Salvage neck surgery in recurrent nodal NPC: Do all patients require a comprehensive neck dissection in the modern MRI era?

OBJECTIVE

The standard treatment for regional failure in nasopharyngeal carcinoma (NPC) is the radical neck dissection (RND). Our study sought to determine if magnetic resonance imaging (MRI) may accurately predict nodal involvement to allow selected levels of neck dissection to be preserved.

STUDY DESIGN AND SETTING

We analysed retrospectively all NPC patients in our centre undergoing neck dissections as salvage therapy for nodal recurrence. Nodal involvement based on the preoperative MRI was assessed and compared with postoperative histopathology.

METHODS

This is a retrospective study conducted on patients in our centre with recurrent NPC from February 2002 to February 2017. Patients were identified from the database of the otolaryngology oncology division at our institution. Of these, 28 patients met all our inclusion and exclusion criteria. We calculated sensitivity and specificity as well as average number of nodes per patient.

RESULTS

In our study, we calculated the false negative and false positive rates of preoperative MRI neck by levels. Overall sensitivity of MRI picking up disease by level was 76% and specificity was 86%.

CONCLUSION

Based on our study, we will be missing a total of 10 (7.1%) diseased neck levels in eight (28.5%) patients. MRI alone, therefore, does not provide enough information to allow safe selective preservation of neck levels in surgical salvage of neck recurrences in NPC.

COVID-19, circuit breaker and safe reopening - perspective from an ENT practice at a tertiary hospital in Singapore

COVID-19 has affected every walk of life, including the healthcare sector. In this article, we discuss how an Otolaryngology department in a tertiary hospital in Singapore had to adapt to the pandemic in areas of outpatient care, elective surgeries, personal protection, residency training, education and research. Documenting our experience has helped us to understand the areas of work which can be affected in a pandemic and the factors that have helped to mitigate disruption. This will prove useful in our approach to subsequent pandemics.

Olfactory taste disorder as a presenting symptom of COVID-19: a large single-center Singapore study

Purpose

To investigate the prevalence and epidemiological risk factors of olfactory and/or taste disorder (OTD), in particular isolated OTD, in patients with laboratory-confirmed COVID-19 infection.

Methods

We conducted a retrospective and cross-sectional study. Patients with laboratory-confirmed COVID-19 infection were recruited from the National Centre for Infectious Diseases (NCID) Singapore between 24 March 2020 and 16 April 2020. The electronic health records of these patients were accessed, and demographic data and symptoms reported (respiratory, self-reported OTD and other symptoms such as headache, myalgia and lethargy) were collected.

Results

A total of 1065 patients with laboratory-confirmed COVID-19 were recruited. Overall, the prevalence of OTD was 12.6%. Twelve patients (1.1%) had isolated OTD. The top three symptoms associated with OTD were cough, fever and sore throat. The symptoms of runny nose and blocked nose were experienced by only 29.8 and 19.3% of patients, respectively. Multivariate analysis demonstrated that the female gender, presence of blocked nose and absence of fever were significantly associated with OTD (adjusted relative risks 1.77, 3.31, 0.42, respectively). All these factors were statistically significant.

Conclusion

Patients with COVID-19 infection can present with OTD, either in isolation or in combination with other general symptoms. Certain demographic profile, such as being female, and symptomatology such as the presence of blocked nose and absence of fever, were more likely to have OTD when infected by COVID-19. Further studies to elucidate the pathophysiology of OTD in these patients will be beneficial.

Author Correction: Merkel cell polyomavirus activates LSD1-mediated blockade of non-canonical BAF to regulate transformation and tumorigenesis

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Merkel cell polyomavirus activates LSD1-mediated blockade of non-canonical BAF to regulate transformation and tumorigenesis

Merkel cell carcinoma (MCC), a neuroendocrine cancer of the skin, is caused by integration of Merkel cell polyomavirus (MCV) and persistent expression of Large T antigen (LT) and Small T antigen (ST). We report that ST in complex with MYCL and the EP400 complex activates expression of LSD1 (KDM1A), RCOR2, and INSM1 to repress gene expression by the lineage transcription factor ATOH1. LSD1 inhibition reduces growth of MCC in vitro and in vivo. Through a forward-genetics CRISPR-Cas9 screen, we identified an antagonistic relationship between LSD1 and the non-canonical BAF (ncBAF) chromatin remodeling complex. Changes in gene expression and chromatin accessibility caused by LSD1 inhibition could be partially rescued by BRD9 inhibition, revealing that LSD1 and ncBAF antagonistically regulate an overlapping set of genes. Our work provides mechanistic insight into the dependence of MCC on LSD1 and a tumor suppressor role for ncBAF in cancer.

