Patient perspective on zanamivir in the treatment of influenza

Placebo-controlled clinical studies have shown zanamivir to be an effective treatment of influenza A and influenza B illness. This survey, conducted in France, was done to evaluate patients' perception of zanamivir in clinical practice. Between January and mid-April 2000, 271 retail pharmacists gave questionnaires to patients with a prescription for zanamivir to be completed on a voluntary basis. A total of 514 patients returned completed questionnaires, of whom 97 (19%) were considered at high risk of developing influenza complications. Fifty-one (10%) patients, mainly those over 65 years, were vaccinated against influenza. Fever or feverishness was reported by 93% of patients, and cough, myalgia and headache by 72%. Most (58%) patients consulted their doctor within 24 hours of the onset of symptoms, and 96% within 48 hours. Eighty-five per cent of patients overall and 82% of high-risk individuals (82/97) reported being satisfied with their zanamivir treatment. Treatment compliance was high with 75% of patients completing the whole course of treatment. Symptom relief was reported by 45% of patients within 24 hours and by 74% of patients within 48 hours; 66% of patients resumed normal activities within 72 hours. These results suggest that patient satisfaction is high and compliance with zanamivir is highly satisfactory. In addition, the use of zanamivir was reported to be associated with rapidsymptom relief and return to normal activity

Cost-effectiveness of urinary dipsticks to screen asymptomatic catheter-associated urinary infections in an intensive care unit

OBJECTIVE

To assess the cost-effectiveness of urinary dipsticks (UDs) to screen asymptomatic catheterized patients for quantitative urine.

DESIGN

Prospective comparison of UD with quantitative urine culture (QUC) (reference technique) and cost-effectiveness analysis performed from the hospital's perspective.

SETTING

Medical intensive care unit (ICU) of the Besançon University Hospital (France).

PATIENTS AND PARTICIPANTS

All consecutive, asymptomatic, catheterized patients.

INTERVENTIONS

Urinary dipsticks (Multistix 8-SG) were analyzed by the reflectance spectrophotometric method (Clinitek 50). Sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) of four combinations of the leukocyte (L) test pad and the nitrite (N) test pad were calculated: L and N, L or N, L alone and N alone. A micro-costing technique was used to determine the direct medical cost of each strategy. The calculated cost-effectiveness ratio was the incremental cost-effectiveness (ICE) ratio.

MEASUREMENTS AND RESULTS

Three hundred thirty-nine urine samples taken from 144 patients were analyzed. The incidence of asymptomatic catheter-associated urinary tract infections (CAUTIs) was 31.3% (> or =10(5) organisms/ml). The L or N combination was the best detector of asymptomatic CAUTI: Se=87.2%, Sp=61.6%, PPV=30.6% and NPV=96.1%. The cost of QUC strategy and UD strategy was EUR 21.5 and EUR 12.6 per test, respectively. The ICE ratio of QUCs was EUR 69.5 per case of detected CAUTI.

CONCLUSION

The UD is a cost-effective test for screening asymptomatic catheterized patients for quantitative urine culture in a medical ICU.

Polymorphisms of human aryl hydrocarbon receptor (AhR) gene in a French population: relationship with CYP1A1 inducibility and lung cancer

The Ah receptor (AhR) is a ligand-dependent transcription factor that positively regulates the expression of the CYP1A1 gene. We investigated the genetic polymorphisms of the AhR gene including the promoter, and examined the link between these polymorphisms, CYP1A1 inducibility and the lung cancer incidence. The AhR promoter region and the 11 exons of 30 subjects were screened. Among the three polymorphisms found, two [(2417)(A/G) ((157)G/A)] have never been described previously. The (1721)(G/A) and (2417)(A/G) are localized in exon 10 and lead to Arg(554)Lys and Met(786)Val substitutions, respectively. The other polymorphism was found in the 5'-untranslated region, resulting in the substitution of a G by an A at position 157 (157)(G/A). To evaluate the frequency of this allelic variant found, a DNA library of a case-control study of lung cancer (162 controls and 177 patients) was studied. There is no significant association between (1721)(G/A), (157)(G/A) and lung cancer: (1721)(G/A) and (157)(G/A) were detected at the same allele frequency of 0.086 and 0.25, respectively in both controls and patients. (2417)(A/G) was found in only one control of 100 (allele frequency 0.005). Statistical analysis did not show any relationship between both (1721)(G/A) and (157)(G/A) polymorphisms found and CYP1A1 inducibility. Considering the rareness of the (2417)(A/G) allelic variant we were not able to evaluate its association with inducibility. In conclusion, none of the polymorphisms were found to play a key role in the CYP1A1 inducibility or in the susceptibility to develop lung cancer.

