vivo properties of these drugs.


Sujet(s)
ADN/métabolisme , Oestradiol/analogues et dérivés , Antagonistes des oestrogènes/pharmacologie , Récepteurs des oestrogènes/métabolisme , Séquence d'acides aminés , Animaux , Anticorps , Technique de Western , Lignée cellulaire , Délétion de segment de chromosome , Clonage moléculaire , Oestradiol/pharmacologie , Cellules HeLa/métabolisme , Humains , Données de séquences moléculaires , Mutation , Peptides/synthèse chimique , Polydésoxyribonucléotides/métabolisme , Amides gras polyinsaturés N-alkylés , Liaison aux protéines , Récepteurs des oestrogènes/effets des médicaments et des substances chimiques , Récepteurs des oestrogènes/génétique , Cartographie de restriction , Transfection
15.
Oncogene ; 5(7): 1045-8, 1990 Jul.
Article de Anglais | MEDLINE | ID: mdl-2197592

RÉSUMÉ

Using the insect/baculovirus expression system, we demonstrate the incorporation of [3H]mevalonate and [3H]methyl groups into recombinant c-Ha-ras protein (p21). Unlike the post-translational palmitoylation of p21 expressed in this system, the modification by mevalonate is not removed by hydroxylamine suggesting the absence of a thioester linkage. It is highly likely that the insect expression system recognizes the C-terminal CAAX Motif in p21, incorporates the mevalonate into the recently described polyisoprenylation modification and carboxyl-methylates the protein.


Sujet(s)
Acide mévalonique/métabolisme , Protéine oncogène p21(ras)/métabolisme , Séquence d'acides aminés , Animaux , Cellules cultivées , Esters , Expression des gènes , Techniques in vitro , Virus des insectes , Insectes , Données de séquences moléculaires , Polyéthylène glycols , Maturation post-traductionnelle des protéines , Protéines recombinantes/métabolisme , Solubilité , Relation structure-activité
16.
J Biol Chem ; 264(32): 19147-54, 1989 Nov 15.
Article de Anglais | MEDLINE | ID: mdl-2681210

RÉSUMÉ

Normal and mutated cDNAs of Ha-ras have each been cloned into a standard (pAc373) and a novel (p36C) baculovirus transfer vector and introduced via homologous recombination into the genome of Autographa californica nuclear polyhedrosis virus immediately downstream of the polyhedrin promoter. Spodoptera frugiperda cells infected with recombinant virus containing the normal Ha-ras gene express very high levels of ras p21 protein (approximately 20% of total cell protein), whereas the mutant protein was expressed at considerably lower levels. Molecular analysis showed that this was most likely due to a post-transcriptional event. The expression vector p36C produced considerably higher levels of recombinant p21 compared to the more commonly used pAc373. The majority of the normal ras p21 protein is soluble, cytoplasmic, and appears to be nonacylated. However, about 10% of the p21 associates with the membrane fraction of infected cells and migrates as a slightly faster band on gels. Furthermore, this band is sensitive to hydroxylamine treatment and shows specific incorporation of [3H]palmitate, strongly suggesting that it is the palmitoylated form of p21, which is the biologically active form of the protein. Both the soluble and membrane-associated p21 have been purified to homogeneity under nondenaturing conditions, the latter in the presence of detergents. The isolation of native palmitoylated p21 has not been reported previously. The difference in hydrophobicity between these two proteins has been demonstrated by Triton X-114 partitioning. The use of the insect/baculovirus expression system to express relatively high levels (20 mg/liter) of palmitoylated p21 should aid experiments to resolve the structural and functional properties of this molecule.


Sujet(s)
Expression des gènes , Virus des insectes/génétique , Protéine oncogène p21(ras)/génétique , Séquence d'acides aminés , Animaux , Séquence nucléotidique , Technique de Western , ADN/génétique , Gènes ras , Vecteurs génétiques , Insectes , Données de séquences moléculaires , Masse moléculaire , Mutation , Protéine oncogène p21(ras)/biosynthèse , Protéine oncogène p21(ras)/isolement et purification , Acide palmitique , Acides palmitiques/métabolisme , Protéines recombinantes/biosynthèse , Protéines recombinantes/isolement et purification , Cartographie de restriction
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