Evaluating False Transfer Rates from the Match-between-Runs Algorithm with a Two-Proteome Model

Stochasticity between independent LC-MS/MS runs is a challenging problem in the field of proteomics, resulting in significant missing values (i.e., abundance measurements) among observed peptides. To address this issue, several approaches have been developed including computational methods such as MaxQuant's match-between-runs (MBR) algorithm. Often dozens of runs are all considered at once by MBR, transferring identifications from any one run to any of the others. To evaluate the error associated with these transfer events, we created a two-sample/two-proteome approach. In this way, samples containing no yeast lysate (n = 20) were assessed for false identification transfers from samples containing yeast (n = 20). While MBR increased the total number of spectral identifications by ∼40%, we also found that 44% of all identified yeast proteins had identifications transferred to at least one sample without yeast. However, of these only 2.7% remained in the final data set after applying the MaxQuant LFQ algorithm. We conclude that false transfers by MBR are plentiful, but few are retained in the final data set.

Vitamin D Binding Protein and Vitamin D Levels in Multi-Ethnic Population

INTRODUCTION

Low levels of 25-hydroxyvitamin D (25(OH)D) has been associated with many negative health outcomes including falls and fractures. 25(OH)D is largely bound to vitamin D binding protein (VDBP). There is increasing evidence that free or bioavailable 25(OH)D may be a better measure of vitamin D deficiency.

OBJECTIVE

To determine the prevalence of 25(OH)D deficiency and VDBP levels in multi-ethnic population, and its impact on muscle strength.

DESIGN AND METHODS

Cross-sectional study of older adults in Western region of Singapore. 295 participants from three ethnic groups were selected from the Healthy Older People Everyday (HOPE) cohort for measurements of total 25(OH)D and VDBP levels. Total 25(OH)D, VDBP, frailty status, Timed-Up-and-Go (TUG) and grip strength (GS) were assessed. Albumin, free and bioavailable 25(OH)D were only available for 256 participants.

RESULTS

53% of Malay and 55% of Indians were deficient in 25(OH)D compared with 18.2% of ethnic Chinese participants. Chinese also had higher total 25(OH)D concentrations with a mean of 29.1 ug/l, (p = <0.001). Chinese had the lowest level of VDBP (169.6ug/ml) followed by Malay (188.8 ug/ml) and Indian having the highest (220.1 ug/ml). Calculated bioavailable and free 25(OH)D levels were significantly higher in Chinese, followed by Malays and Indians, which also correlated with better grip strength measures amongst the Chinese.

CONCLUSION

The Malays and Indians had overall lower free, bioavailable and total 25(OH)D compared with ethnic Chinese. Chinese ethnic group also had the lowest VDBP and better overall grip strength.

Improved Method for Determining Absolute Phosphorylation Stoichiometry Using Bayesian Statistics and Isobaric Labeling

Phosphorylation stoichiometry, or occupancy, is one element of phosphoproteomics that can add useful biological context (Gerber et al. Proc. Natl. Acad. Sci. U. S. A. 2003, 100, 6940-5). We previously developed a method to assess phosphorylation stoichiometry on a proteome-wide scale (Wu et al. Nat. Methods 2011, 8, 677-83). The stoichiometry calculation relies on identifying and measuring the levels of each nonphosphorylated counterpart peptide with and without phosphatase treatment. The method, however, is problematic in that low stoichiometry phosphopeptides can return negative stoichiometry values if measurement error is larger than the percent stoichiometry. Here, we have improved the stoichiometry method through the use of isobaric labeling with 10-plex TMT reagents. In this way, five phosphatase treated and five untreated samples are compared simultaneously so that each stoichiometry is represented by five ratio measurements with no missing values. We applied the method to determine basal stoichiometries of HCT116 cells growing in culture. With this method, we analyzed five biological replicates simultaneously with no need for phosphopeptide enrichment. Additionally, we developed a Bayesian model to estimate phosphorylation stoichiometry as a parameter confined to an interval between 0 and 1 implemented as an R/Stan script. Consequently, both point and interval estimates are consistent with the plausible range of values for stoichiometry. Finally, we report absolute stoichiometry measurements with credible intervals for 6772 phosphopeptides containing at least a single phosphorylation site.

Thrombin generation and cell-dependent hypercoagulability in sickle cell disease

Essentials Sickle cell disease is increasingly being recognized as a chronic hypercoagulable state. Thrombin generation is elevated in the whole blood, but not the plasma of sickle cell patients. Whole blood thrombin generation inversely correlates to erythrocyte phosphatidylserine exposure. Acquired protein S deficiency is likely explained by binding of protein S to sickle red cells. Click to hear Dr Hillery discuss coagulation and vascular pathologies in mouse models of sickle cell disease.