Silk fibroin: structural implications of a remarkable amino acid sequence

The amino acid sequence of the heavy chain of Bombyx mori silk fibroin was derived from the gene sequence. The 5,263-residue (391-kDa) polypeptide chain comprises 12 low-complexity "crystalline" domains made up of Gly-X repeats and covering 94% of the sequence; X is Ala in 65%, Ser in 23%, and Tyr in 9% of the repeats. The remainder includes a nonrepetitive 151-residue header sequence, 11 nearly identical copies of a 43-residue spacer sequence, and a 58-residue C-terminal sequence. The header sequence is homologous to the N-terminal sequence of other fibroins with a completely different crystalline region. In Bombyx mori, each crystalline domain is made up of subdomains of approximately 70 residues, which in most cases begin with repeats of the GAGAGS hexapeptide and terminate with the GAAS tetrapeptide. Within the subdomains, the Gly-X alternance is strict, which strongly supports the classic Pauling-Corey model, in which beta-sheets pack on each other in alternating layers of Gly/Gly and X/X contacts. When fitting the actual sequence to that model, we propose that each subdomain forms a beta-strand and each crystalline domain a two-layered beta-sandwich, and we suggest that the beta-sheets may be parallel, rather than antiparallel, as has been assumed up to now.

Incidence and risk factors of preparation errors in a centralized cytotoxic preparation unit

OBJECTIVE

A major objective of centralized preparation is to improve the quality of the final product, and thus their safety for the patient. Few data are available concerning errors occurring during preparation and the risk factors associated with the errors. To assess risk factors associated with preparation errors in a centralized cytotoxic preparation unit.

DESIGN

Medication errors were detected during preparation (self-education by technicians) or at the time of control (qualitative and semi-quantitative). For each preparation, several potential risk factors were studied. Univariate analysis was carried out using Chi-2 or Fisher exact tests. Variables with p < 0.15 associated in univariate analysis were entered in a stepwise regression model. In an overall analysis, all types of error were considered. In a second analysis, only major errors (errors associated with drug, dose or major incompatibility) were studied.

RESULTS

Analysis included 30,819 preparations. Overall and major error rates were respectively 0.45% and 0.19%. The number of bottles (more than one), the volume of active solution (more than 50 ml) and the daily workload were the major risk factors identified by successive univariate and multivariate analysis.

CONCLUSION

Low rates of medication errors compared to previous studies were reported. Major preparation errors were principally related to drug labeling (dose/bottle and concentration) and workload. Preparation mistakes appeared to have many causes. These results could be used to revise the general organization and determine a suitable purchasing policy.

Relation between inducibility of CYP1A1, GSTM1 and lung cancer in a French population

Smoking is the principal cause of lung cancer. However, not all smokers will develop this disease. Individual susceptibility to chemically induced cancer may be explained in part by genetic differences in the activation and detoxification of procarcinogens. The activation phase of polycyclic aromatic hydrocarbon (PAH) metabolism is governed by the enzyme CYP1A1, induced by PAH when it enters the body. The extent to which PAH induces CYP1A1 activity varies greatly from one subject to another. CYP1A1 inducibility has long been associated, although inconsistently, with an increased risk of lung cancer. In 1982, Kouri corroborated Kellerman's results with a new method for measuring inducibility, but few studies have reported using this method. The glutathione S-transferases (GSTs) are involved in the detoxification phase of PAH, and the allelic deletion of GSTM1 has been also associated with an increased risk of lung cancer. We conducted a case-control study to examine the risk of lung cancer related, separately and together, to CYP1A1 inducibility, GSTM1 polymorphism and cigarette smoking in a French population. The 611 subjects were 310 incident lung cancer cases and 301 hospital control subjects. We were able to constitute a DNA bank for 552 subjects (89.5%) and gather detailed information on smoking history for all of them. Inducibility could be measured for 195 cases and 183 control subjects. Results for GSTM1 polymorphism concern 247 cases and 254 control subjects. GSTM1 polymorphism and inducibility could both be assessed for 179 cases and 166 control subjects. The odds ratio related to inducibility was 1.7 [1.0-3.0] for medium and 3.1 (1.3-7.4) for hyper inducers. The association with GSTM1 was 1.6 (1.0-2.6). With a reference category of subjects who were both low inducers and GSTM1(+), we found an odds ratio for lung cancer of 8.1 (2-31) for the subjects with both risk factors [i.e. GSTM1(-) and hyper inducers]. Our data did not reveal evidence of interaction between smoking and inducibility. On the other hand, we found an interaction of 3.6 (0.6-21) between inducibility and GSTM1.

The genomic structure of c14orf1 is conserved across eukarya

We have recently cloned the gene C14orf1, which is strongly expressed in normal testis and in several cancer cell lines and tumors. This gene maps to 14q24.3 and is interrupted by four introns. Two of them are also represented in the open reading frame of Schizosaccharomyces pombe in the same phase. In Arabidopsis taliana only the first of the two introns was found, in the same phase as the corresponding ones in S. pombe and human. Disruption of the ortholog in Saccharomyces cerevisiae (Yer044c) led to a severe growth defect, and C14orf1 failed to complement mutant yeast when put under the control of the natural Yer044c promoter. Further studies are needed to understand the causes underlying the high degree of conservation of the C14orf1 genomic structure.

MSI1 suppresses hyperactive RAS via the cAMP-dependent protein kinase and independently of chromatin assembly factor-1

RAS hyperactivation in the yeast Saccharomyces cerevisiae leads to multiple nutritional growth defects associated with overstimulation of the cAMP signaling pathway. Hyperactive RAS can be suppressed by overexpression of MSI1, a subunit of chromatin assembly factor-1 (yCAF-1). MSI1 overexpression suppresses phenotypes induced by increased cAMP content in multiple genetic backgrounds. However, MSI1 does not inhibit cAMP synthesis or total cellular cAMP-dependent protein kinase (PKA) activity, nor does MSI1 stimulate expression of several cAMP-repressible genes critical for the acquisition of thermotolerance in the stationary phase. Our analysis indicates that yCAF-1 is dispensable for inhibition of hyperactive RAS by MSI1. We demonstrate that in the presence of the PKA regulatory subunit, BCY1, MSI1 inhibits phenotypes of a mutationally activated PKA catalytic subunit. These observations indicate that MSI1 affects PKA function in a BCY1-dependent manner via mechanisms other than direct overall inhibition of PKA catalytic activity. MSI1 appears to provide two distinct roles in chromatin modeling as a component of yCAF-1, and in the inhibition of RAS signaling by modulating PKA.

Functional cloning of the adenylate cyclase gene of Candida albicans in Saccharomyces cerevisiae within a genomic fragment containing five other genes, including homologues of CHS6 and SAP185

We have cloned a genomic fragment of Candida albicans by complementation of a Saccharomyces cerevisiae cyr1 mutant. This fragment contains the two-thirds C-terminal part of the adenylate cyclase CaCYR1. The complete gene has been sequenced from PCR fragments amplified from genomic DNA, and contains an ORF of 1690 amino acids closely related to other fungal adenylate cyclases. Adjacent to the adenylate cyclase gene, we have sequenced six other putative genes. CaCHS6, CaYNL191 and CaYJL098 are named on the basis of their close similarity with S. cerevisiae genes. ORFs CaYJL097a and CaYJL097b represent two repeated homologues of the S. cerevisiae YJL097w, which probably arose from an ancient duplication. The last one is a hypothetical ORF, CaYKR049, which presents only a very weak similarity with YKR049. The S. cerevisiae homologues of three of these genes are co-localized on chromosome X but with a different order and orientation.