SUMMARY

Introduction Sickle cell disease (SCD) is a hypercoagulable state with chronic activation of coagulation and an increased incidence of thromboembolic events. However, although plasma pre-thrombotic markers such as thrombin-anithrombin complexes and D-dimer are elevated, there is no consensus on whether global assays of thrombin generation in plasma are abnormal in patients with SCD. Based on our recent observation that normal red blood cells (RBCs) contribute to thrombin generation in whole blood, we hypothesized that the cellular components in blood (notably phosphatidylserine-expressing erythrocytes) contribute to enhanced thrombin generation in SCD. Methods Whole blood and plasma thrombin generation assays were performed on blood samples from 25 SCD patients in a non-crisis 'steady state' and 25 healthy race-matched controls. Results Whole blood thrombin generation was significantly elevated in SCD, whereas plasma thrombin generation was paradoxically reduced compared with controls. Surprisingly, whole blood and plasma thrombin generation were both negatively correlated with phosphatidylserine exposure on RBCs. Plasma thrombin generation in the presence of exogenous activated protein C or soluble thrombomodulin revealed deficiencies in the protein C/S anticoagulant pathway in SCD. These global changes were associated with significantly lower plasma protein S activity in SCD that correlated inversely with RBC phosphatidylserine exposure. Conclusion Increased RBC phosphatidylserine exposure in SCD is associated with acquired protein S deficiency. In addition, these data suggest a cellular contribution to thrombin generation in SCD (other than RBC phosphatidylserine exposure) that explains the elevated thrombin generation in whole blood.

PM10 mass concentration and oxidative capacity of moxa smoke

BACKGROUND

The burning of moxa floss in moxibustion releases moxa smoke containing a substantial amount of particulate matter (PM10) into the environment, which has generated safety concerns about its potential health impact.

DESIGN

Plasmid scission assay was performed using PM10 collected from moxibustion clinics.

METHODS

PM10 was collected in winter 2012 by burning three types of moxa floss samples in moxibustion simulation clinics, and the resulting PM10 mass concentration was calculated. Oxidative capacity of the PM10 samples was measured by plasmid scission assay and the percentage of DNA damage at dosage 500 µg ml(-1) (D500) was calculated by linear regression analysis.

RESULTS

The average PM10 mass concentration of samples A (3 years and 3:1 ratio), B (3 years and 8:1 ratio) and C (10 years and 3:1 ratio) was 273.33, 172.22 and 168.89 μg/m(3), respectively. The D500 oxidative capacity of PM10 was on average 24.25%, 27.83% and 28.07% for samples A, B and C, respectively. No significant difference was found in the PM10-induced oxidative damage by moxa smoke produced from the three types of moxa floss.

CONCLUSIONS

PM10 mass concentrations from the three types of moxa floss combustion exceeded internationally recommended levels. Despite so, PM10 mass concentration of moxa smoke was much lower than biomass and coal combustion and similar to that of gas combustion. The oxidative DNA damage induced by individual PM10 in moxibustion environment was lower than that reported in other environments, indicating that moxibustion-derived PM10 might not be as injurious to human health as generally assumed.

Arthroscopic resection of The Distal Clavicle With Concomitant Subacromial Decompression: A Case Series

Shoulder impingement syndrome and acromioclavicular joint osteoarthritis often occur simultaneously and easily missed. Kay et al. reported excellent results with combined arthroscopic subacromial decompression and resection of the distal end of the clavicle in patients with both disorders¹. Arthroscopic treatment of these disorders produces more favourable results than open procedures. We report two patients who were not responding to conservative management and were treated with direct arthroscopic distal clavicle excision and subacromial decompression in single setting. Both patients gained good postoperative outcome in terms of pain score, function and strength improvement assessed objectively with visual analogue score (VAS) and University of California Los Angeles Score (UCLA).

Rituximab as first-line treatment for the management of adult patients with non-severe hemophilia A and inhibitors

BACKGROUND

The role of immunosuppression in the management of patients with congenital hemophilia and inhibitors is uncertain. The use of rituximab has been limited to case reports and case series. In most reports, rituximab was used as second-line or third-line treatment following failure of conventional immune tolerance induction therapy, and more commonly in pediatric patients.

OBJECTIVES

The objective of this study was to describe our experience with rituximab for the eradication of factor VIII inhibitors in adult patients with non-severe hemophilia A.

PATIENTS

We retrospectively reviewed the medical records of adult patients with non-severe hemophilia A and a diagnosis of FVIII inhibitor treated with rituximab (four weekly doses of 375 mg m(-2) ) as first-line treatment at our hemophilia center.

RESULTS

We identified nine consecutive adult patients with hemophilia A (moderate, n = 5; mild, n = 4) at our institution between 2000 and 2013, with a median age of 54 years (range, 24-77 years) at the time of inhibitor diagnosis. No patient received concomitant immune tolerance induction therapy. All nine patients had successful eradication of FVIII inhibitors. The median time from the first dose of rituximab to a clinical response was 95 days (range, 12-278 days). The median follow-up was 56 months (range, 13-139 months). Following inhibitor eradication, eight patients were rechallenged with FVIII concentrates. Two patients developed inhibitor recurrence associated with surgery.