Fine organization of Bombyx mori fibroin heavy chain gene

The complete sequence of the Bombyx mori fibroin gene has been determined by means of combining a shotgun sequencing strategy with physical map-based sequencing procedures. It consists of two exons (67 and 15 750 bp, respectively) and one intron (971 bp). The fibroin coding sequence presents a spectacular organization, with a highly repetitive and G-rich (approximately 45%) core flanked by non-repetitive 5' and 3' ends. This repetitive core is composed of alternate arrays of 12 repetitive and 11 amorphous domains. The sequences of the amorphous domains are evolutionarily conserved and the repetitive domains differ from each other in length by a variety of tandem repeats of subdomains of approximately 208 bp which are reminiscent of the repetitive nucleosome organization. A typical composition of a subdomain is a cluster of repetitive units, Ua, followed by a cluster of units, Ub, (with a Ua:Ub ratio of 2:1) flanked by conserved boundary elements at the 3' end. Moreover some repeats are also perfectly conserved at the peptide level indicating that the evolutionary pressure is not identical along the sequence. A tentative model for the constitution and evolution of this unusual gene is discussed.

Cost-effectiveness of CD34+ dose in peripheral blood progenitor cell transplantation for non-Hodgkin's lymphoma patients: a single centre study

Intensive high-dose chemotherapy with peripheral blood progenitor cell (PBPC) transplantation is a common strategy for aggressive non-Hodgkin's lymphomas (NHL). A retrospective cost-effectiveness analysis of CD34+ cell dose was carried out. Between 1994 and 1998, 28 patients were included. Efficacy was measured by the length of aplasia. Data collection concerned the period from graft day until discharge from hospital, and the post-graft period until graft day +100. Patients transplanted using a cell dose greater than 5 x 106/kg were found to have a faster hematological recovery. Average length of post-graft hospitalization was shorter and fewer blood products were required for patients with more than 5 x 106/kg CD34+ cells transplanted. Hospitalization was the major cost driver. A large reduction in procedure cost was obtained with a CD34+ cell count higher than 5 x 106/kg (-US$2740, -11%). This difference was directly related to hospitalization (-US$860) and platelet units transfused (-US$1,340). A sensitivity analysis showed the robustness of results. Our findings indicated that a CD34+ cell dose higher than 5 x 106/kg was more cost-effective than a lower dose in NHL patients. The collection of 5 x 106/kg CD34+ cells appeared necessary to optimize the PBPC procedure.

[Prescriptions of aerosol therapy. A survey of practices at the Besançon University Hospital]

OBJECTIVE

Prescriptions of aerosol sprays concomitantly with other drugs can raise problems of incompatibility.

METHODS

Medical practices in the clinical units of the Besançon University Hospital were analyzed to assess the therapeutic indications, the most frequently prescribed drugs, possible admixtures, the nature and volume of solvents used, drug protocols and type of aerosol therapy and nebulizer used. Sixty questionnaires were sent to all the units of the University Teaching Hospital of Besançon.

RESULTS

Analysis of 48 questionnaires completed by head nurses showed that 28 different drugs and 26 different admixtures were prescribed. Only 2 of the admixtures had undergone prior validation. Only 7 (26%) of the drug formulations prescribed had received marketing approval. Recognized clinical practices for the administration of aerosol therapy were not applied and the aerosol sessions were not standardized.

CONCLUSION

Many prescriptions are carried out without knowledge of the chemical compatibility of co-administered medicines.

Selection of genes repressed by cAMP that are induced by nutritional limitation in Saccharomyces cerevisiae

DNA-lacZ fusion libraries of yeast Saccharomyces cerevisiae were used to select genes coordinately regulated by the Ras-cAMP-cAPK signalling pathway. Sixteen new genes (AGP1, APE2, APE3, FPS1, GUT2, MDH2, PLB2, PYK2, RNR3, SUR1, UGA1, YHR033w, YBR006w, YHR143w, YMR086w and YOR173w) were found to be repressed by cAMP. Most of these genes encode for metabolic enzymes and are induced by nutritional limitations. These common properties suggest a role of this pathway in the metabolic adjustment of the cell to nutritional variations. The induction of 10 of these genes is reduced in the msn2,msn4 double mutant, which emphasizes the role of the Msn2/4p transcriptional activators in mediating the Ras-cAMP-cAPK signalling pathway. The Msn2p/Msn4p-independent expression of the six other genes suggests the existence of other regulatory systems under the control of this pathway.

In vitro capacitation of dog spermatozoa as assessed by chlortetracycline staining

We developed an assay for detecting capacitation and acrosome status in dog spermatozoa using chlortetracycline (CTC) as a fluorescent probe. Sperm cells were stained after incubation in modified canine capacitation medium (mCCM). Calcium ionophore A23187 permitted the induction of acrosomal exocytosis of capacitated sperm cells. Spermac staining and transmission electron microscopy were used as control tests to detect acrosome-reacted spermatozoa. Three different patterns of CTC distribution in the spermatozoa were found. These patterns were similar to those observed in other mammalian species. The CTC test was used to monitor the time course of the capacitation process in dogs. It was found that the kinetics of capacitation in canine sperm cells are similar to those observed in other mammals.

The heat shock response in yeast: differential regulations and contributions of the Msn2p/Msn4p and Hsf1p regulons

The heat shock transcription factor Hsf1p and the stress-responsive transcription factors Msn2p and Msn4p are activated by heat shock in the yeast Saccharomyces cerevisiae. Their respective contributions to heat shock protein induction have been analysed by comparison of mutants and wild-type strains using [35S]-methionine labelling and two-dimensional gel electrophoresis. Among 52 proteins induced by a shift from 25 degrees C to 38 degrees C, half of them were found to be dependent upon Msn2p and/or Msn4p (including mostly antioxidants and enzymes involved in carbon metabolism), while the other half (including mostly chaperones and associated proteins) were dependent upon Hsf1p. The two sets of proteins overlapped only slightly. Three proteins were induced independently of these transcription factors, suggesting the involvement of other transcription factor(s). The Ras/cAMP/PKA signalling pathway cAMP had a negative effect on the induction of the Msn2p/Msn4p regulon, but did not affect the Hsf1p regulon. Thus, the two types of transcription factor are regulated differently and control two sets of functionally distinct proteins, suggesting two different physiological roles in the heat shock cellular response.

Medication errors at the administration stage in an intensive care unit

OBJECTIVE

To assess the type, frequency and potential clinical significance of medication-administration errors.

DESIGN

Prospective study using the observation technique as described by the American Society of HealthSystem Pharmacists but eliminating the disguised aspect.

SETTING

Medical intensive care unit (ICU) in a university hospital.

PATIENTS AND PARTICIPANTS

2009 medication administration interventions by nurses.

INTERVENTIONS

Pharmacist-performed observation of preparation and administration of medication by nurses, comparison with the original medical order and comparison with the data available in the literature.

MEASUREMENTS AND RESULTS

132 (6.6% of 2009 observed events) errors were detected. Their distribution is as follows: 41 dose errors, 29 wrong rate, 24 wrong preparation technique, 19 physicochemical incompatibility, 10 wrong administration technique and 9 wrong time errors. No fatal errors were observed, but 26 of 132 errors were potentially life-threatening and 55 potentially significant.

CONCLUSION

According to this first observation-based study of medication administration errors in a European ICU, these errors were due to deficiencies in the overall organisation of the hospital medication track, in patient follow-up and in staff training.

[Incomplete prescription: a potential medication error]

OBJECTIVE

According to the American Society of Health System Pharmacists, an incomplete or imprecise medial order comprises a prescription error. Such errors have potential consequences in terms of mortality, morbidity, prolonged hospital stay and, finally, in health care expenditure. The aim of this study was to determine the rate of incomplete prescriptions observed in a university hospital setting and identify the causes of such imprecisions.