CONCLUSION

This case series demonstrates that rituximab is a useful first-line treatment to achieve sustained inhibitor eradication in adult patients with non-severe hemophilia A.

Relationship between family meals away from home and nutritional status of adolescents

INTRODUCTION

Despite the many benefits of family meals, data on association between family meals away from home (FMAFH) and nutritional status of adolescents is limited. This study determined the association between FMAFH with dietary intake and body mass index of adolescents (N = 408).

METHODS

Data were obtained through interviewer-administered questionnaire and anthropometric measurements of adolescents.

RESULTS

Respondents comprised 53.7% females, 67.6% Chinese with the mean age of sample being 13.7 +/- 0.6 years old. Generally, male adolescents had higher intakes of energy, macronutrients and micronutrients. All nutrients except calcium (51.3%), iron (females--54.7%) and vitamin A (females--86.1%) met the recommended intakes. A higher proportion of male (25.4%) than female (13.6%) adolescents were overweight and obese. About 44% of respondents had family meals > or = 7 times in the previous week with 48.9% reported having family meals at home > or = 7 times weekly. The majority (91.2%) of adolescents had FMAFH at least once a week either at restaurants (53%), fast food outlets (41.6%), food courts in shopping complexes (40%) or food stalls (30.2%). As the frequency of FMAFH increased, there was an increasing trend in energy and energy-adjusted nutrient intakes. However, only energy-adjusted fat intake was significantly high (p < 0.05) in adolescents having FMAFH > 7 times weekly. No significant association was observed for frequency of FMAFH and body mass index.

CONCLUSION

With increasing dependence on foods outside the home, FMAFH can be a source of healthy diet for families provided they have the knowledge, skills and motivation to make healthy food choices.

Allergic rhinitis: evidence-based practice

Allergic rhinitis is a common condition in Singapore, with a considerable disease burden. This article reviews the latest evidence-based concepts and current understanding of the disease, including its aetiology, pathogenesis, signs and symptoms, investigations as well as management. Particular attention is given to reviewing principles that will aid the management of this disease from a practical point of view, and the latest evidence for the various pharmacological options as well as immunotherapy is discussed. The article should be of interest to otolaryngologists as well as allergists, respiratory physicians and family practitioners.

An in vitro comparison of the bleaching efficacy of 35% carbamide peroxide with established intracoronal bleaching agents

AIM

To evaluate the bleaching efficacy of 35% carbamide peroxide, 35% hydrogen peroxide and sodium perborate for intracoronal bleaching of root filled discoloured teeth.

METHODOLOGY

Extracted premolars were artificially stained using whole blood then root canal treatment was performed. After obturation, a 2 mm intermediate base was placed 1 mm below the buccal amelo-cemental junction. Intracoronal bleaching was performed in 11 teeth per group, using either 35% carbamide peroxide gel (group CP), 35% hydrogen peroxide gel (group HP) or sodium perborate mixed with distilled water (group SP). The bleaching agents were replaced after 7 days. The shade of the teeth was evaluated at day 0, 7 and 14. The results were analysed using Kruskal-Wallis one-way analysis of variance and Mann-Whitney U-test.

RESULTS

At the end of 7 days, both groups CP and HP lightened by 8 +/- 3 Vita tab positions, respectively, whereas group SP lightened by 5 +/- 3 tab positions (P < 0.05). At the end of the second bleaching period at day 14, group CP and HP lightened by a further 2 +/- 2 and 2 +/- 3 tab positions, respectively, whereas group SP lightened by a further 3 +/- 4 tab positions. There were no statistical differences between groups at day 14.

CONCLUSIONS

Thirty-five per cent carbamide peroxide and 35% hydrogen peroxide were equally effective for intracoronal bleaching, and significantly better than sodium perborate after 7 days. After 14 days, there were no significant differences between the groups. Thirty-five per cent carbamide peroxide can be recommended as an equally effective alternative to hydrogen peroxide for intracoronal bleaching.

Light- and electron-microscopic analysis of neuropeptide Y-immunoreactive amacrine cells in the guinea pig retina

We investigated the morphology and synaptic connections of neuropeptide Y (NPY)-containing neurons in the guinea pig retina by immunocytochemistry, using antisera against NPY. Specific NPY immunoreactivity was localized to a population of wide-field and regularly spaced amacrine cells with processes ramifying mainly in stratum 1 of the inner plexiform layer (IPL). Double-label immunohistochemistry demonstrated that all NPY-immunoreactive cells possessed glutamic acid decarboxylase 65 immunoreactivity. The synaptic connectivity of NPY-immunoreactive amacrine cells was identified in the IPL by electron microscopy. The NPY-labeled amacrine cell processes received synaptic input from other amacrine cell processes and bipolar cell axon terminals in stratum 1 of the IPL. The most frequent postsynaptic targets of NPY-immunoreactive amacrine cells were other amacrine cell processes. Synaptic outputs to bipolar cells were also observed in a small number of cases. This finding suggests that NPY-containing amacrine cells may influence inner retinal circuitry in stratum 1 of the IPL, thus mediating visual processing.