METHODS

A prospective analysis of prescriptions for oral medicines ordered by an internal medicine unit of a university hospital was conducted on a daily basis by a pharmaceutical team immediately after the orders were written. A complete prescription was defined as one with the following information: unit dose, formulation, number of doses per day, hour of administration, particular instructions for use.

RESULTS

Among the 241 prescription lines analyzed during a 20 day period, 131 (54.2%) were incomplete. The number of doses per day was missing for 7.9%, unit dose for 6.2%, particular instructions for 4.9% and the formulation for 2.9%.

DISCUSSION

These findings demonstrated the lack of quality of the prescriptions studied. A treatment scheme totally incompatible with quality prescriptions and a poor understanding of prescription quality were the most probable causes. These two elements reflect the gap between the outdated organizational scheme currently in use and appropriate implementation of the hospital drug distribution circuit.

Ssa1p chaperone interacts with the guanine nucleotide exchange factor of ras Cdc25p and controls the cAMP pathway in Saccharomyces cerevisiae

We have found that the guanine nucleotide exchange factor for ras, Cdc25p, interacts with Ssa1p in Saccharomyces cerevisiae. This interaction was observed with GST-fused Cdc25p polypeptides and confirmed by coimmunoprecipitation with the endogenous Cdc25p. Hsp82 appeared also to be co-immunoprecipitated with Cdc25p, albeit to a lower level than Hsp70. In a strain deleted for SSA1 and SSA2, we observed a reduced cellular content of Cdc25p. Consistent with a reduced activity of the cAMP-dependent PKA pathway, the rate of accumulation of both trehalose and glycogen was stimulated in the ssa-deleted strain. Expression of SSA1 reversed these effects, whereas co-expression of SSA1 and PDE2 restored high accumulation. The expression of genes repressed by cAMP, GAC1 and TPS1, fused to beta-galactosidase, was also stimulated by deletion of SSA genes. The effect of ssa deletion on glycogen accumulation was lost in a strain deleted for CDC25 rescued by the RAS2ile152 allele. Altogether, these results lead to the conclusion that Ssa1p positively controls the cAMP pathway through Cdc25p. We propose that this connection plays a critical role in the adaptation of cells to stress conditions.

Msn2p and Msn4p control a large number of genes induced at the diauxic transition which are repressed by cyclic AMP in Saccharomyces cerevisiae

The multicopy suppressors of the snf1 defect, Msn2p and Msn4p transcription factors (Msn2/4p), activate genes through the stress-responsive cis element (CCCCT) in response to various stresses. This cis element is also the target for repression by the cyclic AMP (cAMP)-signaling pathway. We analyzed the two-dimensional gel electrophoresis pattern of protein synthesis of the msn2 msn4 double mutant and compared it with that of the wild-type strain during exponential growth phase and at the diauxic transition. Thirty-nine gene products (including those of ALD3, GDH3, GLK1, GPP2, HSP104, HXK1, PGM2, SOD2, SSA3, SSA4, TKL2, TPS1, and YBR149W) are dependent upon Msn2/4p for their induction at the diauxic transition. The expression of all these genes is repressed by cAMP. Thirty other genes identified during this study are still inducible in the mutant. A subset of these genes were found to be superinduced at the diauxic transition, and others were subject to cAMP repression (including ACH1, ADH2, ALD6, ATP2, GPD1, ICL1, and KGD2). We conclude from this analysis that Msn2/4p control a large number of genes induced at the diauxic transition but that other, as-yet-uncharacterized regulators, also contribute to this response. In addition, we show here that cAMP repression applies to both Msn2/4p-dependent and -independent control of gene expression at the diauxic shift. Furthermore, the fact that all the Msn2/4p gene targets are subject to cAMP repression suggests that these regulators could be targets for the cAMP-signaling pathway.

Dimerization of Cdc25p, the guanine-nucleotide exchange factor for Ras from Saccharomyces cerevisiae, and its interaction with Sdc25p

The oligomerization state of Cdc25p, the guanine nucleotide exchange factor for ras from yeast, was analyzed using different complementary approaches. The two-hybrid system showed that the C-terminal part of Cdc25p (Cdc25-Ct) can interact with itself but also with Sdc25p-Ct, the corresponding part of Sdc25p, the other guanine exchange factor from yeast. The homotropic interaction of Cdc25p-Ct has been confirmed in yeast using immunoprecipitation experiments with epitope-tagged and beta-galactosidase-fused polypeptides. No other component was required for this interaction, since dimerization was shown to occur with material synthesized in vitro. The size of Cdc25-Ct produced in Escherichia coli has been directly measured on gel filtration columns and corresponds to a dimer. The dimerization domain is localized in the same part of the molecule as the catalytic domain and the portion responsible for membrane localization. The biological relevance of dimerization is still an open question, however by allowing heterodimerization with Sdc25p it could permit a more complex combinatorial regulation of ras in yeast.

The Ktr1p, Ktr3p, and Kre2p/Mnt1p mannosyltransferases participate in the elaboration of yeast O- and N-linked carbohydrate chains

We have determined a role for Ktr1p and Ktr3p as mannosyltransferases in the synthesis of the carbohydrate chains attached to Saccharomyces cerevisiae O- and N-modified proteins. KTR1 and KTR3 encode related proteins that are highly similar to the Kre2p/Mnt1p Golgi alpha1,2-mannosyltransferase (Lussier, M., Camirand, A., Sdicu, A.-M., and Bussey, H. (1993) Yeast 9, 1057-1063; Mallet, L., Bussereau, F., and Jacquet, M. (1994) Yeast 10, 819-831). Examination of the electrophoretic mobility of a specifically O-linked protein from mutants and an analysis of their total O-linked mannosyl chains demonstrates that Ktr1p, Ktr3p, and Kre2p/Mnt1p have overlapping roles and collectively add most of the second and the third alpha1,2-linked mannose residues on O-linked oligosaccharides. Determination of the mobility of the specifically N-linked glycoprotein invertase in different null strains indicates that Ktr1p, Ktr3p, and Kre2p are also jointly involved in N-linked glycosylation, possibly in establishing some of the outer chain alpha1,2-linkages.

The nucleotide sequence of Saccharomyces cerevisiae chromosome XIV and its evolutionary implications

In 1992 we started assembling an ordered library of cosmid clones from chromosome XIV of the yeast Saccharomyces cerevisiae. At that time, only 49 genes were known to be located on this chromosome and we estimated that 80% to 90% of its genes were yet to be discovered. In 1993, a team of 20 European laboratories began the systematic sequence analysis of chromosome XIV. The completed and intensively checked final sequence of 784,328 base pairs was released in April, 1996. Substantial parts had been published before or had previously been made available on request. The sequence contained 419 known or presumptive protein-coding genes, including two pseudogenes and three retrotransposons, 14 tRNA genes, and three small nuclear RNA genes. For 116 (30%) protein-coding sequences, one or more structural homologues were identified elsewhere in the yeast genome. Half of them belong to duplicated groups of 6-14 loosely linked genes, in most cases with conserved gene order and orientation (relaxed interchromosomal synteny). We have considered the possible evolutionary origins of this unexpected feature of yeast genome organization.

Yeast RAS2 mutations modulating the ras-guanine exchange factor interaction

We have used a two-hybrid approach to test various forms of Saccharomyces cerevisiae Ras2p for their ability to interact with the human guanine nucleotide exchange factor HGRF55. We have previously shown that a strong two-hybrid interaction is found between the HGRF55p and the dominant negative Ras2p(G22A) form of ras [Camus et al. (1995) Oncogene 11, 951-959]. We show here that the substitution N123I which weakens the guanine nucleotide binding also promotes ras-GEF interaction. We demonstrate that the R80D substitution alone completely abolishes the interaction of Ras2p(G22A) with GEF, whereas substitutions at positions 81, 82 and 73 have only small effects. Since residue 73 is involved in the response of ras to GEF, we propose that it plays a role in the conformational change induced by the GEF rather than in its binding. Those results emphasize the role of the alpha2 helix of the switch II region in the recognition of the GEF family.