The pattern of lymphoma in east Malaysian patients as experienced in the University Hospital, Kuala Lumpur

Lymphoma is a highly heterogeneous group of malignant disease. This study aimed to elucidate the pattern of lymphoma in the East Malaysian patient population. 107 cases of confirmed lymphomas from East Malaysian biopsy material were retrieved from the files of the Department of Pathology, University of Malaya, in the 3-year period between 1981 to 1983. With the use of a panel of lymphoid antibodies, the disease was sub-classified using the Rye classification for Hodgkin's lymphoma (HL) and the REAL classification for non-Hodgkin's lymphoma (NHL). All of the cases were tested for the presence of the Epstein-Barr virus by EBER-ISH. There were 11 (10.3%) HL, 80 (74.7%) B-NHL and 16 (15%) T-NHL. The HL:NHL ratio was 1:9. The most common tumour in children was Burkitt's lymphoma 7/13 (53.8%). In the adult group, there were 72/94 (76.6%) B-NHL ¿diffuse large cell type 51 (of which 2 were CD30+), Burkitt's lymphoma 8, follicular lymphoma 5, low grade MALT 2, mantle cell type 1 and not otherwise specified due to poor morphology 5¿, 13/94 (13.8%) T-NHL and 9/94 (9.6%) HL. Of the 9 adult HL, the most common subtype was nodular sclerosis (6, 66.7%). The EBER positive rate in classical HL, T-NHL, BL and B-NHL were 33.3%, 56.3%, 60.0% and 3.1% respectively. In conclusion, the spectrum of lymphoma seen in East Malaysia was rather similar to West Malaysia except for the very low prevalence of peripheral T-cell lymphoma (PTCL) in Sarawak (3.3%).

Enhanced dissolution of gallstone by combining ethanol with two commonly used cholelitholytic solvents

BACKGROUND/AIMS

Contact dissolution therapy is one of the non-surgical treatments for patients with gallstone. Among the various solvents, methyl tert-butyl ether (MTBE) is used for cholesterol gallstone, while tetrasodium ethyl-dimethyl tetraacetate (EDTA-4Na) solution is used to dissolve calcium bilirubinate stones. However, the contents of gallstone cannot be precisely predicted while they are still present in the human body. This study was designed to test if the MTBE and EDTA can be mixed together and to test the solubility of different kinds of gallstone in each original solution and mixture.

METHODOLOGY

Each 0.1 gm of mixed cholesterol stone, brown stone and pigment stone from 18 patients was used. Pure ethanol was chosen to enhance the miscibility between the organic phase of MTBE and the aqueous phase of EDTA. The contents of gallstone after dissolution were examined with scanning electromicroscopy.

RESULTS

We found the mixture of ethanol, MTBE and EDTA to be the most efficient solvent in gallstone dissolution in comparison with the other two original solvents. The mixture reached a dissolution percentage of 97.96 +/- 1.00, 88.96 +/- 6.51 and 67.75 +/- 14.26 for cholesterol, brown and black pigment gallstone, respectively.

CONCLUSIONS

We concluded that ethanol can be used to mix the MTBE and EDTA with good preservation in their litholytic effects on gallstone. The ethanol-MTBE-EDTA solvent is, therefore, a promising universal cholelitholytic agent which deserves further tests for its safety and efficacy in the in vivo study.

Characterization of a Helicobacter pylori vaccine candidate by proteome techniques

In a previous two-dimensional (2D) gel electrophoretic study of protein antigens of the gastric pathogen, Helicobacter pylori recognized by human sera, one of the highly and consistently reactive antigens, a protein with Mr of approximately 30,000 (Spot 15) seemed to be of special interest because of low yields on N-terminal protein sequencing. This suggested possible N-terminal modification, as the N-terminal sequence analysis of this 30,000 protein (Spot 15) did not provide a definitive match within the H. pylori genomic database. This protein was isolated by 2D polyacrylamide gel electrophoresis, evaluated by liquid chromatography-mass spectrometry, and found to consist of two related species of approximately 28,100 and 26,500. In parallel, the proteins within this spot were digested in situ with the endoprotease Lys-C. Analysis of the Lys-C digest by matrix-assisted laser desorption time-of-flight mass spectrometry, peptide mapping, and sequence analysis was conducted. Comparison of the mass and sequence of the Lys-C peptides with those derived from a H. pylori genomic library identified an open reading frame of approximately 300 base pairs as the source of the Spot 15 protein. This corresponded to HP0175 in the recently reported H. pylori genome sequence, an open reading frame with some homology to Campylobacter jejeuni cell binding protein 2. Mass spectral and sequence analysis indicated that Spot 15 was a processed product generated by proteolytic cleavage at both the carboxy and amino termini of the 34 open reading frame precursor.

Identification of potential diagnostic and vaccine candidates of Helicobacter pylori by two-dimensional gel electrophoresis, sequence analysis, and serum profiling

There is great interest in characterizing the proteins of the gastric pathogen Helicobacter pylori, especially those to which humans respond immunologically, because of the potential importance of such proteins in diagnosis and vaccine development. Two-dimensional gel electrophoresis was used to separate and identify potential antigens of H. pylori ATCC 43504. Over 30 proteins were reactive in Western blots with pooled sera from 14 infected patients. These proteins were analyzed by N-terminal sequence analysis. Fourteen proteins were determined to be distinct from any proteins previously described from H. pylori; the others were previously isolated and characterized proteins. Analysis of eight distinct H. pylori strains showed that most of these antigens were produced by all of the strains. We propose that collection of new antigens such as those recognized here will be useful in serologic tests for detecting and monitoring H. pylori infection and may also serve as potential targets for antimicrobial agent or vaccine development.

Sequence variation and phylogenetic analysis of envelope glycoprotein of hepatitis G virus

A transfusion-transmissible agent provisionally designated hepatitis G virus (HGV) was recently identified. In this study, we examined the variability of the HGV genome by analysing sequences in the putative envelope region from 72 isolates obtained from diverse geographical sources. The 1561 nucleotide sequence of the E1/E2/NS2a region of HGV was determined from 12 isolates, and compared with three published sequences. The most variability was observed in 400 nucleotides at the N terminus of E2. We next analysed this 400 nucleotide envelope variable region (EV) from an additional 60 HGV isolates. This sequence varied considerably among the 75 isolates, with overall identity ranging from 79.3% to 99.5% at the nucleotide level, and from 83.5% to 100% at the amino acid level. However, hypervariable regions were not identified. Phylogenetic analyses indicated that the 75 HGV isolates belong to a single genotype. A single-tier distribution of evolutionary distances was observed among the 15 E1/E2/NS2a sequences and the 75 EV sequences. In contrast, 11 isolates of HCV were analysed and showed a three-tiered distribution, representing genotypes, subtypes, and isolates. The 75 isolates of HGV fell into four clusters on the phylogenetic tree. Tight geographical clustering was observed among the HGV isolates from Japan and Korea.

Overexpression of the yeast MCK1 protein kinase suppresses conditional mutations in centromere-binding protein genes CBF2 and CBF5

We find that overexpression in yeast of the yeast MCK1 gene, which encodes a meiosis and centromere regulatory kinase, suppresses the temperature-sensitive phenotype of certain mutations in essential centromere binding protein genes CBF2 and CBF5. Since Mck1p is a known serine/threonine protein kinase, this suppression is postulated to be due to Mck1p-catalyzed in vivo phosphorylation of centromere binding proteins. Evidence in support of this model was provided by the finding that purified Mck1p phosphorylates in vitro the 110 kDa subunit (Cbf2p) of the multimeric centromere binding factor CBF3. This phosphorylation occurs on both serine and threonine residues in Cbf2p.

Yeast MCK1 protein kinase autophosphorylates at tyrosine and serine but phosphorylates exogenous substrates at serine and threonine

The product of the Saccharomyces cerevisiae MCK1 gene is a protein kinase that phosphorylates poly (Glu,Tyr) in vitro and is itself phosphorylated at both tyrosine and serine in vivo. To characterize the substrate specificity of Mck1, the enzyme was purified to apparent homogeneity from the soluble fraction of yeast cell extracts by ammonium sulfate precipitation, followed by ion exchange chromatography (Q- and S-Sepharose), dye-ligand affinity chromatography (Orange A-agarose), adsorption chromatography (hydroxylapatite), and ion exchange fast protein liquid chromatography (Mono-S). In the absence of an exogenous substrate, purified Mck1 was able to autophosphorylate on tyrosine and serine. A catalytically inactive mutant (K68R in conserved kinase domain II) expressed in an mck1 delta strain did not contain detectable phosphotyrosine, confirming that the tyrosine phosphorylation observed in vivo is due to autophosphorylation, but did contain phosphoserine, suggesting that Mck1 is a target for other cellular protein kinases. Purified Mck1 phosphorylated a variety of proteins in heat-inactivated yeast extracts, primarily on serine (and threonine). The purified enzyme also used a number of mammalian proteins as phosphoacceptors, including myelin basic protein (MBP), microtubule-associated protein 2 (MAP-2), and tau protein. All of these substrates were phosphorylated on either serine or threonine (or both). Mck1 isolated from yeast extracts by immunoprecipitation with an anti-Mck1 antibody directed against its C terminus also phosphorylated MBP at serine. In the same immune complex kinase assay, the K68R mutant did not detectably phosphorylate MBP, indicating that the serine-specific phosphotransferase activity of Mck1 is intrinsic and not due to contamination by an associated kinase. These findings demonstrate that Mck1 is a member of a novel class of protein kinases that displays the ability to phosphorylate all three hydroxyamino acids in proteins.

Novel yeast protein kinase (YPK1 gene product) is a 40-kilodalton phosphotyrosyl protein associated with protein-tyrosine kinase activity

Extracts of bakers' yeast (Saccharomyces cerevisiae) contain protein-tyrosine kinase activity that can be detected with a synthetic Glu-Tyr copolymer as substrate (G. Schieven, J. Thorner, and G.S. Martin, Science 231:390-393, 1986). By using this assay in conjunction with ion-exchange and affinity chromatography, a soluble tyrosine kinase activity was purified over 8,000-fold from yeast extracts. The purified activity did not utilize typical substrates for mammalian protein-tyrosine kinases (enolase, casein, and histones). The level of tyrosine kinase activity at all steps of each preparation correlated with the content of a 40-kDa protein (p40). Upon incubation of the most highly purified fractions with Mn-ATP or Mg-ATP, p40 was the only protein phosphorylated on tyrosine. Immunoblotting of purified p40 or total yeast extracts with antiphosphotyrosine antibodies and phosphoamino acid analysis of 32P-labeled yeast proteins fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the 40-kDa protein is normally phosphorylated at tyrosine in vivo. 32P-labeled p40 immunoprecipitated from extracts of metabolically labeled cells by affinity-purified anti-p40 antibodies contained both phosphoserine and phosphotyrosine. The gene encoding p40 (YPK1) was cloned from a yeast genomic library by using oligonucleotide probes designed on the basis of the sequence of purified peptides. As deduced from the nucleotide sequence of YPK1, p40 is homologous to known protein kinases, with features that resemble known protein-serine kinases more than known protein-tyrosine kinases. Thus, p40 is a protein kinase which is phosphorylated in vivo and in vitro at both tyrosine and serine residues; it may be a novel type of autophosphorylating tyrosine kinase, a bifunctional (serine/tyrosine-specific) protein kinase, or a serine kinase that is a substrate for an associated tyrosine kinase.

The v-rel oncogene product is complexed with cellular proteins including its proto-oncogene product and heat shock protein 70

The oncogene product, pp59v-rel, of avian reticuloendotheliosis virus (REV-T) is complexed in the cytosol of REV-T transformed lymphoid cells with cellular proteins. Monoclonal antibodies and antisera directed against different regions of pp59v-rel coimmunoprecipitate five cellular proteins (p124, p115, p75, p70, and p40) in addition to pp59v-rel. Cellular proteins with the same apparent molecular mass also copurify with pp59v-rel during sequential Sephacryl S200 and immunoaffinity chromatography. Antisera directed against the most abundant cellular protein in the complex, pp40, coimmunoprecipitate pp59v-rel and several cellular proteins with the same apparent molecular mass. The 75-kDa protein in the pp59v-rel complex is the product of c-rel proto-oncogene and is weakly phosphorylated. In MSB-1 cells this protein is not detectably phosphorylated or associated with cellular proteins. The 70-kDa protein in the pp59v-rel containing cytosolic complex is the constitutive form of avian heat shock protein 70 (HSC70). The p70 protein coimmunoprecipitates and copurifies with pp59v-rel using antisera directed against pp59v-rel and coimmunoprecipitates with antisera specific for pp40. The p70 isolated from immune complexes containing pp59v-rel shares V8 protease fragments with HSC70.

Avian reticuloendotheliosis virus-transformed lymphoid cells contain multiple pp59v-rel complexes

The v-rel oncogene of avian reticuloendotheliosis virus type T (REV-T) encodes a 59-kilodalton (kDa) phosphoprotein located principally in the cytosol of transformed lymphoid cells. All of the detectable pp59v-rel was present in high-molecular-weight complexes containing at least five cellular proteins (p124, p115, p75c-rel, p70hsc, and pp40). Antiserum was developed against the 40-kDa protein, the most abundant cellular protein associated with the complex. The 40-kDa phosphoprotein was complexed with pp59v-rel in REV-T-transformed lymphoid cell lines arrested at different stages of B-cell development as well as in lymphoid tumor cells and in fibrosarcomas. The half-life (8 h) of pp40 in REV-T-transformed lymphoid cells was the same as that of pp59v-rel. Antiserum against pp40 permitted the identification of two pp59v-rel complexes. The most abundant cytoplasmic complex contained approximately 75% of the pp59v-rel and all of the detectable pp40 in REV-T-transformed lymphoid cells. Twenty-five percent of the pp59v-rel was present in a minor complex that contained the majority of p75c-rel along with p115 and p124. In nuclear extracts of REV-T-transformed lymphoid cells, pp59v-rel was complexed with pp40. The two high-molecular-weight proteins (p115 and p124) and p75c-rel were not detected in the nuclear complex. In the cytosolic complexes, pp40 was heavily phosphorylated, whereas the nuclear form was much less extensively phosphorylated.

The v-rel oncogene product is complexed to a 40-kDa phosphoprotein in transformed lymphoid cells

The transforming protein encoded by the v-rel oncogene of avian reticuloendotheliosis virus (REV-T) is a very low copy number molecule in the cytosol of transformed cells. Analysis of cytosolic extracts from a REV-T-transformed lymphoid cell line by gel filtration on Sephacryl S-300 indicated that most of the v-rel oncogene product, pp59v-rel, eluted with an apparent molecular mass of 400 kDa. The size of this complex was confirmed by analysis on a fast-protein liquid chromatography gel filtration column. A 40-kDa cellular protein copurified with pp59v-rel on sequential gel filtration on Sephacryl S-200 and immunoaffinity chromatography with a monoclonal antibody directed against pp59v-rel. The 40-kDa cellular protein could also be immunoprecipitated together with pp59v-rel from cell extracts of [35S]methionine-labeled cells, suggesting that pp59v-rel is complexed with the 40-kDa protein in transformed lymphoid cells. Both the 59- and 40-kDa proteins were phosphorylated when the highly purified preparation containing pp59v-rel was incubated with [gamma-32P]ATP and 10 mM MgCl2 in vitro. The identity of the kinase in the highly purified preparation containing pp59v-rel, however, is unknown. Immune complexes recovered from extracts of REV-T-transformed lymphoid cells labeled with [32P]orthophosphate also contained the 59- and 40-kDa phosphoproteins. These observations suggest that pp59v-rel is complexed with a 40-kDa cellular phosphoprotein to form a 400-kDa heteropolymer in the cytoplasm of transformed lymphoid cells.

Rearrangements of chicken immunoglobulin genes in lymphoid cells transformed by the avian retroviral oncogene v-rel

The retroviral oncogene v-rel transforms poorly characterized lymphoid cells. We have explored the nature of these cells by analyzing the configuration and expression of immunoglobulin genes in chicken hemopoietic cells transformed by v-rel. None of the transformed cells expressed their immunoglobulin genes. The cells fell into three classes: class I cells have their immunoglobulin genes potentially in an embryonic configuration; class II and class III cells have lost one copy of the lambda light chain locus and have one copy of the heavy chain locus rearranged into a configuration that differs from what is found in mature B cells. In class II cells, the other heavy chain locus may be in embryonic configuration, whereas it is deleted in class III cells. The first of these classes may represent the earliest stage of the lymphoid lineage yet encountered among virus-transformed cells, whereas the second and third classes represent an apparently anomalous rearrangement whose origin remains unknown.

The transforming protein of avian reticuloendotheliosis virus is a soluble cytoplasmic protein which is associated with a protein kinase activity

We have identified the product (p57v-rel) of the transforming gene, v-rel, of avian reticuloendotheliosis virus (REV-T) using antisera generated against nonoverlapping sequences representing the middle and carboxy-terminal regions of the v-rel protein expressed in Escherichia coli (N.K. Herzog and H.R. Bose, Jr., 1986, Proc. Natl. Acad. Sci. USA 83, 812-816). The amino-terminal region of the v-rel protein was also expressed in E. coli and used to generate antisera. The immunoglobulin-enriched fractions of these antisera were used to determine the subcellular location of p57v-rel in REV-T transformed lymphoid cells. Cells were fractionated into nuclear, mitochondrial, microsomal, and cytoplasmic fractions. The majority of p57v-rel was found in the cytoplasm. Examination of REV-T transformed lymphoid cells labeled with 32Pi revealed that the majority of the phosphorylated form of the v-rel protein was also found in the cytoplasm. Indirect immunofluorescence of REV-T transformed cells gave a diffuse cytoplasmic pattern indicating that p57v-rel was not associated with any discrete cellular organelle. The distribution of p57v-rel was similar in REV-T transformed lymphoid cells labeled with [35S]methionine for short and long periods of time, suggesting that p57v-rel is a soluble cytoplasmic protein throughout its lifetime. The v-rel protein was phosphorylated when immune complexes precipitated from transformed cells with the immunoglobulin fractions obtained from antisera against the amino-terminal, middle, and carboxy-terminal regions of v-rel were incubated with [gamma-32P]ATP and Mn2+. The phosphorylation of p57v-rel in the in vitro immune complex kinase assay was inhibited when the immunoglobulin-enriched fraction of these antisera was preincubated with the homologous v-rel fusion proteins. Preincubation with heterologous proteins did not block the phosphorylation of p57v-rel. These observations suggest that p57v-rel is associated with a protein kinase activity. Most of the kinase activity was found in the soluble cytoplasmic fraction of transformed cells. The transforming protein encoded by v-rel is a relatively stable protein with a half-life of approximately 7 to 8 hr in transformed lymphoid cells.